text:
How to make the measuring grid larger?
When starting the blender, there is always a cube on the floor. The floor is actually a grid. My question is how to make this grid bigger so that we can measure big stuff?

I assume you are talking about this grid in perspective view...

Since your goal is to measure things relative to a grid, you can use orthographic view to do that, which makes it easier to construct geometry. Here's how it looks like:

This is the same cube in orthographic projection viewed from above. It is easy to get there. Assuming you are still using the default key mapping (you havn't changed the keyboard settings) you can get to orthographic by pressing 5 on the numpad and then pressing 7 on the numpad for top view, and 3 or 1 on numpad for other directions.
So you insert a plane, which is 2x2 initially, as you can see.

Now I scale it to 50x50...

That just go big. Now I get to orthographic view with numpad 5...

And now I switch to top view...

As you can see now, the grid is now spread in all directions infinitely. You can zoom out to see that...
This is the same 50x50 plane.

What you might complain about is that you can't see the grid inside the plane? Well, for that just switch to wireframe (*by pressing z). Here's how that looks like...

That's one way of getting what you want.

Thanks very for you help. It is really appreciate if you can help me out of this question. In the first pic in your post, there are 16 * 16 grids under the cube, how could we get, say, 32 * 32 grids? In my case, I added a plain, and scaled its size out to 50 * 50, so that I want more grids to measure it......

Like I said, you can use the orthographic view to measure your plain. Let me show you...

I just made an edit to give you an example. Happy modelling!

How do you actually insert a plane?

OP asked "...how to make this grid bigger so that we can measure big stuff?". That can be easily done, but this answer doesn't explain how to do that. Maybe it's just because this answer is very old and the grid scale is a new feature? Currently, there is a much better/easier way.

You can change the size of the grid to accommodate your needs, or you can change the scale of the whole scene.
To change the scale of the grid in the 3D view.
For 2.8X Open the overlay controls.

And change the scale and number of subdivisions.
For 2.7X
Press N to reveal the properties shelf.
On the Display section you can change the grid floor number of lines and scale.
The left side of the screen will show info on the scale of the units used.
From the wiki:

Lines defines the number of lines that will make the "floor grid" up. If N is the number defined, there will be a total amount of N/2 lines at each side of X and Y axes. For odd values of N, the amount of lines will be rounded down.
Scale defines the distance between grid lines, either in the "floor grid" and the infinite grid.
Subdivisions defines the amount of lines into which the infinite grid should be subdivided. Level of subdivision depends on zoom, in predefined orthographic views.

To change the scale used for the scene:
Other way to deal with large (or very small) objects is changing the scale on Properties->Scene->Units->Scale

Note that changing the scale for the scene in the Units Section will affect the size of the grid, but changing the size of the grid in the 3d viewport will not change the scene's scale.
Besides the floor grid, Blender has some built in measuring tools that you might find useful.
For 2.8, in Edit mode (Tab), open the Overlays section and you can choose to enable the boxes for Edge Length, Edge Angle, Face Area or Face Angle.

For 2.7X, in Edit mode (Tab), enable the numeric panel (Kbd>N) and look for the Mesh Display section, to enable display of edge and face info of an object.

When dealing with very large or very small objects they might seem to disappear from view due to the clip distance on the viewport. If that happens you might need to change the start and end clip values.
See this question: Why does part of my model disappear when I zoom in on it in the 3D Viewport?

perfect!  a 2.8 version question!  Thanks, just what i needed!


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Which operations are expecting input in radians and which in degrees?
Triggered by this question (unfortunately the OP didn't elaborate on the context), I'm puzzled now: which operations are done in radians and which in degrees?
In the 3d window all navigation is in degrees (presuming the Units selected for the scene are indeed degrees), but from what I read, internally Blender is using Radians, leading to some confusion when setting drivers, constraints, modifiers or texture mapping. So far I haven't run into any issues but I'm just trying to understand the logic behind it.

As far as I know, blender uses radians internally everywhere. Only the UI appears in degrees.

It seems blender uses radians internally everywhere as of 2.70, except for a few cases listed in the release notes:

Blender internally stores angles as radians (even though they are presented through UI as degrees), but in a few places degrees were still being stored, which added internal code clutter, and could generate bugs like T32843.
Here are affected properties:

Data:

Lamp.spotsize:
  Game engine exposed this setting in degrees, to not break the API here I kept it as such (using getter/setter functions), still
  using radians internally.
Mesh.smoothresh:
  Didn’t touch to this one, as we will hopefully replace it completely by loop normals currently in dev.

Modifiers:

EdgeSplitModifierData.split_angle, BevelModifierData.bevel_angle:
  Done.

Postprocessing:

WipeVars.angle (sequencer’s effect), NodeBokehImage.angle, NodeBoxMask.rotation, NodeEllipseMask.rotation:
  Done.

BGE:

bConstraintActuator:
  Orientation type done (the minloc[0] & maxloc[0] cases). Did not touch to limit location type, it can also limit rotation, but it
  exposes through RNA the same limit_min/limit_max, which hence can be
  either distance or angle values, depending on the mode. Will leave
  this to BGE team.
bSoundActuator.cone_outer_angle_3d, bSoundActuator.cone_inner_angle_3d:
  Done (note I kept degrees in BGE itself, as it seems this is the expected value here...).
bRadarSensor.angle:
  Done.

You can input a value in either radians or degrees by appending a "d" suffix (for a value in degrees) and a "r" suffix (for a value in radians) to the numerical value.
"1.5913513r" => in radians
"1.5913513d" => in degrees
For example, if you click the X-axis rotation button of an object to input a rotation value manually, and write "1r", after you press ENTER to commit the value the button will show 57.3º. Hovering the mouse over the button will show a tooltip saying "radians: 1.000000" (and 57.3 degrees is the approximate value of 1 radian).
You can use this when editing drivers, rotations etc. in case you prefer one unit over the other, and Blender will do the conversion for you.

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/

sort: votes


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Weird fuzz/shading error on a render of a house model. Help?

As you can see in the render above, there is some weird fuzz on the side of the house, as well as some sort of spiky shade in the triangular area. I would like to know what causes that fuzz.
More importantly, I want to fix the triangular area shading error. It really ruins the look of the house.
Here is another view of it.

How can I fix the fuzz shading and the shading error in the triangular part of the roof?
What is causing this? I already tried removing doubles and recalculating normals. The lighting is a combination of Environment Lighting of 0.760 and an Area Lamp shining directly on the front of the house.

Cycles or internal..?

Blender Render. (Internal)

That is Z fighting, and we have a plethora of questions on that on this site. Somewhere you have duplicate faces which is causing that problem.

The problem on the triangle of your house is that there are intersecting meshes. To fix the issue, go into edit mode and hit W>Remove Doubles. also make sure that you don't have an duplicate objects.
To fix the noise, change this setting:

The higher you set it, the less noise you will get, and the longer your render-times will become.

If this fixed your problem, please press the checkmark to mark this answer as accepted.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


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Handler existence checking
I need to run a script several times, which among other things adds a custom function to a handler list. How can I check that it doesn't eist already, so as not to have several identical functions in my handlers list, without clearing the list altogether?
This doesn't work.
import bpy

def test(self):
    print('test')

if not test in bpy.app.handlers.render_pre:
    bpy.app.handlers.render_pre.append(test)

You can use a list comprehension to check if your function already exists:
def myFunc():
    """Your function"""

if not myFunc.__name__ in [hand.__name__ for hand in bpy.app.handlers.save_pre]:
    bpy.app.handlers.save_pre.append(myFunc)

It'll get the function's name from the pointer for each function in your handler list. Then, you can compare it to your function's name.
[hand.__name__ for hand in bpy.app.handlers.save_pre]

It's equivalent to:
handlerList = []
for handler in bpy.app.handlers.save_pre:
    handlerList.append(handler.__name__)


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How to limit a bone between other two bones, for scale and position
I have this situation:

I want the bone "A" to always be between the other two bones, extension included. This bone receives user movement, grab and scale, using any number of extra bones.
I already tried to give bone "A" constraints like Floor and that worked nice, but it doesn't work for the other handle of the bone.

This second image show an auto adjustment making this effect, using Floor and  Stretch, but the interaction bone (the selected one) lacks for limits in it's extreme, making it imprecise.

I'm not entirely sure what you're asking, but I'll take a guess:
If you want A's base to be at B's base and A's tip to be at C's base, you might benefit from drivers.
Unfortunately, the expressions to map from B and C to the proper pose for A would not be trivial.
Also, blender has some shortcomings in its dependency system that prevents intra-armature drivers from being calculated correctly in some circumstances.


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What does "Baking" mean?
I want to make some cool items for Dota 2 and I'm reading a guide. There are some tips about baking  etc. but I can't use them, because I don't even know what baking means. Can somebody explain this, please?
Thanks for all answers.

Here's an article that talks about that: https://cgcookie.com/2016/05/03/big-idea-baking/?ref=3

There are a couple different kinds of baking.
Texture baking
Baking could mean that you calculate specified data, and save it to a texture, which then you use in your material.
The purpose of baking is to save in render times, because Blender recalculates all shadows, lighting and what not, every single frame, which results in a lot of time wasted time for long animations.
However, render baking should only be used on objects which don't move, or aren't affected by other moving objects (except for the camera), otherwise the viewer will notice that shadows are moving when they shouldn't be, or are not moving when they should, breaking the illusion of realism.
Physics baking
Baking can also mean precalculating physics simulations such as Cloth or Rigid Body. For this Blender saves them to a file, which then loads when rendering or playing back the animation so that the physics don't have to be recalculated every time.

There is also AO (Ambient Occlusion) baking, it will apply the AO on your textures so they wont have to be recalculated, like in this video https://www.youtube.com/watch?v=9M6QBCLP04M


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Remove empty vertex groups?
Is there an easy (non scripted or standard script) way to remove all empty vertex groups (weight is zero).
Is there an easy way to remove all empty vertex groups vertex groups regardless of current weight assignments?

Do you mean remove the vertex from the vertex groups? or remove the vertex groups which are not used by any vertices?

@ideasman42 - remove the vertex groups.


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Motion Tracking. What do the graphs represent and how are they useful?
After tracking things on a video clip or image sequence, I get a graph with green, red and sometimes blue lines.
What do those lines represent, and how are they useful to get more accurate tracking or a better camera solution?

see also http://blender.stackexchange.com/questions/13663/how-to-see-bundles-and-back-projecting-points-of-different-colors/13670#13670

The red and green lines on the graph show you the speed of the trackers at a given frame. Green is vertical movement, Red is horizontal. The red and green curves will always start at zero in the first frame of the scene, and will move away from zero as the tracking points change position on the following frames. Objects closer to camera will move faster than those far away, so the speed in trackers in the foreground will be greater and objects far away will tend to stay closer to zero.
The curves are useful to see if particular trackers are moving differently than the average. A line that spikes way out of the norm might mean a tracking error, like a tracker slipping out of place, or maybe it means that an object is moving differently than the rest, and shouldn't be part of the overall camera solution. You can manually edit the curve by selecting a point in the curve and dragging it or deleting, that will affect the corresponding tracker on that particular frame.
In this example most of the trackers follow the same pattern. The green line that strays from the norm is a tracker that is wandering off. By manually moving the trackers or retracking with different parameters you could get the curve to match with the rest, but in most cases is better to re-track or find a different section of the scene that can yield more accurate tracking.

Once you have done your tracking and hit the camera solve motion button, a bunch of blue lines will appear, They represent the reprojection error for each tracker.

"The reprojection error is a geometric error corresponding to the image distance between a projected point and a measured one" (wikipedia).
Blender wiki says:
"Reprojection error means the average distance between reconstructed 3D position of tracks projected back to footage and original position of tracks. Basically, reprojection error below 0.3 means accurate reprojection, 0.3-3.0 means quite nice solving which still can be used. Values above 3 means some tracks should be tracked more accurately, or that values for focal length or distortion coefficients were set incorrectly."
The blue curves cannot be selected or edited directly on the graph window, but if you select a tracker on the tracking window the corresponding graphic will turn a darker blue, so you can see at what frame the reprojection is failing.
Finding the trackers with the highest reprojection errors is easier on the dopesheet for tracking data. It has a way to sort by Average error and you can see the numbers right next to the trackers name.

Finally, the lonely blue line that comes out when you click on the film strip is the average per frame error.
This curve is available only after pressing camera solve and is not editable.
This is the one line that you want to be as flat as possible and as closer to zero as you can. The high points will show you where in your shot you are having inaccurate tracking.

For general tips on motion tracking please read this post: How can I get better results when doing camera motion tracking?

Very interesting. Is there anyway to get (within Python) the actually X,Y displacement of the marker?

@Fabrizio I don't know, but I think it's worth asking that as a new question.

@FlorianB Those curves are there as reference, and as tools to better guide the trackers. They are not editable like animations in the graph editor or the dopesheet

@cegaton This answer was most helpful :)


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How can I find out how many triangles are in my model?
When I want to make some item, e.g. for a game, there's big chance for some triangle limit.
Is there some way how to find out how many triangles are in my model?

Select your object, and go into edit mode (Tab). In the info bar it will say how many triangles are in your object.

In object mode it will tell you how many triangles you have in the current layer(s).

In Blender 2.9+ you might need to right click the bottom bar and enable "Scene Statistics" to see this info.


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Mirroring object across global axis using mirror modifier?
I'm having trouble mirroring an object across the global X axis. As it stands the mirror modifier uses the local object center.
Is there any way to use global axis as the pivot?

Set the Mirror Object to any object (e.g. Empty) placed at [0,0,0]  with no rotation.

I quickly misread that as "leave the mirror object empty". For anyone in my shoes, you will create a new Empty object on the scene which you set at 0,0,0 and then use that object as the Mirror Object.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


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Python: remove driver for deleted shapekey
I'm trying to delete shape key drivers using Python, to clean up scenes. However, I cannot delete some drivers for previously deleted shapekeys:
driver_data_path = bpy.context.object.data.shape_keys.animation_data.drivers[0].data_path
bpy.context.object.data.shape_keys.animation_data.driver_remove(driver_data_path)

brings up this error:
Traceback (most recent call last):
  File "<blender_console>", line 1, in <module>
TypeError: bpy_struct.driver_remove(): property "key_blocks["Key 1"].value" not found

What I understand is that the data_path is an rna path, which is changed to key_blocks["..."].value when the shapekey is deleted. But then it cannot be found by driver_remove()...
Is this a bug, or is there another way to delete drivers?

As far as I am aware, when the item with the driver is deleted then the driver will also be removed.

I thought so too, but it appears not to be the case, at least with shapekeys.

Seems to be a bug. bpy_struct.driver_remove should not rely on the existence of data_path or the removal of a key_block should also delete related drivers. The data_path attribute of the driver is not read-only by the way.


text:
How to delete recorded position of mesh on animation timeline?
I've got problem with my animation. I've got a sword in my scene, but I somehow animated it so that its handle starts falling down when I play through the timeline, and I don't know how to delete this.

Look at the picture, there's some orange line at timeline bar - that's what I want delete.

You set the handle as a rigid body. The yellow line in the timeline shows you how much of the physics Simulation is cached. To delete the rigid body and all of the motion calculated from it Select the handle, then in the physics tab of the tool bar press remove.

You can also get to the physics settings in the physics tab of the properties window.

Select the frame where the line, called a keyframe, is(the name of the object, in the bottom left corner, will become yellow) and press Alt + I.


text:
How to animate the Displacement of the Displace modifier
I'm trying to animate a flag but I want to avoid using Cloth or any Physics simulation. I like the deformation I get by using a Displace modifier controlled by a procedural cloud texture. If I could animate the texture so it moves across the flag I'd be happy.
Is there a way to animate the coordinates of a procedural texture used by the displacement modifier?

Blend file here

Related: http://blender.stackexchange.com/q/8138/599

@gandalf3 That that question is not really the same thing...

@someonewithpc It's not, but it's a similar effect. (which is why I just commented it as "related", and not a duplicate)

I had indeed read that question, and maybe could have connected the dots. But maybe someone else will find this useful

It's actually pretty easy; Just create an Empty (While in Object Mode, press Shift + A>Empty>Plain Axis), map the displacement to the Empty's Coordinates, by selecting "Object" for the Texture Coordinates and then select the Empty for the "Object" field.

If you then animate the Empty, the Texture will move as well, thus modifying the Displacement.


text:
Calling delete() operator after revert_mainfile()
I have a script that tries to derive several blend files from the same source file. However after a while I realised that the delete() operator apparently doesn't work after reverting the file. I could nail it down to this, that can be run with the default startup scene.
import bpy

# if this line is removed, delete() behaves as expected.
bpy.ops.wm.revert_mainfile()

bpy.context.scene.objects['Cube'].select=True
bpy.ops.object.delete()

Expected result: Cube should be deleted.
Actual result: Cube is selected, but not deleted
Feature? Bug? Something I don't understand about how scripts operate when loading/reverting files?
This can be tested by copying the script in a text window and hitting 'Run Script'
EDIT: It's been suggested that I should refresh the UI to see the result. This is irrelevant to the problem. (As I did) you can confirm that nothing was deleted programmatically.

It is basically a timing issue: your code below revert_mainfile() is called before the scene is ready, it's simply too early.
A load_post handler alone doesn't help either, the argument passed to this callback is None.
If you register a persistent load_post handler, which sets up a scene_update_pre handler, the execution will be delayed until the scene is ready:
import bpy
from bpy.app.handlers import persistent

def scene_update_callback(scene):

    # self-removal, only run once
    bpy.app.handlers.scene_update_pre.remove(scene_update_callback)

    ob = scene.objects.get("Cube")

    if ob is not None:
        bpy.ops.object.mode_set(mode='OBJECT')
        bpy.ops.object.select_all(action='DESELECT')
        ob.select = True
        bpy.ops.object.delete()

@persistent
def load_post_callback(dummy):

    # self-removal, so it isn't called again
    bpy.app.handlers.load_post.remove(load_post_callback)

    # use a scene update handler to delay execution of code
    bpy.app.handlers.scene_update_pre.append(scene_update_callback)

if __name__ == '__main__':
    bpy.app.handlers.load_post.append(load_post_callback)
    bpy.ops.wm.revert_mainfile()


text:
How can I disable one OpenCL device
I have successfully enabled the experimental OpenCL support and my scene (surprisingly) renders fine, without any crashes or artifacts.
My setup consists of two AMD cards and an Intel CPU. Choosing either card as a GPU Compute device works fine. Enabling all devices together also works, but (presumably due to different cycles feature set supported) some tiles are differently lit. Moreover, the render is slower, as for some reason the GPU's wait for the CPU to finish before going on to the next tile.
The question is, is there a way to enable both GPU's but not the CPU as a compute device?

There is currently no way to do what you want from blender.
You can however set CYCLES_OPENCL_TEST to "GPU" and see only devices in blender that claim to be a GPU.


text:
Moving in steps or smoothly, changing the default settings
By default when you are grabbing part of a mesh you can move it around smoothly or you can press the Ctrl key to move it in steps.
Somehow I pressed something I wasn't supposed to and now it moves in steps normally and I have to keep Ctrl pressed to move selections around smoothly, how can I return to the default settings?

Sounds like you have turned snapping on.
Holding the Ctrl key toggles on snapping temporarily. I presume you have accidentally turned snapping on, meaning the Ctrl key will now toggle snapping off.
You can turn it off my clicking the magnet icon in the 3D header toolbar:

(The image shows snapping is turned on)

Thanks for the quick answer! As I thought it was a trivial problem, but being a beginner I can't quite find things in all the toolbars...

Feel free to mark this question as 'Accepted' if you find this answers your question. See: http://stackoverflow.com/help/someone-answers

I couldn't accept it earlier for the time limit


text:
Edges with mean crease set to 1 are still rounded by a subsurf modifier
I am a complete beginner in blender, so my question may turn out to be trivial.
I have a cylinder with some square-ish elements slightly carved into it, as you can see in this screenshot

All of the edges of the squares have a mean crease value of 1:

However when i apply a subsurf modifier the result looks like this
.
What should I do to keep the edges straight when applying the modifier?

Hmm, rereading your question, you say all the edges are creased. Can you post a screenshot in Edit mode so I can remove or update my answer accordingly.

you need to crease the inner corner edges.

@iKlsR: done, as you wrote the problem were the inner edges, thanks for the quick answer and the bonus tip!

Make sure the inner edges are creased at the corners as well. For example:
With only outer edges creased

With inner edges creased

As a bonus, you might want to drop an Edge Split modifier on as well to get your object smooth and remove the stretched shades that creasing and subsurf will produce. Also see How to smooth shade an object while retaining hard edges?.


text:
Is it possible to have different background images for different visible layers?
The title is pretty self explanatory, I am modeling two object on two different visible layers and I have blueprints for both of them, however I cannot find an option to limit the visibility of a background image to only one layer

This isn't possible by default with the Background Images subset in the Properties panel, whichever image you have set to a view is what will show across all layers.
An alternative however is to use Empties with their Display type set to Image as detailed in my answer here. This way you can just move the specific empty with the blueprint to the layer with the object you are working on. To have this not obscure or interfere with your work, just open the Outliner and restrict these from being selected (the cursor icon).
(Notice that I switch from Layer 1 to Layer 2)

A similar method to the above is to enable the Import Images as Planes addon and create two planes, one for each image. These can be placed in any layer, and display of the images can be enabled or disabled separately for each image by using the outliner window, or by careful placement of the planes in layers, and enabling or disabling the visibility of the layer.


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How to register custom math function?
I need to create a script to define certain math functions. This script will not directly modify or create any objects. I will simply use them with the XYZ Math surface and/or the Z Math surface. Among other functions, I need a sgn() function (why on Earth it isn't part of python I cannot fathom) and an a^b function that can handle non-integer b for negative a.
Creating these functions isn't a problem. I already have, for use with drivers, and I know I need to register them there by
bpy.app.driver_namespace['<functionname>'] = <functionname>

But how and where do I register them to be able to use them. My guess would be
bpy.app.foo['<functionname>'] = <functionname>

But what should I substitute for foo here?
This is simply amazing. I've googled for days about this, and the answer is nowhere to be found. Everything is about modifying meshes and creating classes to extend blender's functionality with new addons.. I have no need for that. I may at a later time, but I don't know. Is there really no way to implement a standalone mathematical function and register it in a way that it's available to all aspects of the program?

Thanks, David, for that edit. That's almost exactly as what I wanted to appear, but somehow the  got lost. Don't know if I missed it during cut'n paste of if SE removed it.

Some clarifications. The functions I gave as examples, are JUST examples, that may be usable as oneliners in e.g. the A parameter for the XYZ Math surface object. But what about more complex functions, say a function that calls itself iteratively?

You first example line bpy.app.driver_namespace['<functionname>'] = <functionname> registers the function within the driver namespace and makes it available as <functionname> within any driver expressions.
From other areas of blender you can access it with it's full data path - bpy.app.driver_namespace['<functionname>'](3) calls that function passing a value of 3.
But that isn't the issue you have with the math object creation -
The XYZ math surface object allows you to enter an arbitrary string to define the surface of the object. As this also allows any python to be run it implements a security feature that prevents any functions not listed in it's safe_list from being run.
To get around this you need to do two steps, add your functions as a module and then import them into the addon and add the names to the safe list. Or you can adjust the usage of the safe list to allow any functions. You may want to duplicate the addon and adjust it so you have your own custom addon that suites your needs. You may also find it easier to define the calculations used and just input a few variables.
For a sign function in a on-line script you can use 1 if x>0 else 0
For a^b I don't see an issue -2**3.5 returns -11.31370849898476

The issue isn't calculating the values. The issue is defining names for them. And the second works when a is negative. I want a function that gracefully handles both positive and negative a. Something like if a < 0:
retval = -(math.fabs(a)b)
else:
retval = ab
return retval

@sambler I use squircles, and they involve the square root of (co)sines. I handle this by creating a quarter squircle, in the x>=0, y>=0 quadrant, then mirror it over the x and y axes.
The problem, that made me ask this question, is that I need to create three squircles, all with prime numbers of vertices. This could, of course, be solved by (slightly correcting) your oneliners, but it lead me to think one or two steps beyond that; the need for mor complex functions, that can't be expressed as oneliners. And what you're saying is that a new addon would be needed to accomplish that?

I managed to solve my current need with the help of your oneliners, and because of that I marked your answer as the accepted one. Thanks.
If you, or any reader, could point me to a good tutorial on scripting for Blender, I'd be very greatful. All those I've found more or less require good knowledge about Python. My programming skills are a bit rusty but moderately advanced, and mainly C and C++ and some VERY rusty Pascal knowledge. What little Python I know is rudimentary at best, and it's something I've learnt since discovering Blender about a year ago.

The main point is that for security reasons only a particular set of functions can be used, to expand that list the addon needs to be modified. Any python tutorial can get you familiar with the language, the official one is here, python3 specific tutorials are best. blendercookie has several most are free. For blender specific info the api reference is the best resource. Also use the auto-complete in blenders python console.

I just returned to this my very first question here, and I just spotted a little mistake in your answer. -2**3.5 does indeed return -11.31370849898476. However, what that does is calculate 2**3.5 then negating it, and (-2)**3.5 returns a complex number. The first one is what I wanted to achieve, but doing it in a script with a variable whose sign can be either + or - is trickier, and that's what I needed a sign function for, like this sgn(a)*(fabs(a)**b)).


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Multiple flames from one mesh
Is it possible to produce several small flames from different parts of the same mesh? I'm modelling a birthday cake with 42 candles, and in a weak moment I joined the cake and the candles into a single mesh (don't ask why, I honestly don't know). I created the candles by modelling one, which I used as a template object for a particle system, which I then converted into objects. Then, ¤#!& knows why, I joined it all, including the cake, together into one glorious whole.
Could I put a smoke domain around each candle, or do I need to separate them? Or could I even accomplish it with a single domain?
I save pretty often, so although I have Blender keeping five backups, I can't recover the individual meshes (my /tmp is a tmpfs, and I've rebooted since the "accident", so no quit.blend either).

Why not separate the candles from the cake? Try using P > Separate by loose parts.

@gandalf3 Yes, I know about that. But does each candle have to be its own mesh? If that's the case, I'll do it. Or rather just separate the top, including the wick, of each candle. I take it I'll need 42 smoke domains? If so, is there a shortcut to creating that many and placing them on the candles? The candles are randomly placed.

You can have multiple flame objects in one domain

@BlendingJake If you can (I don't know if it's possble), I'll mark it the accepted one. Thanks.

You can separate into loose parts like @gandalf3 said P > Separate By Loose Parts then have multiple flames in one domain, like this:

I'm already there. Setting up the F-curves for some moving objects as we speak. :)

@BlendingJake - mind sharing that theme? :)

@GregZaal http://blenderartists.org/forum/showthread.php?354395-THEME-Blued&p=2762878#post2762878


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Camera perspective in viewport is different to in render
I want my image to look like image 1, but when I render, the result is image 2.
Why is the viewport different to the rendered output?

Please provide a blend file or a screenshot of the camera settings. These can be found by selecting the camera and opening the camera tab in the properties window

It's because you're zoomed in on the viewport, and can't see the edge of your camera.
In the viewport, use the mousewheel to zoom out until the edge of the camera shows up. Select the camera, and move the camera forward with G MMB


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Keyframing Physics Animation
I have a Rigid Body object that I want to be animated at a specific time. Can I animate it using the Blender Game engine? Also, is pressing P the only way to see it (can I see it using AltA)?

Ensuring that blender is set to "Blender Game" mode, ensure that the "record animation" check box is ticked in the Game menu.

Then hit
P to start running the game (it'll probably run slower than normal). After the length of the animation you want to record has been recorded, press Esc to exit playing the game. Press left/right on your keyboard, and you'll notice a key frame has been added to each object for every frame of the animation:

(Also notice that if you play the animation using AltA now, the physics will run as it does in the game engine as the position data has been applied to the objects using key frames).
If you want to delete part of this animation or shift all of the physics animation in time, enter the dope sheet window like so:

You can select key frames by pressing B and drawing a box around the key frames you want to select. When doing so, ensure that you select the key frames of the object that you want to edit the animation of, and not X,Y,Z location and rotation as that will distort the physics simulation. You can ensure you are not doing so by clicking on the arrows so that these options are not visible:

After you have selected the key frames of the object you want to edit, you can increase/decrease the speed of the animation using the S key and make the animation of that object occur later/earlier in time using the G key.

You can also delete parts of the animation by box selecting the key frames you want to delete from the animation as outlined above, and pressing the Del key:

This will mean that the key frames of the object's animation you have deleted will not run (essentially cropping the start and end of the physics simulation if that is desired)


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Cycles final render pitch black?
In solid mode with Material or Texture, it is shown fine.

But in the Render mode, everything is pitch black. I have a sun, and the Opacity of the scene is set to 100%.

I am new to using Blender, so I have no idea what is wrong.
If you could help, I would appreciate it.
If you need more information to help me, I would be glad to give it.

The sun lamp's position, inside the room, doesn't affect where the sun's light is actually emitted from, it only controls the direction. To quote the blender manual:

Sun lamps emit light in a given direction. Their position is not taken
  into account; they are always located outside of the scene, infinitely
  far away, and will not result in any distance falloff.

So the light is being cast onto the outside of your room and not getting through the walls to the inside. You can see this by looking at the outside of the room while in 'Rendered' mode of the 3D viewport.
To solve this, you can either disable the 'ceiling' from casting a shadow by changing the 'Ray Visibility' options on the 'Object' tab in the properties space:

Or, change the type of light from sun to something else, like 'Point' or 'Area', whose positions are taken into account. You can also just set any object to emit light, like a plane, by giving it an emission shader.

This worked, but I still want shadows. Is there a way to edit the walls so they are not affected by the lighting?

As I said, you can change the sun to a different lamp type.

This is a common issue, and without the .blend file, my first guess would be this:
You have clips in the Video Sequence Editor and under Render Settings > Post Processing you have Sequencer checked. Un-check that box:

Didn't work. And, I do have it stored in a .blend file.

@MrSquer I believe the reference to the blend file was the fact that we do not have access to your file, to diagnose via screenshots can be guesswork. You can use PasteAll to upload your blend file for us to inspect if you wish.

Ok. I added the blend file (http://www.pasteall.org/blend/32885)


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How do I speed up Blender Game animation?
I am using the Blender Game render for keyframing physics, but when I play it back, it is so slow (the keyframes are close to each other, the closest they can get, but it is still slow). Is there a way I can speed this up in the graph editor?
Also, and unrelated question:
After I keyframe with Blender Game, can I go back to Cycles Render without affecting the timeline?

Yes, you can switch back to cycles without affecting the keyframes. However note that there is a rigid body simulator built into normal blender now, so you don't need to use the game engine necessarily. The reason it appears slow is because the viewport defaults to 24 FPS, but the game engine defaults to 60 FPS.

@gandalf3 So if I increase the FPS, it will run faster..? Because I just need the physics frames faster

possible duplicate of Rendering animation speed

@MrSquer You are probably better off running the game engine at 24 FPS (you can change this in properties > World settings > Physics).

@RayMairlot The keyframes are one frame apart, so I don't think scaling will work really..

You can speed up the playback of the animations by increasing the 'Animation Frame rate' speed in the Render properties editor.


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Making a curved tube thinner or thicker without scaling its overall size
Is there a simple way to change the thickness/diameter of a curved tube without scaling its overall size?
E.g. scaling the minor radius of an already created torus without affecting its major radius or change the bevel width of a curve that has already been converted to a mesh.

Yes, in edit mode you can use Alt+S to scale along vertex normals instead of from the median point.
So you can scale this...

To this...

To this...

This also works for bezier curves as well, even without converting to mesh.

Wow, that is such a useful feature!

This isn't working as pictured here for me. Alt + S tends to want to scale a torus into an eye shape.

@user2867288  Make sure your pivot point is not set to 3D cursor or something like that.

Just wanted to add that this is the shrinken/flatten tool you can find in the sidebar, too.

FYI:  in more-recent versions of Blender, suggestion #1 is simply available by a "Shrink/Fatten" button on the tool pane when in Edit mode.  (It is equivalent to Alt+S, as it indicates.)

Try the following method.

Change Mesh Select Mode to Edge
Select Edge Ring
Select Edge Loop
Change Pivot Point to Individual origins
Scale

This may seem a rather tedeous procedure, but can be used on tube with ends.
Let's go through this on the mesh below.

1. Change Mesh Select Mode to Edge
Aim: To select edge loops individually.
hotkeys: Ctrl-Tab -> E

2. Select Edge Ring
Aim: Select one edge for each edge loops.
Hotkeys: Ctrl-Alt-RMB on one of the edges

3. Select Edge Loop
Aim: Select all edge loops.
Hotkeys: Ctrl-E -> P
Caution: Alt-RMB is usually used for edge loop select but cannot be for this method.

4. Change Pivot Point to Individual orignis
Aim: Manipulate each edge loop individually.
Hotkeys: Ctrl-Period

5. Scale
Aim: Change Size
hotkeys: S

Just add the solidify modifier(Modifiers tab>Add Modifiers>Solidify)
Adjust the thickness.
If you have a limited poly count just delete the internal mesh.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


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Modelling a Klein bottle
How can you model a Klein bottle, such as this one?

There are most likely several methods, and they probably all have both drawbacks and advantages. I will show how to use the XYZ Math surface for this.
First of all, unless you have already done this, enable the Add Mesh: Extra Objects addon. Go to user preferences (CtrlAltU), click the Addons tab, then Add Mesh. Make sure the check box for Add Mesh: Extra Objects is ticked, then click Save user settings.

Then Add > Mesh > Extra Objects > Math Function > XYZ Math Surface.
This is what you will see

The default object created by this is a snail shell. To get the Klein bottle, enter these equations. Just copy and paste from here.
X equation:
$$-\frac{2}{15}\cos(u)\left(3\cos(v)-30\sin(u)+90\left(\cos(u)\right)^4\sin(u)\\
-60\left(\cos(u)\right)^6\sin(u)+5\cos(u)\cos(v)\sin (u)\right)$$
-2/15*cos(u)*(3*cos(v)-30*sin(u)+90*cos(u)**4*sin(u)-60*cos(u)**6*sin(u)+5*cos(u)*cos(v)*sin(u))

Y equation:
$$-\frac{1}{15}\sin(u)\left(3\cos(v)-3\left(\cos(u)\right)^2\cos(v)-48\left(\cos(u)\right)^4\cos(v)+48\left(\cos(u)\right)^6\cos(v)\\
-60\sin(u)+5\cos(u)\cos(v)\sin(u)-5\left(\cos(u)\right)^3\cos(v)\sin(u)\\
-80\left(\cos(u)\right)^5\cos(v)\sin(u)+80\left(\cos(u)\right)^7\cos(v)\sin(u)\right)$$
-1/15*sin(u)*(3*cos(v)-3*cos(u)**2*cos(v)-48*cos(u)**4*cos(v)+48*cos(u)**6*cos(v)-60*sin(u)+5*cos(u)*cos(v)*sin(u)-5*cos(u)**3*cos(v)*sin(u)-80*cos(u)**5*cos(v)*sin(u)+80*cos(u)**7*cos(v)*sin(u))

Z equation:
$$\frac{2}{15}\left(3+5\cos(u)\sin(u)\right)\sin(v)$$
2/15*(3+5*cos(u)*sin(u))*sin(v)
U min: 0
U max: pi or (3.141592653589793)
V min: 0
V max: 2*pi or (6.28318530718)
U steps and V steps control the number of vertices in each direction, the same as the number of segments and rings on a UV sphere.
If you enable U wrap, the opening of the bottle will be closed. You decide which you prefer. If you enable V wrap, some vertices will be lost, but I haven't been able to find where. I don't know at all what Close V does. It doesn't change either the appearance or the number of vertices and faces.
As you can see, these equations are very complex, and this has the drawback of making them difficult to modify. I will try to show you how to overcome that, using proportional editing and a scaling technique I learned from the answer to my own question in this thread: Making a curved tube thinner or thicker without scaling its overall size
Go into Edit mode, and select all. Remove doubles (W R). Deselect all and make sure Limit selection to visible is disabled.

Make sure proportional editing (O) is set to Connected and proportional editing falloff (ShiftO) is set to smooth.
Select the vertices you want to modify.

If you want to make any part of the mesh bigger or smaller, Shrink Fatten (AltS) is the tool. Scroll the mouse wheel to change the size of the sphere of influence of the proportional editing.

If you want to move any part of the bottle, keep proportional to its aforementioned settings, select the parts you want to move and drag them to where you want them. Like so:

Repeat steps 2 through 4 until the bottle is to your liking.

You're done.
N.B. A Klein bottle is self intersecting, and therefore won't work as a fluid container with the current fluid simulation of Blender.

Very nice, now you only have to show us how to ge consistent normals ;)

@maddin45 I have tried and tried, to no avail. :(

It was a joke ;) There is no way to get consistent normals on a Kleine bottle (or even a Mobius strip) because at some point the inside will become the outside. I might work if you first give the surface some thickness by applying a solidify modifier, because then the surface would flip twice. I haven't tried it though.

I'm working on an animation where I'll use a cheat. Using an opaque bottle containing a fluid outflow and making the vertices by the opening an inflow. This way, when the bottle is standing, the fluid will disappear into the outflow, and when it's tilted the fluid will flow as if the bottle contained it. In theory at least. I'm not quite there yet.

Just noticed that an inflow can't use vertex groups (hadn't actually come to that specific bit until now), so perhaps a fully transparent object as an inflow just at the opening and an outflow just beneath the inflow.
And doesn't the solidify modifier also require consistent normals? At least I get very bad results when trying to solidify.
Anyway, this is getting OT now, as this was about the actual modelling. I may have to post another question to explore this further. One that I can't answer myself.

Yes you are right, the solidify modifier also needs consistent normals. My bad. But have you tried to 1. split the model along one edge loop, 2. recalculate the normals, 3. apply the solidify modifier and 4. merge the result back together?

No, I haven't tried that. I may later, but first I have a few simpler ideas. Basically about the size and shape of the inflow and the outflow. And most of all, I have been sadly neglecting my sister's birthday greeting, on which I was working when I got stuck with this thing. (I still have time for the greeting... Fortunately).

@SixthOfFour thank you for the great question and answer about Klein bottles. I used your method and made one here.

@David That's great. :) I've been fiddling to and fro with one that can actually hold its liquor.

Beside math, there can be a simpler way to model it:

Add Bezier Curve, do not make it cyclic, then tweak points;
Adjust Radius (Select one or more points, AltS)
Convert to mesh (AltC - Convert Mesh from Curve/Meta/Surf/Text)
Bridge the two open loops (W - Bridge Edge Loops)
Cut off the intersect faces: Mesh > Faces > Intersect, then delete them. (optional)

P.S.:
The consistency of normals has to be broken in this case. It is very interesting, which means you cannot make thickness simply by applying one Solidify modifier. It actually isn't a 3-dimensional thing.

A good one, no doubt. :) Upvote for that.

That's a smart use of "Bridge Edge Loops". I'm sure I will borrow that technique for something someday. :-)

"Beside math, there are simpler ways..." I was getting all geared up to not believe you and then looked further, and did a quiet face-palm. That's really nice! To make a finite-thickness walled object you have to make two copies - one moving "out", one moving "in". The one that starts "out" will end in, and vice versa. Then delete the original and splice the two together.

Since it came up in the comments about the normals being a total mess after Remove Doubles is used because the mesh folds through itself I have posted an answer here on how to fix this.
Recently a tool named Intersect was added that can fix this issue by performing what is similar to a Boolean Intersect operation except that this tool works in Edit mode and can handle self-intersections.
The first image shows the messy mesh after Remove Doubles is used.

Now press spacebar and type Intersect and click that entry to activate the tool and change the menu entry to Self-Intersect.

Next use Remove Doubles again.  This may require an adjustment to the Merge Distance.
Once that's done you can select everything and use Ctrl n to Recalculate Normals and it should look good.(aside from the quads meeting up with nGons.)
There are also some interior faces created at the junction which should be deleted.
Here's the result rendered with a glass shader and a bit of volume.

And an upvote for that one too.

Looks like this is rendered as a solid. The Klein Bottle is actually hollow. The messed-up normals are then a topological necessity, the Klein Bottle being famously non-orientable. So, the intersect tool actually doesn't the physically “right”, but mathematically wrong thing.


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Wrapping a 2D net over a 3D object
Is there a way to have a 2D mesh wrapped around a 3D object. Like this:

The red part is a flattened knot, which I mapped onto the surface of the blue part. In this specific case I used math to achieve it, but not all shapes can be easily expressed as formulae. What other ways are there?
I tried using physics, making the blue part a passive rigid body and the red part a soft body falling onto the blue part, and it seemed to work beautifully. But when I tried it again now, I realised that it doesn't do what I'm after. The net and the object onto which I want to wrap it already have the same X and Y dimensions, which is how I want it. I only need to remap the Z coordinates.
Another idea that comes to mind, would be generating a texture from the Z coordinates of the blue part and use that texture with the displace modifier on the red part. Is this possible?

use shrink wrap modifier?

I honestly didn't think of that one. I tried it just now, and it doesn't do exactly what I need. And had to look again at what the physics does, and it actually fails in the same way. I didn't close enough the first time, because I couldn't find a way to get it to remain. Both curve the object, so that the vertices move along all axes, not just the Z.

You can use a conbination of Mesh Deform and Cloth simulation with proper settings.

Create a grid plane to cover the whole net;
Add Cloth Simulator to it, then Solidify modifier;
Tweak settings of them;
Add Mesh Deform modifier to the net object. (use higher Presision value if necessary, then Band)
Then play or bake the final shape. Delete the grid mesh (optional).

Example File

Thank you for that. Where I am, it is currently so late that it's actually early, and I'm off to bed. I will try this out when I wake up.

I upvoted and accepted your answer. It does change the X and Y coordinates as the net wraps around the collider, but it certainly feels like it gives me more control than the shrinkwrap, suggested in a comment to my question, especially in the case where I bevel the net before wrapping it. Thanks a lot for your effort.

Sure. You can also do manual control instead of simulation (In that case, a Lattice modifier works better). I believe both leave you a lot of flexablility. :)


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Animation in viewport suddenly becomes very slow
I was working on a grass animation with a wind force field.
First the animation in the 3D view was running at normal speed (~20 fps) then I adjusted a few settings like Stiffness and Bending. And now the animation is running very slow (~0.8 fps).
I loaded an old save file that worked just fine before, but even there the animation speed is now achingly slow.
Do I have to clean up or refresh something I don't know about?
Is this a known problem and is their a way to solve it?

An example file at least would be very helpful for others to see what's going on. You can upload it to Pasteall.org.

Blender caches things like cloth physics so that they can be played back quickly, but changing settings will invalidate this cache. The only thing to be done is to re-simulate and cache it (by playing the animation through once) or bake it (by pressing Bake in the cache panel). Baking will simulate and "lock" the cache and prevent it from being invalidated, but as such you won't be able to change settings.

Thank you for your answers. I tried playing through the animation again and baking it. But even with all the frames in memory there is still no change :/ I uploaded an example file http://www.pasteall.org/blend/32947


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Texture Changing with Keyframes
I have created UV textures for lip-syncing, but I do not know how to change the textures with keyframes. So say I want to go from a neutral face to a transition face on the next 5 frames to a speaking face. How would I do this?
Edit:
I am using Blender Render. Here is a screenshot:

@NoviceInDisguiseGraphics what? lol

I don't know if this is what you're looking for but it may help you: http://blender.stackexchange.com/questions/18363/animating-eye-texture-in-a-head-mesh


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How to make a rusty texture?
I'd love to make a rusty texture for specific part of my model (look at the picture), through texture paint, but I don't know how. It seems pretty lenghty and hard for me, in case of making it manually. So my question is - is there any easier way to make rusty texture only for part of my model?

If you want a realistic looking rust material I may recomend you Blender Guru's tutorial on how to do it. Here's a link: http://www.blenderguru.com/tutorials/create-realistic-materials-with-cycles/#.VHR-mYuG9p8

I don't really need to have it realistic, and tutorial you sent is in cycles, I accidentaly started this in Blender render, so I'll finish it there to don't screw up something.

Is there a particular reason you want to use texture paint and not use a rusted metal texture? You can also try something procedural.

You can make use of the Brush Mask textures with either a cloud, stucci or musgrave procedural texture set to View Plane, and Rake and Random in the texture mask brush settings in the tool bar. Using this, select your color under your brush with S and then set your brush blend mode to 'multiply' and lower the strength a bit. You can knock in some textured spots, and then switch your blend mode to 'screen' or 'add' to break this new textured area up with some illusion of depth. If it gets too strong, switch back to 'mix' blend mode and tone it down.
Using photo textures as a reference is actually best here, looking at the kinds of patterns that occur with the oxidation. Sometimes you just get pits showing up from under the paint, sometimes you have a whole area of voronoi-like shading aroudn deep wells. As the painter, you are the one in charge here.


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Blender 3D Game Projects?
I am just beginning learning to use Blender and I was wondering if some of you have some sample game projects. Or if you know any good book, forum or videos tutorials for the last version of Blender (2.72). Thanks.

http://www.yofrankie.org/download/

See http://blenderartists.org/forum/showthread.php?256650-Quality-Blender-Games-LINKS for a comprehensive list; we should add this to the resources question: http://blender.stackexchange.com/questions/15355/resources-for-blender

Check this list of Blender games on Blender-Artist

I'm voting to close this question as off-topic because it is asking for links to tutorials.

I would recommend that before you learn to use the blender game engine, you learn to use the normal blender engine so you can get the hang of the basics and it hugely minimizes some of avoidable mistakes - and if my experience was anything to go by, you'll make a ton.
I would recommend that you mess around with it, try to set yourself basic project and you'll slowly learn how to do new things and old things more efficiently.
Here are a few websites I would recommend:

https://www.youtube.com/user/CGAstym
https://www.youtube.com/user/GlebAlexandrov
http://www.tutorialsforblender3d.com/Game_Engine/Tutorials_index.html
https://www.youtube.com/playlist?list=PL9057AB8E3C66AE80 and archived

authors: Олжас Касымов


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Offsetting flames and/or smoke from the emitter
I've tried a few times to get emitted smoke and fire to appear slightly offset from the emitter, like for example a gas weld or a flamethrower. I've played with vorticity, temperature difference, density, speed, flame rate and practically every other setting whose name even remotely indicates that it may make a difference. All to no avail. I've also tried to add wind with various strengths and directions, and making a larger portion of the fire colour ramp transparent.
As you can see in this image, Suzanne emits fire from her eyes and whatever that heart shape is meant to represent (mouth or nose?).

I want a small gap before the flame actually appears, similar to what can be seen here.

How, if at all, can this be achieved? I'm using BI.
Blend file for the Suzanne image: http://pasteall.org/blend/33192

You could try making a fake emmitter. Basically an object that has faces where you want the smoke emmited.

That is, of course, an option. However, I was hoping it could be done without adding more faces. I will consider it though. I upvoted, and I'll accept if, after experimenting further, no other solution magically appears.


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(Placement of hair)Hair particles ignores Weight Paint and Vertex Groups
I'm trying to add hair to my model in Blender, but when I try to make the hair emit from only one place by using the tools in "Object Data: Vertex Groups" or by using Weight Paint, the hair doesn't move to where I painted, but stays in the same place. I tried using both version 2.67 and 2.72. What am I doing wrong?

You need to set the Particle System such that the Vertex Groups affect the density of hairs. On the particle system tab, scroll down to the subsection Vertex Groups and add your group to the density.

Assign the selected vertex group and name it.

Go to the 'Particles Menu' header and input the vertex group name in the Density window (located in 'Vertex Grops' panel).

Edited:
I've checked your model and found the solution. In your case you have to place the 'Particle system' modifiers over the 'Mirror' modifier. As you can see below, the beard and tail particles are now assigned to the right vertex groups.

I can advise you few more things. Before adding the hair particles to your model, make sure that:

it has a good topology
the double vertices are removed (in 'Edit Mode' press W--> Remove Doubles)
the normals are facing the right side (CTRL+N in 'Edit Mode')
the location, rotation and scale is applied (CTRL+A in 'Object Mode')
there are no ngons, non manifold elements, interior faces (you can check it very fast using a 'Mesh Lint' addon)
the 'Mirror Modifier is applied

Thankyou for answering! I have already done that though, and that doesn't work :(

Hmmm...That's strange. You may post your .blend file via http://pasteall.org/ if you like, so we can see what's the problem and find a solution.

http://www.pasteall.org/blend/33133

(Trying to add a tail and some light "beard")

I analized your model and I think it need a little "clean up" :). Your mesh need to be clean before applying the hair. Please see an answer in this thread:
http://blender.stackexchange.com/questions/16489/problems-with-particle-hair-in-2-72-cycles
I'll try to fix your mesh asap, so you may apply the hair properly soon.

I wouldn't apply the modifiers, just make sure the use modifier stack checkbox in the particle settings is checked and you should be able to put the particle systems last in the mod stack.  See hair particle system not rendering properly on plane.

Thankyou very much to both of you! Checking the "use modifier stack" did it :)


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Can I get a more fine grained zoom in the UV/Image editor?
In the UV/Image editor, and consequently when viewing the render results, the zoom has pretty big increments. If I render at 1920x1080 or larger, I can get the image to fit almost perfectly to the viewport. However, if I render at 1280x720 (which I do occasionally), I either get a ~2.5cm space between the edge of the image and the edge of the viewport or the image gets cropped by ~0.5cm. Is there a way to get smaller increments?

I'd like to know about this in the node editor as well.. I suspect the answer will be the same

@ajwood Zooming on the nodes in the node editor? Or the background image?

@gandalf3 I meant the nodes themselves, so the + does the trick

You can press F to fit the image to the view.
You can also press the Numpad keys to jump to various zoom levels, e.g. Numpad 1 will zoom to 1:1.
You can see more options in Header > View:

You can use ⎈ Ctrl +  MMB to zoom in and out smoothly. Keep in mind you are meant to press the MMB and drag up or down to zoom in and out, respectively. This works in all editors which support zooming.
Another thing to keep in mind is that, for instance in the Movie Clip Editor, when set to Graph, there are two zoom axis - a vertical and a horizontal one - which can be controlled separately.
There is also another tool called Zoom to Border, which can be accessed through Shift + B. This let's you use something that looks like the Border/Box select tool, but instead of selecting, it zooms in to the specified area.
Note that in the Node Editor (more specifically in the Compositor), any other zoom method will zoom into/out of the nodes themselves. To zoom in in the background image (when a Viewer node is connected) you can use Alt + V and V to zoom out.
Adding to gandalf3's answer, you can press Shift + Numpad Enter, when looking through a camera in the 3D View, to make it match the zoom level 1:1.

Also a good one. I usually zoom with the scrollwheel, and I didn't even know I could zoom like that. Now I'm trying to decide which answer to accept.

I would have accepted both if I could (and I actually tried). Your answer was better in that it addressed my question in a more general sense, but gandalf3's answer gave me what I was after, namely fitting the image to the window.

@SixthOfFour Yeah, I noticed the little switcheroo that happened...

@someonewithpc Shift Numpad Enter doesn't fit the camera to the view, it zooms to 1:1.

@gandalf3 yes, that...


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Camera facing backwards when exported as FBX and imported to Fusion 7
Similar to this question: I exported a motion tracked camera and some geometry from blender to be opened in Fusion 7. I used the FBX exporter using the default settings (-Z Forward, Y up).
Scene in Blender

When I opened in Fusion, the geometry came in fine but the camera was facing backwards.
Scene in Fusion

I tried playing with the settings for Forward and Up on the blender exporter, that changes the orientation of the geometry, but not that of the camera's orientation in regards to the scene.
How can I get my camera facing the right way?

To get the right settings for the camera into Fusion7 I found I had to use version 6.1 ASCII of the FBX exporter.

Now my tracked camera and geometry match the blender file :)

Ahem. God helps those who help themselves.

Maybe someone one else will find it useful... Or show me what I'm doing wrong.

Yeah it's totally fine. i just thought it was funny that i'm not the only one who does it http://blender.stackexchange.com/questions/16624/how-do-i-get-constraints-to-work-in-game-engine

@cegaton What version of fusion you use? It would be nice, if you could add this to your answer, because with this we can definitely say: we have to use ASCII 6.1 to make it work for Fusion 6 or 7.


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How come when I render my animation, the audio is clipped when I stitch together the pieces?
I have a slow computer, and I have an animation of 4400 frames. If I render all at once, it would crash. So I made this Python script to try to help me:
#START OF SCRIPT

import bpy
import time

wait = time.sleep
start = 0
end = 4400
increment = 10

current = start

for i in range(start,end + increment,increment):

    wait(2)

    current = i

    bpy.data.scenes["Scene"].frame_start = current + 1
    bpy.data.scenes["Scene"].frame_end = current + increment
    bpy.ops.render.render(animation=True)
#END OF SCRIPT

And I get all of the pieces of the animation:

But when I try to stitch it together like so:

It just doesn't line up. The audio and video are clipped in-between, and the amount of audio frames just doesn't line up with the video.
Did I do something wrong with the script? The stitching? The animation? Please help soon, as I am trying to make this as a Christmas present.
These are the steps I took: https://www.youtube.com/embed/VVY6C2K_1wM
Here is the file: http://www.pasteall.org/blend/33331

If you post links for the first two video clips and also the first two audio clips then people will have something to test with.  You might also want to update your answer with: Step1, Step2, Step3, etc... without skipping anything that you are doing.

@MarcClintDion I added a link to a video.

your explanation was fine without the video.  The problem is that without some of the assets that are causing the problem, a person who wants to look at this issue has to recreate all the assets by guessing at your setup.  This could take all day(or more) and the results will likely not help you because the person was only guessing at where your problem may be.

I added the file.

Don't render out movie strips. Render out images in PNG and add the images as an image strip. Then add the original audio clip afterwards, in the final edit.

I unfortunately can't test for you, but I think rendering one image at a time should be easier on your computer than what you're doing now.

@NaioaiStudios So can I add this ( bpy.ops.sound.mixdown() ) line to the script, change to PNG, and then render?

Don't use the script =) Change output to PNG and let Blender render out all the images for you. Test with 100 frames(images) first. When that's done, you go to video editing and press "Add" -> "Image" and select all 100 images. Blender will then treat this as a movie strip.

Then you add the audio clip, and adjust so the timing matches.

It is good practice to not render out movie strips to a single move file. Instead you should render images as .PNG files and add the images together in the video sequence editor. Then add the original audio clip afterwards, in the final edit. I wouldn't recommend using a script at all.
Change output to PNG:

Set range to 100 frames(to test with):

Then press the normal animation-render button:

When that's done, you go to video editing and press "Add" -> "Image" and select all 100 images.

Blender will then treat this as a movie strip.
Then you add the audio clip, and adjust so the timing matches

It worked. Instead of editing the sound manually, I just did a mixdown for the audio (flac file with all the audio).


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How to lock elbow rotation (forward kinematics)
Before answering this question please consider that an 'answer' involving IK bone constraints should go in comments. In this question I am only interested in forward kinematics.
Many humanoid models use a T-pose like this:

I often end up doing custom rigs, and need to keep them simple (I really do). To avoid unrealistic bending of the elbow while animating, I want to constrain the rotation of the elbow joint.
One method (when using forward kinematics) is switch to Eulers and lock the rotation in UI, as illustrated by this picture:

However, some artists discourage the use of a straight T pose. So we often see this:

My guess is that an axis-angle rotation may do the trick in such cases, however figuring the rotation axis would require tedious calculations; also, behaviour when rotating an axis-angle-locked joint in 3D view is not very satisfying. Finally I don't really want to use something other than quaternion rotations if I can avoid it.
So, what would be a good way to constrain rotation in such cases?

Okay... I also want to ask about the same question with IK. But in such case rotation is locked via the bone panel (or is this method deprecated?) and I believe it would be adequate to file a separate question for this?

Yes this would be better to put into separate question

@Jerryno will the answer be different (testing this with IK now)

You can use bone constraints to limit bones rotations (and other things) in pose mode:
Here is the wiki on rotation limiting.
The settings depend on actual bone setup and what the bone roll values are. Sometimes the bone roll needs to be also adjusted.
This will allow only rotation in local Z axis:

The range of motion can also be adjusted by setting the angle limits for appropriate axises.

Please add some more details on how to actually do it, an answer consisting of just a link isn't really an answer.

I think I tried this before; I don't know how to make it work for a non-straight T-pose. Have you tried?

Actually This seems to work when correctly configured. LimitX, LimitY set to zero or something small, Limit Z unchecked or set to something appropriate (assuming facing orientation on Z axis). Convert should be set to local space and For Transform should be checked. If you can edit your answer with appropriate info, or a screenshot, I will approve this answer.

Sure, I didn't know the actual setting, thanks.


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Break end of cloth mesh into particles in an infinite looping animation
I'm trying to experiment with both Cloth physics and particles, and I need a little help.
I have a character with a long coat, and I'm trying to get the bottom edge of his coat to kind of... break(?) into little bits, like embers or smoke or something; but at the same time, I don't want to break his entire coat.
Cloth physics work OK on the coat itself - it behaves.
Is this possible? Just to 'break' a little bit of his coat while still allowing it to move like clothing?
Tell me if I'm being too vague, and sorry in advance if I am.

You can put a particle system after the cloth one and then use Explode modifier to break the mesh.

If you input a vertex weight map to protect some faces it will randomly break the unprotected ones and create effect like this:

great idea! But how would I go about looping it? (noob question, I know, but I'm curious)

how the loop looks like, the cloth needs to assembled back? like a ping pong animation? you can do this in postprocessing


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scaling a circular shape while keeping its thickness
I have this circular shape:

I need to duplicate it and scale it, in order to have a copy of it, with the same thickness, just with a bigger radius.
Using duplicate and scale (using the 3D cursor as center) the result looks like that:

As you can see the external one is much thicker, because the thickness was scaled as well, is there a simple way to have the second one as thick as the first one?

You should have just one segment arrayed to a curve. That way you could just scale the curve.

Add a curve with desired shape and set its orgin point as shown below. Then add the one segment of the model in the same place where the curve origin point is.
Add the Curve and Array Modifiers to the model segment. Set the proper array count.

Now scaling the curve and increasing the array count, you have a bigger object while keeping its thickness.

Ooops, I just realized that Vince Scalia answered your question before me. All the Kudos should be given to him.


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How to check how much GPU memory is used by object?
I wonder if there is any way to determine how much memory object or group of objects is going to use while rendering.
I was trying to follow some of recent Blender Guru's tutorials but it seems like I have complex object (trees) which even if set alone on separate layer, take too much RAM.
Is there any alternative?

Trying to simplify object?
Is it possible to render part of scene on GPU and part on CPU?

Objects like trees or toothbrushes take up much memory.
For trees, even games use object instancing. While copying the tree, use Alt + D. This will keep you from editing the trees individually but will keep the memory requirement low, you can also have a few trees and create an illusion by rotating them, (fake it!)
Too many leafs will unevitably result in high memory need. I strongly recommend you to take a look to this cycles instancing test.
If you don't want to lower the details, you can try caching the required files on your computer(cycles only). To do this, you need to use the (Cache BVH) checkbox under the "performance" section of render tab.
User preferences also let you to adjuct the available RAM to use.

Thanks! I used linked copy (ALT+D) for trees. The issue I have is that even 1 tree is too much for my GPU. I was wondering if there is a way to check how much RAM will be required by simple object or group. I'll check out Cache BVH and instancing test.


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How to obtain a precise stroke in dynamic topology?
I have seen in this video a workflow that i find very interesting, however I'm having problem getting the dynamic topology part right, starting at 4:25 you can see the author of the video sculpting with very narrow and precise lines, such as those which can be seen in this screen:
However, after copying his brush and detail size (and using basically a sphere with a level 1 subsurf modifier applied as he does) the lines i get are VERY ugly:

Also the polished area on the right doesn't look nearly as smooth.
After messing up with the settings for quite a while I can't find out how to obtain such a nice looking result, I think I am missing something very obvious, being a complete beginner to blender.
So, how can i obtain such precise details when sculpting with dynotopo turned on?

Worth mentioning is that I have the exact same problem when trying to reproduce effects from the exact same video (found at https://www.youtube.com/watch?v=hoaPM1C1vAE .

have the same Problem .
The new Wiki help doesn t exist for that Dynamic topology feature (alt F1) and the other sculping feature are bad explained often in one sentence.
That really not good specially for novice in Blender like me . The older Blender wiki helps are really great tell a lot of thinks and explain it very well The posts here show that tiny adjustments on brush or stroke settings how the locking feature or constant to relative are a big help. I used sculping for producing the shapkeys for animation and its amazing Fun to use. I try now hardsurface sculping and all infos they can h

There are two settings that effect what you are trying to do.
The detail type method in dyntopo effects the way the detail size is calculated. Relative detail uses the onscreen pixel size as set in detail size when creating new edges and will give more detail the closer you zoom into your model. Changing to constant detail will use the same edge size as you zoom in and out. With constant detail the detail size is defined as "a percentage of blender units in object space", which means the objects scale property also plays a part in the size of the new edges.

The other option that will effect this is the brush radius. At the end of the radius slider there is a little padlock, enabling this will provide the same brush size relative to the model as you zoom in and out. The size is determined when you enable the padlock.

You might also want to mention the detail size setting itself.

Good point, @gandalf3.  Your screen resolution can also be a factor since pixels are different sizes on different displays.  I find I have to get to very small pixel sizes to get the effects I see in training videos.  Odd because my display is very high resolution.

The size of the brush in sculpt mode is determined in pixels.
If you change the brush size it will make more detailed sculpting. But the magnification on the viewport is really the key to detail. Zoom in to your object and you'll be able to add however much detail you want.
Here's an example:

Turning on smooth shading would also help.

I know, but to obtain a result as precise as that of the video i have to zoom in a lot, which isn't very practical, while the video's author keeps the whole mesh in sight, without having to zoom a lot. Also, if you look at 4:35 he defines a new brush and even if he is using a huge 45px brush without a lot of zoom he gets very sharp strokes, i copied the brush, but i still get strokes that are very large and imprecise! (he even has flat shading on)

I have the exact same problem.  Drives me crazy.  We need a clear tutorial or document on optimizing sculpt brush settings for Blender.


text:
How can I combine two render layers?
I would like to know which nodes can I combine this two render layers  width?

I've made this with alpha over node and transparent rendering. I want such an image but I don't want to lose the background (Sky texture).

Thanks for helping! :)

The setup using the alphaover node and transparent rendering is a good idea, try going back to that and make the following changes: First go to your Blur renderlayer (in the renderlayer panel) and turn on the Environment pass,

then go to the compositor and add a second alphaover node. Plug the output of the first alphaover node into the bottom input of the second, then plug the Environment pass from the renderlayer into the other image input and pipe the alphaover output to the composite node.

Those screenshots would help future viewers a lot . . .

@NoviceInDisguise Thanks for reminding me, Screenshots added :)

Awesome! Really helps to have some examples like that.

Not sure if this works in your case, but in my case I used a mix node that I have set to "Add".


text:
Render Conversion (Cycles to Blender Render)
BIG EDIT: I have solved this. I just disabled the texture from Cycles and I am manually adding the correct ones.
I have a Blender project I am working on for Christmas, and I had to rig many characters. I rigged them in Cycles Render, but I figured out that if I want a smooth output, I need Blender Render. How do I switch from Cycles Render to Blender Render without deleting the textures? Please respond before the 24th, as I am trying to make this as a Christmas project.
EDIT: This question is different than the thought-to-be duplicate because I am only moving the textures, not nodes. I also tried the accepted answer and it did not solve my problem.

By smooth output do you mean a noiseless render? Rigging isn't connected to which renderer you used so I'm unsure what you mean at the minute.

There is no easy way to switch render engines in blender. Some manual material conversion is required.

You raise the samples, there is also a tutorial here on how to remove them in the compositor: http://cgcookie.com/blender/2012/12/10/compositing-cycles-render-passes-blender/

Read this to see how to use textures in the blender internal render.

When you say that you're only moving the textures, not the nodes, do you mean that you don't use nodes or that you will keep the nodes? If you mean the latter, then you should understand that the material nodes of Cycles are not always compatible with those of Blender Internal, and that Cycles have nodes that don't even exist in Internal.

@MrSquer it would be better if you share your solution in here


text:
Infinite Tunnel Droste effect
I've been looking at videos that create what is called Droste Effect
where an image contains smaller version of the same image and they spiral ifinitely into each other.
like Escher's Print Gallery

or

I've looked at the math behind this here but I don't know I would deform an image recursively to make it repeat itself endlessly,
There are a few videos creating this effect using a tool called Pixel Bender.
https://www.youtube.com/watch?v=CEauXI6fV2A
https://www.youtube.com/watch?v=9WHdyG9mJaI
https://www.youtube.com/watch?v=jrUFx0f_GR0
How can an image be deformed like on the reference the videos to create an infinite tunnel in blender?

That is messing with my eyes in so many ways.

Related: http://blender.stackexchange.com/q/12373/599

You would like mandelbulber

Am I the only one who read "Pixel Blender" instead of "Pixel Bender"? :P

@gandalf3 no, I had to read it several times.

here is a messy node setup that  could be turned into one  python node "I'll try to do that " :
this is the node setup

this is the node-group

the object index in the node-group should be that of the "object of interest", also the is object is unwrapped before.

finally here is a quick simple render :

*the UV and ID outputs of the node group are only added to ease hooking up more nodes sequentially

Very nice! Now I need to figure out the distortion so the images blend within themselves as in the kid holding the frame... any ideas?

What version of Blender are you using?

@PGmath 2.73 why?

@cegaton I meant Chebhou, there are five types of nodes to use (at the bottom, to the left of "use nodes").  I am used to three: material, compositing, texture; and I am wondering what the other two are.  I am using 2.73RC and I only have the three.

the first one is for the " animation nodes" Add-on , and the last one is for the "SVERCHOK" Add-on  which is parametric geometry creation node system. They are both very interesting and useful


text:
How to import a Wavefront .OBJ with Blender 2.73's bpy API?
Can someone direct me to the equivalent of the earlier import_scene operators - like bpy.ops.import_scene.obj() - in Blender 2.73?

I don't know of any import/export related changes that have been made for some time.
The bpy.ops.import_scene.obj() operator will only be available if the Wavefront OBJ addon is enabled, check that it is enabled in User Preferences.


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Add animation to armature which is already animated
I imported a armature from Daz3d to Blender. This armature has an animation. Next I added another armature into Blender. Can I add the animation from the first armature to second armature?

Most animation data recorded in blender gets saved as an action, an action can easily be applied to another object, it will work fine as long as the animated data path names match in both objects. For an armature that means an action created with one armature can be applied to another armature and it will move bones that have the same name as the first armature.
For non-matching armatures not all is lost, but could be more work than it's worth. You can add constraints to have a bone follow the motion of another bone. If your animation is simple it may be easier to just animate the new armature, you can use the original as a reference to make it easier.


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Can I have two different UV unwrappings of the same object?
Basically, I have two textures, one of which is mostly transparent. I want to combine them, so that they're one on top of the other.
The problem is that one is bigger than the other, so I would need two different UV unwrappings of the same object, one with a bigger scale than the other.
Is it possible to do so or should I combine the textures in an external program?

Yes, this is possible. Combining textures is not a bad idea either.

Yes, it is possible.
In the mesh panel, under UV Maps, press the "+" button. This will create a new UV map with the same coordinates as the existing one.
For Cycles, in the node editor, select Input -> UV Map to use different UV maps for different shader parts.
In Blender Internal, you can select which UV map to use in the texture panels.

That was quick! And it worked perfectly, I'll accept the answer as soon as I'm allowed to!

Yes
Just go to the object data panel of the properties view (where you go to modify vertex groups) and click the little "+" under  the UV maps rollout to add a UV map.  Then when you go to UV unwrap a model just select the UV map you want to modify.


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Does one scene affect other scenes?
I have 2 scenes in my blend file, one for texturing and rigging, one for the actual animating and rendering. Does the rigging scene affect the animating scene?

It depends, scenes can be linked, and they can be unlinked

Each scene in a blender file is separated from each other, using it's own settings.
The data in a blend file can however be shared between scenes, this may be an object, mesh data, material etc. For example when you selecting a material, every material in the file will be listed and show up the same in every scene. When you use the same data block in multiple scenes then changing the item in one scene will also change it in other scenes.
The easiest way to tell if an item is unique is by the name, data blocks linked between scenes will have identical names. Here you can see that Suzanne is the same object linked between scenes, while Suzanne.001 is a different object that is only in scene.003.

If you want to use the same object in multiple scenes select it and press CtrlL and under Objects to Scene choose which scene you wish to link it to.

So the answer to your question will depend on how your file is setup, this should help you find out and to setup your file as you want.


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How do I make a material with transparency have a foggy illusion?
I have a material for all glass in my scene, and it is transparent. Can I add "fog" to the material to give the illusion that it is cold out? This scene is in Blender Render.

Have you tried volumetrics?

try this tutorial


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How do I delete a Grease Pencil ruler?
In the grease pencil menu there is an option for adding rulers and protractors.
Now, as far I understand, I can remove all rulers by pressing ESC but if I press ENTER instead rulers get saved.
In various places (prominently, in a kind of help line while in ruler/protractor mode) it is said that pressing DEL will delete rulers, but I cannot get it to work.
(tried in Blender 2.71).
Is it a bug, an error in the docs, or am I misunderstanding the context of this operation (e.g., how would I select a ruler so that I can delete it?)

Pressing Delete will delete the active ruler (whichever is selected or left-click to select a specific one) before having pressed enter (all the options in the help line are options for during the creation of the ruler).
If you have already pressed Enter you can re-click the grease pencil 'Ruler/Protractor' button to re-enable the rulers and go through the selection and delete process described above.
After pressing Enter the rulers are saved to a grease pencil layer, so you could delete all rulers at once via the grease pencil panel in the properties menu (N) in the 3D view by selecting the grease pencil layer in the list and then pressing the ' - ' (minus) button:

This provides a way to delete all rulers, which is very good (tested). But, if I create a ruler, then press DEL right away, it doesn't get deleted either (now tested in 2.73). I might ask another question elsewhere (how to select a ruler?) but I would assume that there is a way to delete rulers individually, even after pressing ENTER? Since reactivating ruler/protractor mode allows editing existing rulers? Up-voting but for now still thinking this answer needs clarification.

I have added more information regarding, selecting rulers and deleting rulers individually. As for the Del key, that works for me. If you are finding it doesn't work please make sure you are using the latest version of blender (2.73a) and test again. If it still doesn't work (baring in mind it definitely does for me) then you may need to submit a bug report to https://developer.blender.org/

I got a hunch and found that, on some Apple hardware (e.g. Macbook Air), backspace and delete are merged into a physical key labeled "delete" - defaulting to backspace. So, in order to delete rulers in this case, pressing fn+delete is needed. While the answer and the docs are accurate, it would be gracious to include this clarification in your answer.


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Rescaling a baked F-curve to values between 0 and 1
I'm trying to drive a shape key by baking an audio file to an F-curve. However, although the audio is normalized to -.1 dB, the peaks of the baked curve are far too low, and never even get close to 1. I need to highest peak to give the shape key a value of exactly 1, and the lowest to give the shape key a value of exactly 0, so I need to scale the F-curve and possibly also move it up or down a bit. To do this, I need to find the maximum and minimum values of the baked F-curve. How can I achieve this?

did you try the Envelope or Limit modifiers

@Chebhou The problem is that baked F-curves can't be edited, so I'll need to use the F-curve for a custom property and use that as input for a driver for the shape key. I did try the bake action as per my own suggestion in a comment to this question, but that only bakes the location, rotation and scale.

if this solve your problem write an answer F-Curve Amplification

@Chebhou I couldn't get that to work. The speaker tools don't show up in the addons, although it's installed. However, I tried resampling the audio to 32 bit float, and suddenly the height of the baked curve was a lot more to my liking, and possibly with some edits, eg compressions and/or normalizations, I may get what I'm after. It looks like Blender doesn't map unsigned 16 bit integers correctly. Perhaps I should file a bug report about that. I'll do some further experimenting, and if I'm able to get close enough, I'll post it as an answer.

That should be signed 16-bit integers. This is the most commonly used format for .wav and .mp3.

@Chebhou that link looks familiar.

@batFINGER I don't get what you mean

@Chebhou  link above 'F-Curve Amplification'  old one of mine from BA nevermind... not important.  SixthOfFour, PM me on BA if you are interested in getting sound drivers to work.as I've not had a problem with remapping 16bit audio.

@batFINGER Thanks. At present this isn't the top priority for me. I'm having some private issues, due to which I don't have as much time and energy as I'd like to play with Blender. I may take you up on that offer later though, provided it's still open then.

I've partially solved this by using some external programs.
First I edited the audio in Audacity, to get a curve shape I was happy with. I won't go in to the detailed workflow, as this would be beyond the scope of this site. What I did was basically applying a series of compression, normalization and amplification filters.
Secondly I resampled the audio to 32-bit floating point, as it seems Blender doesn't correctly map 16-bit integers to values between 0 and 1. For this I used SoX.
sox <infile> -b 32 -e floating-point <outfile>
(I could do both with either program, but I find SoX to be better at resampling and Audacity more intuitive, as I can see the changes directly affecting the shape of the curve).
Then, in Blender, I created an object (in this case an icosphere) and added a keyframe (in this case to the Z location) at frame 1.
Then, in the graph editor, Key > Bake Sound to F-curves

Experiment with the different settings. I used an attack time of 0 and left the others to their defaults. Increasing the attack time may make the curve smoother, but it may also introduce clipping below 1.0, if the curve starts decaying before the attack time has passed. Likewise the release time may introduce clipping above 0.0, if the curve turns upwards before the release time has passed.
Here's what I got

The animation gets a bit jumpy. This is mainly caused by resampling the audio to the framerate (e.g. resampling from 44100 samples/second from a CD source to 25 samples/second for a PAL DVD).

I'm afraid that the accepted answer to this question, while feasible, is a long and hard-to-tweak workaround. Also, a similar (later) question has a good answer here. To summarize what's there, and what I've read elsewhere, there are three options:

Create a custom property, bake your sound to the property, then create a driver with a simple python expression to drive other properties at the required scale. This is what I did. More details in the link above.
Use the Sound Drivers add-on. (I haven't tried it, but it looks nice!)
After baking, un-bake the sound to a normal F-Curve. Then you can scale it or edit details.

Good luck!!! :)


text:
Viewport render info from Python
I'm writing a script to overcome some of Cycles' limitations in terms of performance, namely the loading time, which is very long in the case of heavy scenes.
I wrote a modal operator which, at the moment, creates a timer, toggles the current space fullscreen, and takes a screenshot at fixed intervals; since the viewport rendering does not reload the scene at each frame, part of the BVH building time, shaders update and device loading are done only once. I will of course use the real rendering for the final render, but this may prove useful for quickly rendering previews of a WIP.
What I'd like is to check for some values in the viewport, eg. samples rendered, rendering state (updating mesh, loading BVH, path tracing, etc.), in the same way as it is displayed at the top of the 3D View. This way I can check the current state and take the screenshot and set the next frame accordingly (eg. (pseudo-code) if samples_rendered > threshold: take_screenshot() and set_frame(current_frame+1). This wouldn't rely on an arbitrary timer, which doesn't account for the initial loading time, nor the time variations in rendering the frames.
Is there a way to access this information in Python?

The viewport uses a different BVH structure which allows for individual objects to be dynamically updated without re-updating the whole scene, however it results in slower sampling speed. Not sure if using this method would actually end up being faster for final renders or not (where there are typically more samples), but it would be interesting to see some tests.. AFAIK You can't set the final render to use dynamic BVH without editing the source code, but you can set the viewport render to use static BVH (the kind the final render uses). Perhaps useful for testing.

Well, for light scenes I'm quite sure it wouldn't add any benefits, but the one I'm working on is really heavy, and since I don't need render passes, full sample count, motion blur, etc for preview purposes, it would definitely be faster in the viewport.

The status as seen in the info area is set by native code, it can't be accessed with Python AFAIK. But you might want to look into app handlers, there's a callback right before and after a frame has been rendered - not sure if cycles supports it however.

Cycles does support render handlers, but unfortunately they don't seem to work for viewport rendering, so I can't use them here.


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How to create an array of lamps?
Following this question.
Since you can't use an array modifier on lamps, how can you create an array so that all lights are clones of the same original and can be edited as one?

Start with a plane that has the proportions of your lamp, enter edit mode and do loop cuts CtrlR so you end up with as many vertices as you need lights.

Set instancing to Verts.

(for versions 2.79 or older) Set the duplication to Verts.

Add a spot lamp on the same place as your plane.

Select your lamp, then shift-select your plane and press CtrlP and select Parent to Vertex

You have now an array of lights!

To have the array follow your plane's rotation select the lamp and add a copy rotation constraint.

Note that the object doesn't necessarily have to be a plane, it can be any shape you want and it doesn't even need to have faces, as the lamps are controlled by vertices.

and adding/removing vertices gives control on the number of lamps. Easy scaling/spacing...Very nice! Can be subsurfed! :) (for test/final render)

i was able to change the plane to a set of 3 vertices on a single line (no longer a plane technically), then added modifiers to the plane to create an array of sets of lights that i used to illuminate a bank of warehouses.

@neoscribe indeed you don't need a regular polygon, since you are just using the vertices to attach lamps to it.

Valid for 3.1.
Lights must be anchored to an object, but you can use an array as well to create the anchors. The advantage is you can manage light locations and number using the array modifier parameters.
(With recent versions of Blender it's also possible to use geometry nodes to instance lights on vertices as explained in this Q/A.)

As the most simple anchor is a vertex, just create a mesh with a single vertex, then apply a modifier to create the array:

In the example above two arrays are used to create a grid of single vertex objects.
Then follow the process already explained in the currently selected answer, i.e.:

The distance between light origin and object origin will determine an offset for instances we're going to create. This offset is usually not desired, so move the light to the single vertex object location.

Parent the light to the object by last selecting the object (parent). Reminder for parenting: In object mode,  Use Object | Parent | Object (shortcut Ctrl p). You can also drag-drop the light object onto the parent in the Outliner:

In the object, switch Instancing from None to Vertices. The child light is now instanced for each vertex of the parent (here only one vertex), and because the light is now part of the vertex, array modifiers duplicate it as well:


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Texture painting, zoom pan causes texture to get an offset
Hi I have a problem when texture painting on a huge plane.
Whenever I zoom or pan my view (even just pan without zooming) and paint on a location I painted before, the texture gets an offset and of course does not fit anymore to the rest I painted.

You can use stencil for the brush mapping. This gives you a semi-transparent overlay of the texture that you can position before painting.

You can use  RMB to move the texture ⎈ Ctrl  RMB to rotate it and ⇧ Shift  RMB to scale it


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First Person Camera In Blender Game Engine
I am making a game in Blender with a first person camera. I used a mouselook script I found online, however when character motion is used for the camera's movement, I have the problem that when the character is looking at the ground and presses the S key, they move up. I am writing a script that will detect when the mouse moves up and down, and another that detects moving left to right.
Where would I start? I was looking at the documentation, and I found bge.types.SCA_PythonMouse.position, but that does not tell you when the mouse is moved. Is
there a function that does this?

Probably off-topic, but I think you're after mouse events, which Blender does appear to have.

no need for a script to get mouse movements use the logic bricks :