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Strange anisotropic artifacts?
I am setting up an aluminum material using Blender's internal renderer. It gives me a strange output. I attached 2 screenshots below, one is the render output and the other is the texture settings to achieve the anisotropic effect.

The following image is the texture settings.

If I do an edge subdivision at the spot where the anisotropic effect looks wonky, the wonkiness shifts upwards. What did I do wrong? How should I fix this issue?
EDIT
Following @CharlesL ' s comment, I attached a screenshot showing all normals are pointing outside.

EDIT
This is the .BLEND file for your analysis.

Have you tried recalculating your normals? Enter edit mode then press Ctrl-N.

Yes, I've done that. It is still the same. I've just attached a screenshot in my question above.

Would you like to upload the file for easy analysis?

@LeonCheung it is added now.

Tangent shading for BI was introduced in 2.42. According to the feature note:

Using the 'tangent' option in the Material → Shaders panel alters the direction of shading to use the tangent vectors, giving anisotropic shading for any of Blender's diffuse and specular shaders. This is useful for creating brushed metal or wood, where the microscopic grooves in the material give highlights that follow a direction, rather than just being circular.
Currently, Blender uses a mesh's UV co-ordinates to define the direction of the shading (along the V axis). This means that models must be UV unwrapped to take advantage of tangent shading.

So, an expected anisotropic result needs UV coordinates to know which direction the light should stretch. To be exact, the anisotropy will stretch the light vertically along the UV coordinates.

For the attached case, You can unwrap it from the side view with UV unwrap methods like Cylinder projection, which is usually recommended. Besides, using UV as the Coordinate type in Texture setting is the better choice as well.

You should UV-unwrap your model. I suggest to apply a
cylinder projection from the front ortographic view.
The UV also controls the anisotrophic direction.
Otherwise the tangent is calculated based on the normals.
Where te interpolation of the face normals is near to z = 0
the tangent calculation gets numerically instable and I think
the tangent also gets negated there. At least it seam so, but
I am not sure how Blender calculates tangents based on normals.

I would strongly suggest you use cycles for this, because there that sort of issue isn't a problem.
Afaik this error could be caused by lighting.
I forgot how the effect is called, but if you have too few light sources in "old" raytracing, you can end up with quads "split", meaning one tri gets light only from one light source, the other only from the second lamp, and you can see a "seam". Have you tried adding a hemi to your scene?


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Moving an f-curve from an object to a bone
I'm altering some animations from direct animations on the object to animations on the bone that influences the object.
I've appended the action to the .blend from the original .blend and applied it to the armature. However, I want the f-curves in the action to apply to one of the bones in the armature, not the armature itself. The only way I've found to move the data is to insert keyframes on the bone then copy the keyframes in the graph editor.

Yes you can. The workflow would be:

Append the action;
Switch to Dope Sheet Editor (shortcut is ShiftF12), then change Editor Mode to Action Editor;
Select the appended action from the dropdown list in the header, select keys you want, then CtrlC (or click the second last button at the right-end of the header);
Select the target bone in Pose Mode, add necessary channels by keying if there isn't any yet. Make sure the cursor is at the expected position, select channels you want to add action on, then CtrlV to paste (or click the last button at the right-end of the header). You can also do this step in Graph Editor.

PS:

The action can be transformed between objects and bones, as long as they got same channel types. However, the result may be not always as expected as you really want.
One thing that you should be aware of is the consistency of the rotation mode. For example, if the action for the appended action uses rotation mode as XYZ Euler, and the bone uses Quaternion (WXYZ), then it will fail, either.

I found to select the keyframes, I had to press "L" to select the all of them for the channel.

@BenJaguarMarshall That's right. It will speed it up a lot while doing so. Congrats, you got the trick. ;)

source: Stack Exchange

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

sort: votes


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Unwrap Separate Meshes
I have so many books models to texture. Texturing them one by one will be a pain. Can Blender unwrap two (or more) separate meshes and make them share the same UV grid?

Note that if your objects are the same you can unwrap one and then copy it's UV map to the other objects with Ctrl+L > Transfer UV layouts

Possible duplicate of Combining UV maps.

As long as all the vertices in your objects are completely connected to each other (no loose parts) the following technique will work:

Select all your objects, and press CtrlJ. This will join them into one  mesh.
Press U > Unwrap (or whatever unwrapping method you want use).
Press P > Separate by Loose Parts.

This works great for quick 'n' dirty unwrapping onto a tileable image, but it may make more sense to link them all (like Matt said). The simplest way to link them early in a project is to duplicate them with AltD instead of ShiftD. It will link the mesh and the UV map which will make things easier later on.

(Warning, this method might undo some work, so save before you try it)
Not precisely, no. But you can make all the models use the same mesh, IWC they would also use the same UV maps, and you'd only have to unwrap one of them. If they are all sufficiently similar, you can select all of the books and press ctrlL, then select "Object data." This will make all of the objects use a copy of exactly the same mesh (in fact, if you tab into edit mode for one of them, all the other linked meshes will also be highlighted as if they are also in edit mode). This way, you can edit the mesh (or UV map) for one, and the others will all use a copy of that.
Incidentally, if you want variation in the books, you can still move, rotate, and scale the OBJECTS independently. I.e. you can make one book fatter than the others by scaling the object on one axis, without changing the mesh.
Furthermore, you can make any or all of them unique individuals (no longer using copies of the same mesh, but rather each using their own mesh) without losing the UV map. Click the number next to the name of the mesh to "Make single-user copy." Then that one will be identical, but independent. You'd have to do this for each one, which might be tedious, but that only matters if you want them to be independent, like that.
Good luck!

authors: Вячеслав Пискунов

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


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How can I analyze whether my camera is looking up/down?
The question is exactly the same as the title: How can I analyze whether my camera is looking up/down? :)
A bit of explanation: I am writing a script that handles both 3rd and 1st person view, and now got stuck at the point where I want setting a cap to prevent the view from turning around vertically.
For this I made an "if... elif... elif..." statement.
The first branch tests, whether the sight is between the caps, and if so, then lets the user move the view.
So after that, I need to check which direction the user wants to move the view, plus which direction is it stuck to. These do for the 2 other branches.
So this is why I'd need your help.
Awaiting your answers :)

When the camera's X rotation (in euler rotation) is at 90 degrees it is looking parallel to the ground. Less than 90 it will be pointing down at the ground, greater than 90 is pointing up.
if camera.rotation_euler.x > 90 and camera.rotation_euler.x < 180:
    # looking up
elif camera.rotation_euler.x < 90 and camera.rotation_euler.x > 0:
    # looking down

This simply stops my script from working. :(

BTW, am using Blender 2.69

If you just copy and pasted then you will also need to add something like camera = bge.logic.getCurrentScene().active_camera so it knows what object camera is meant to be referring to.

scene = bge.logic.getCurrentScene()
...
empty = scene.objects["empty"]
->this is what I want to rotate, so this is not the problem

Note, using rotation_euler is incorrect, it wont take constraints or parenting into account. use matrix_world.to_euler() instead if you need the worldspace euler.

It says, it doesn't know matrix_world and rotation_euler :(
Maybe they have a different name in blender 2.69?

hmm, is it possible it doesn't work in the game engine?

@user1733 - the question does not mention the game engine.

This simple script gets the angle from the up axis to the cameras view-axis.
import bpy
from mathutils import Vector

camera = bpy.data.objects["Camera"]
z_up = Vector((0.0, 0.0, 1.0))
z_camera  = z_up * camera.matrix_world.to_3x3()
angle = z_camera.angle(z_up)

is_up = angle < math.degrees(90.0)

Note that matrix_world and not rotation_euler, this is important since rotation_euler is the rotation input from fcurves and drivers, and not the final transformation of the object with constraints and parents.

erm, where does "z_camera" come from?

@user1733 oops - corrected.

Got it! :)
#_CAPPED STATUS:
aroundX = logic.getCurrentController().owner.worldOrientation.to_euler().x      #_getting rotation direction: + on Up & - on Down
capped = False                                                                  #_capped is "False" as default
if (aroundX > 1.3 and y > 0) or (aroundX < -1.1 and y < 0) == True:     #_capped becomes "True" when  it has to
    capped = True

y shows the mouse movement's 2nd coordinate

I have another idea, you could calculate the angle between the z-axis which points upward and convert the camera rotation to a transformation matrix to create another vector pointing to the camera. After that you can determine the angle of the camera to the z-axis with the dot product which returns the cosine of the angle. @samblers suggestion doesn't seem to take rotations on the cameres y and z-axis into account.
With this method you could limit (if..else) the angle from 0..70 (max 90)
import bpy
import math
from mathutils import Vector

camera = bpy.data.objects["Camera"]
origin_z = Vector((0,0,1))
cam_rot  = camera.rotation_euler.to_matrix().to_4x4()
z_cam  = origin_z * cam_rot
angle = math.degrees(math.acos( origin_z.dot( z_cam )))
print( angle )

I verified this with the Math Vis addon enabled:

You might find this a great tool when coping with rotations and vectors. Simply enter
origin_z = Vector((0,0,1))
cam_rot  = camera.rotation_euler.to_matrix().to_4x4()

into the console and see how it looks like.
Some examples:

Prints 0.0

Prints 39.00000357556496

Prints 39.00001985547789

Prints 53.46396688981824

Thanks for the idea, but I just cannot find any way to implement it into my script to get any use of it. :(
BTW, does it give back numbers like °s? or radians? or something else?

It prints degrees 'angle = math.degrees' if you need radians simply omit 'math.degrees' in the last line.

How about adding your script to the question?

coming in parts: (but this is a reworked type):
import bge;
from bge import render;
import mathutils;
scene = bge.logic.getCurrentScene();
def main():;
#_LOOK PROPERTIES:;
rotSpeedX = 0.005 ;         #_setting mouse movement speed (right & left);
rotSpeedY = 0.005 ;         #_setting mouse movement speed (up & down);
cap = 82.00 ;              #_setting rotation cap (up-/downwards);

#_SENSOR AND OBJECTS:;
mouse = bge.logic.getCurrentController().sensors["mouse"];   #_sensor;
ketrec = scene.objects["ketrec"] ;                           #_object;
empty = scene.objects["empty"] ;                             #_object;
karakter = scene.objects["karakter3rdP"]  ;                  #_object;
#_MOUSE MOVE PROPERTIES:;

x = (render.getWindowWidth() / 2 - mouse.position[0])       #_getting mouse move;
y = (render.getWindowHeight() / 2 - mouse.position[1]);      #_getting mouse move; vector1 = mathutils.Vector([0.0, 0.0, 1.0]); camOri = empty.localOrientation

ector2 = mathutils.Vector([camOri[0][2], camOri[1][2], camOri[2][2]]); inRad = mathutils.Vector.angle(vector1, vector2); angle = inRad * (cap / 3.14); if not mouse.positive:; #_BUG FIX: ( MacOs )#; x = 0; y = 0;;;
#_CAPPED STATUS:; capped = False; if (angle > (cap / 2) and y > 0) or (angle < ( (-1) * cap / 2) and y < 0) == True:; capped = True; #_APPLYING ROTATION:; ketrec.applyRotation((0 , 0, int(x) * rotSpeedX), False); if not capped:; empty.applyRotation((int(y) * rotSpeedY, 0, 0), True);

#_RESET MOUSE POSITION:; render.setMousePosition(int(render.getWindowWidth() / 2), int(render.getWindowHeight() / 2)); main()
Sorry, but this was how I could insert it :(

@user1733 I meant editing you question with 'adding the script'. I tried to assemble this but couldn't find out where the line breaks should be.

at the ";" marks
thanks for the help btw everyone


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Export 3DS file with pivot point in Blender
Hi I've been working with Blender for some time and I can't figure out how to export 3DS with pivot point. I tried exporting 3DS by putting 3D cursor and the object origin, but it doesn't seem to export the pivot point either. Need help on this.

3DS file exported from Blender does keep pivot point data, you can confirm this by importing it back into blender, with Apply Transform toggled. I think you should look into more settings of that application when you are going to import into it.


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Can I make Blender a Y-Up world?
After using other 3D Apps I have become used to Y being up, and Z being depth (Depth pass, Z pass etc).
Is there a way to make Blender a Y-up world, and if not, does anyone know why they chose to be different ?

Duplicate Question. See: Is it possible to make Blender a Y-up world?
"The standard orientation, where the xy-plane is horizontal and the z-axis points up" is part of the Right Handed Orientation coordinate system. It is not "being different" as much a choice between Left or Right Handed systems. Each design team makes there own choices when they first start coding.

This is incorrect, the handedness of a coordinate system refers to which direction the z-axis points relative to the x and y axes and is separate from which axis is up. For example the conventional coordinate system for CAD applications is right-handed with z up while the one for VFX and animation software is right-handed with y up.


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Cleanly Combine Two Landscapes
I used the landscape generator to create two mountain ranges.. They go edge to edge and have a weird clipping effect. I want to join them together and have the vertices joined cleanly and look normal. How could I go about this?

You can combine two landscape using the bridge tool.

Select one of the landscape in object mode and move it away from the other slightly.

Select both landscapes in object mode
Join the two object together, Ctrl J

In edit mode select both edge loops between the landscapes.

bridge them together using the bridge tool, W -> Bridge Edge Loops

Number of Cuts: adjust this so that the generated polygons look square
Interpolation: Blend Surface, has the best look for bridging terrain
Smoothness: adjust this to your liking

Final Result

Best answer so far. Exactly what I was looking for.

Using a heightmap (first method I thought of)
Assign a gradient to both of them, from black to white along the z-axis. Render this from the top to get the combined heightmap. See this question:
Displacement map from existing 3d geometry
Create a new plane and assign the rendered heightmap.
Using the shrinkwrap modifier (second and better method)
This is fairly quick, easy and gives excellent topology.

Join the two planes into one object.
Create a new plane with desired resolution. Place it over the two first.
Make it the same size in X-Y direction.
Add a shrinkwrap modifier to the new plane. Set the target to the joined terrain object.
Set mode to Project.
Make sure Negative direction is ticked.
Select Z direction.

Result:

I recommend to use Boolean modifier:

Select one Landscape object, enter Edit Mode, ShiftCtrlAltM to select non-manifold edges; E to extrude selection; CtrlF > Grid Fill;
Repeat Step 1 for the other landscape object; Add Boolean Modifier on either one, set Operation to Interset, set Object to another;
Apply the modifier; Enter Edit Mode, press X to delete the selection (supposing you didn't change element selection in Step 1 and 2).

NOTE:

You may also want to remove doubles or recalculate normals by then.
Boolean in blender needs objects being solid. That's why we need to do like this.


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Method to align object local axis with global plane when rotating on local axis?

For the cube shown I want to do a rotation on the cubes local z axis so that the cubes local x axis lies on the global xz plane.

Try to apply rotation on the cube (CTRL+A)

Thanks for your answer Leon. I found a way to get the desired rotation using a LockedTrack constraint. The trick is to target an object that is 90 degrees to the plane you want to align to. Then apply visual transform.

Select the cube, Shift S > Cursor to Selected, choose 3D Cursor as current pivot point, or simply press . (the period key).
Press Numpad 1, add a plane object, press F6 then toggle Align to View, in order to make it parallel to global XZ plane.
Select the cube, then View > Align View > Align View to Active > Top (or simply press Shift Numpad 7), then add another plane object, toggle Align to View in F6 panel, as well.
Keep current View unchanged, add an empty object, toggle Align to View in F6 panel, as well. G X X to move a certain distance along its local X axis.
Add a Boolean modifier to either one of the plane, set Boolean mode to Intersect, choose another plane as the target object, in order to generate the intersection line from two planes.
Enable Snap icon on 3D View header, choose Edge as snap element, and Active as snap target, first select the cube, then select the empty by holding Shift to make it active, R Z Z, move mouse over the intersection line generated in Step 3, until it is snapped, LMB or Enter to confirm. Finally, delete these extra objects.

This is the non-coding way I've ever found so far, which is not hard, just need a bit more operations. I'll try make a GIF if necessary.


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How to connect faces without intersection?
I don't want to change the geometry of the faces I want to connect to. I'm sure more seasoned 3D modellers have a simple way for this. Please enlighten!
In the tutorials for joining cup handles to the cup they line up so it's not an issue. Another tutorial even extruded the start and end of the handle and then joined them in the middle. I don't think either would work here.
Here is the cross section:

Do you mean you want to avoid face intersection?

You can use Boolean modifier to join them together. If the handle is in the same mesh of the cup body, just simply separate it as a new object by P, then boolean the two object. You will get a final shape without intersection after apply it.

NOTE: When using Boolean modifier, the intersection part has to be closed shape.

I get "Cannot execute boolean operation" -- no further information about the error is presented.

I think this may have what you meant by your note... but I had to add closing faces to both objects (where they were intersecting). @Leon Thank you

@jacobsd Hi, yep, that's the most common error message when experiencing with Boolean. I think you needn't add addtional face in your case. When separating, just don't miss this face.

I got it. I just have to clean up the mesh. Thanks again.

Set another vertex in the middle of the lower edge of the right strip (use knifetool [k] for example) and also add maybe a ring cut [CRTL]-[r] to the other part than join the vertecies with the corresponding ones of the other part of the mesh [Alt]-[m].

How do I create the cuts exactly where the intersection happens? In other tools they might be called "pathfinding". If that helps. I don't mind some geometry clean up -- but I don't want to modify the geometry of the receiving faces.

I would use snapping, also you can slide the place where the cut happend aftewards. May I ask what is your reason for the "not wanting to modify"? A loopcut would go cleanly through the whole mesh, not leaving much traces.

I meant I didn't want to alter the receiving faces' angles. I don't care if I end up with more faces (as I expect that to be a requirement.) I don't want to have to "eyeball" the resulting geometry.


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Breaking a cylinder into sections in blender
I need to know how to cut a shape up into separate sections, for example, how can I cut a cylinder in half, so that I can animate the different sections pivot points, thus the cylinder opens out.
With a cube before I've been able to just duplicate it 7 times, however with a cylinder I need it split in half and into other smaller sections.

Also I don't want a hollow shape i need all sides for materials

There are several ways to do so. As you mentioned, if you really need to fill sections after cutting, I would suggest a tricky way:

Create a mesh that contains expected sections. Add Solidify modifier to this mesh, set Thickness to 0.00001. You can leave other options as default;
Add Boolean modifier to cylinder, set Operation to Difference, and Object to the section mesh. Then press Apply;
Delete the section mesh, Tab into cylinder object, select all elements, P>By loose parts to separate each sections apart;
If you want to recalculate their origins, just ShiftCtrlAltC > Origin to Geometry.

P.S.:
In the latest version (the coming 2.70), Boolean modifier supports ngons, which will generate better and cleaner result.


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Turning my own character into animation
I'm a completely new blender user! I want to change my own drawing (on paper) into animation using blender. Is it possible? and if yes how should i start?

You need to model, rig and animate the model.

Well how should i start?

This might get you started

its definitely possible.

you've got to model your drawing.

how to model

When I start creating a character, I draw it on a paper how its supposed to look from the front, then how its supposed to look from the side.
Then you put your drawing as a background image in blender and model the mesh along the lines of your drawing.

give it an armature, that armature acts as the skeleton of your model and you can animate the bones of that armature.


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Cloth Physics hung on pole?
I am trying to render a physics cloth of a flag. But I don't want to pin it to two points/an edge... I  want it to be wrapped around the pole. In reference to the image I have uploaded: The fabric is to be folded over near one side and stitched to itself about 2" in along the edge and one top edge. This would allow a dowel to fit into the "sleeve". How can I do this in blender so that I can render it on a pole? I tried to but it doesn't work properly.
I made the dowel an AddPassive in Rigid Body Tools and the flag a Cloth in Physics. They don't intersect.
I also would like to know how I can better make the sleeve rather than making a tube.
Thanks!

I would use collision instead of rigid body for the dowel.

Is the sleeve open on the bottom?  I would also recommend deleting the top face of the sleeve, selecting the edge loop around where it was, and doing a grid fill.  To do a grid fill hit [space] and type “grid fill”, you can then hit [F6] and adjust the rotation to get nice even quads.

The sleeve is open on the bottom.

I tried using collision and it still explodes into itself

I don't think subdivision and self-collision matters much, even the model size (just don't make them extremely tiny). In fact, subdivision generates even worse artifacts in some cases.
For the "exploding" issue, what matters much is the Distance parameter in Cloth Collision panel for cloth object, and the Outer parameter in Collision panel for the collision object. When the initial gap between the two objects are relatively small, you need to tweak these two parameters specifically so that they will not become "procedually intersecting" before running simulation.
Of course, subdivision will lead to much better result, as long as key parameters like above can be taken good care of. But it doesn't mean other things are trivial. For example, don't forget to apply Scale for object when doing so.

Example File

You need more subdivisions on the part that goes over the pole. add a subdivide modifier or give more in edit mode.

I've determined that the reason my model is "exploding" is because of the Cloth self collision. When I turn it off it works properly. But I need the cloth self collision on. What do I do?

Have you added more subdivisions?

Yes, many subdivisions and with different designs

@Peter The cloth simulator cannot deal with small models very well, try scaling the objects much larger.


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Custom nonlinear distortion lens
Is it possible to create a custom nonlinear distortion lens in Blender?
I'm assuming that Blender superimposes a rectangular grid in front of the eye, and fires out a ray through the center of each cell on the grid, returning the colour for that pixel.

So my question reduces to: is it possible to replace this grid with my own warped grid?
EDIT: I'm most interested in a code-level solution -- this is for experimental project and as such I would like fine-grained control.
PS I can't find any tags, such as ray-tracing, eye-ray, lens, distortion

You may want to try this patch.

Why not use the compositor to achieve this affect?
Doing this in the compositor is really easy. All you need to do is to add a lens distortion node.

I thought cycles did support fish-eye lenses?

@gandalf3 I see no option for it?

There is a fish-eye option in Camera > Panoramic > Type.

oops you are right

But what if you want the camera to use the same lens distortion values (k1, k2, and k3) that camera tracking determines?

If you want to work at the code level -

You can use a custom blender code base by adding your own node that does what you want. Complicated but will give you access to the most data and the most flexibility that is available in the render engine.
Pynodes allows you to create your own nodes, I'm not sure what capabilities these offer. There is a custom nodes example in templates. I believe luxrender uses pynodes to add nodes specific to luxrender.
Create an OSL shader. The limitation would be the object with the osl shader so you probably won't get the full image distortion that you want.


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Only show colour and NOT transparency?
I have a hair texture , and i took away the white background , but the white hasn't gone away yet!? I want it so all the white is gone and it only shows the colours on the texture .

![Added][3]

possible duplicate of How can I setup a Material in Cycles for Z-Transparency?

There are generally four steps to make sure the viewport alpha display:

Set Transparency Alpha value to 0.000 in Material setting;
Toggle Alpha influence in Texture setting;
Switch to GLSL shading mode in 3D View Property panel;
Use Texture as viewport shading type.

Besides, make sure Using Alpha is toggled in Texture panel, although it's set as default. And you may want to use UV as the coordinate type of texture mapping for most of the case.

However, it is interesting that you can even preview it without assigning any material, even in the default Multitexture shading mode (just like when you drag and drop an local image onto a object in the scene). And of course, it cannot be rendered, since no material assigned.

Wow!!! you have got my attention , it DOES work , but in the render image some of it turns out like this?? ( i added a new picture )

I really wonder your settings for materal and texture. Would you also paste the screenshot for that? or we can go to the chatroom now :) (I'm in the one called Renderfarm).

ill post a picture now :)

You don't need to toggle off the color influence, in this case. So, toggle both Color and Alpha, as shown in my picture.

Ok i have it working  now :) Thank you very much


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How to lock group
Is there any locking of group. When we make a group and after selecting one part of the group the entire group does not move until Press Shit+G -> Group then its move. Or i have to go in the outliner and then click the select the group. Is there any method or addon that can lock all the object which ever part is select the entire group should move without going the process. (Pressing Shift+G -> group). Any suggestion or help Thanks
If i have square triangle and circle. Im a graphic designer i use coreldraw when i press group the selected object get group and when i click on any one object if it is triangle or square or circle the entire group moves If i hold ctrl and press any one only that object is move and in the above mention method it does not.

You can instanciate the group, and move the instance as a whole. Shift + A in the 3D Viewport -> Group Instance -> Choose your group

@aliasguru I think you did not get me what i mean. I have edited my question. If i have square triangle and circle. Im a graphic designer i use coreldraw when i press group the selected object get group and when i click on any one object if it is triangle or square or circle the entire group moves and in the above mention method it does not.

He got what you mean alright, but you did not understand his answer, see https://blender.stackexchange.com/questions/47295/sketchup-like-components-case-study-is-it-in-or-even-feasible/47311#47311

@DuarteFarrajotaRamos have a look at leon cheung answer thats what i need and he understood what i needed

You can set a custom keymap item for faster operation like that:

Go to File > User Preferences, switch to Input tab, expand 3D View > Object Mode:

Scroll down to the bottom of that category, find Add New button and click:

Define a new map item by setting parameters as shown below:

Here I define it with RMB double click, but you can always set another map as you want, as long as no conflicts with any other existing shortcuts. Don't forget clicking Save User Settings button when it's done.
I hope it can finally be faster and efficient enough:

Never even knew I could do this. Setting up right now!! thx

Have you tried creating a "null object / empty"  and parenting your meshes to the null/empty?
You can then move the null object (empty) around and the group would move.
Note: This concept is something I have used in various other software too, especially while controlling camera rigs. It might not be the best method, but it works.

You aren't adding empty to the group, you parented mesh objects to the empty.

@MrZak - Thank you for pointing it out. I realized I was using the "grouping" word a bit loosely while it has a completely different meaning in Blender probably. I have edited my answer to better reflect what I am doing. Hope this is correct.

What it comes down to is this:
In CorelDRAW, when objects are grouped together, the group automatically becomes the parent of its objects.
Not so in Blender where groups are more of an organizational concept. To get behaviour similar to what CorelDRAW exhibits, you need the empty cited in the previous answer. It then can be made the parent and you'll get what you're looking for.
Another way to achieve this 'group' behaviour is to use Ctrl-J to join your objects into one object. Then you would use Edit Mode to move individual 'objects' (which are actually discrete vertex meshes rather than objects in this case).
Hint: While in Edit Mode, hover your mouse pointer over a discrete mesh and hit Ctrl-L to select.

But the problem comes when it have many modifier and material used to different objects and not to simple object


text:
What causes odd deformations when using Subsurf?
first time here.
Alrighty, I'm quite new to 3D model design in Blender, but I have a little problem with my book model. The mesh is fine (I think). But there are a good few points where the text mesh goes wrong for some weird reason. If you need to know which version of Blender I'm using, it's Blender 2.69.
When I apply the "subdivision surface" modifier and set the subdivision render to 2, the faces go in and deform in certain areas. As far I'm not sure what is wrong at this point. I've taken two pictures just in case you need them.

Take note that I'm still unaware of some certain tools and common knowledge in Blender, go easy on the in depth reasons and fix details. Just simplify it please :)
Blend file :  http://www.pasteall.org/blend/30527

The one on the top looks like it's because of the four triangles. The one on the side might be because of an internal face, but it's hard to tell. Is it possible you could you upload your .blend?

I don't think so, I can email it to you though.

To upload .blend files you can use PasteAll.org.  It accepts images, .blend, and .py.  After it uploaded there, you copy the URL in the address bar and paste the address here.  Since you are new to this site, there may be a restriction on posting links.  I'm not sure about this last part.

You have some issues with the topology:

Extra edges on the large inner-top face, creating n-gons (also see this question):

To fix them, select them and press Delete > Edges.
Extra vertices on the edges, also creating n-gons:

To fix them, select them and press Delete > Dissolve vertices.
Internal edges on each corner:

To fix them, select them and press Delete > Edges.
Double vertices one of the corners:

To fix them, either merge them manually, or select everything (or just the area you want to check for doubles, but in this case it doesn't really matter) and press W > Remove Doubles.
No face on the top loop, creating non-manifold topology:
It's a bit hard to see, but if you select it with AltRMB and translate it, it's a bit more obvious:

You can select non-manifold geometry with CtrlAltShiftM.

Example .blend

Thank you very much, this answered my question without any problem encounters.


text:
Why do some bones in an animation lose their position when applying scale to their armature?
After starting with a stock armature with a run cycle I added a few of my own bones for various armor pieces on my model. As the stock model is too large for my game and the engine requires me to apply the correct scale before export I scaled the armature down (my mesh is a child of it). After applying the new scale and viewing my run cycle the bones from the stock armature I built on top of are fine, where my new bones explode out to new positions in all directions. It feels to me like the individual origins of my new bones are offset somehow, obviously I have missed a crucial step when adding them, what was this step, and how can this problem be fixed?
Before:

After applying scale:

Generally if an armature already has animation data, it's not safe to scale it and apply the transformation. It has something to do with changing the armature object's transformation matrix, because each keyframes in an action for a bone is recorded and evaluated against it.
To illustrate, here I have a keyframed armature, and I just add a free-floating bone parented to torso:

If I halve the armature's size in object mode, each bone's matrix stays the same:

But after I apply the scale transformation, it's a different matrix for each bones:

Whatever matrix operation is applied against the keyframe data, no longer turns out the correct transformation. In my experience, only free-floating bones are prone to this problem (the feet doesn't stray like this when animated in FK).

I invite correction, because my understanding of how transformation matrix works is still very limited.

Great answer, I was completely unaware of this. All the affected bones are parented but free floating, so I think you are on money with my issue. I'll try connecting them directly and report back.

@MarcusGorillius feel free to upvote the answer too if you found it useful.

@iKlsR Absolutely, as soon as I have 15 rep I will :)

@Adhi How did you add the matrix data to the view?

@stacker: I made a simple addon for learning about Blender's use of matrices.


text:
Strange uv problem
I am having a problem trying to texture my character his uv seems to be shaped strangely and I don't know how to make the texture work with it because of this

this is what it looks like

Try to triangulate the mesh with ctrl+t and then unwrap again.

Can you upload your .blend file to Blend Exchange?

Face on the background with diagonal line means some faces of the mesh weren't unwrapped (or their UV coordinates were reset). Several others pentagons are probably connected only with one vertex; you might want to reset UV map and unwrap again; or at least post some screenshots of the model.

I don't understand why triangulate mesh? It does not give me sense. He need mark seams (or mark it correctly) or use smart UV project. I my opinion triangulate mesh = more trouble than help in this case. :-)

Try using the Smart Uv Project option when you press U to unwrap.

Just leave the default settings and press "Ok"

That should help with the unwrapping, although it will probably not give you the exact results you need.  For that, there are plenty of great tutorials you could watch.  Here is one you could start with:  Character Unwrapping Tutorial


text:
How to animate fire without the fire freezing
I want to animate my fire effect and for some reason when i get it clipped into the scene it just freezes and does not flow like a fire should.

I apparently needed to adjust the start and end frame of the fire from thedomains smoke cache


text:
How do i copy and paste and objects location,rotation and scale at the same time
I have notice that when i do animations and make a mistake on where the camera should be its hard to fix it due to how long it takes to change its Locrotscale.
is there a faster way to copy it all and paste it to another frame.

While it is no one-click solution the Copy Attributes Menu Addon comes in handy for transferring locrotscale from one object to another. It comes with Blender but you have to activate it in User Preferences -> Add-ons (search for "attribute").
If activated you can select your target object, then Shift-Select your source object, hit Ctrl+C and select whatever option you want to copy first. Unfortunately there is no option to transfer all three options at once.

Is there a way to do this with a Pose IK, from one armature to another -- for example to have hands meet at a particular frame?

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


text:
Blender scene suddenly gets brighter and I can't undo it
I was trying to render my scene when I found that after a few rendering sessions the scene suddenly got brighter.
I can't undo it by lowering the emission of the object (if the objects have the emission nodes or any other bright nodes in the first place)
most of the objects use a toon shader but seems like even objects that are just colored and transparent are effected

And this is what it looked like after most of the scene suddenly got brighter
[

Under Render Properties go to Color Management (last row) then check View Transform make sure it's Filmic instead of Standard.

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


text:
How to make the mirror and actual mesh switch places
I am working on a model from a video from Daniel Kreuter and I made a mistake and but the head outline and eye outline on the opposite side.
i want to know how i can make the mesh and the mirror side switch places

Apply the mirror modifier. Delete the [vertices] you don't want. Add a mirror modifier. – cegaton 2 hours ago

0_0 omg i am ashamed that i was dumb enough not to think of that


text:
List of objects in appear in camera view (with script)
I would like to list the objects in front of the camera (What will be rendered). I'm thinking about the ray trace detection but maybe there are a better way.
There is exactly one element listed int the attached image because camera clipping and FOV. So the list will be depend from the camera settings.
I think this is extracted from Blender DATA but I don't know how.

Close to this: https://blender.stackexchange.com/questions/77607/how-to-get-the-3d-coordinates-of-the-visible-vertices-in-a-rendered-image-in-ble/77747#77747

Very similar to: https://blender.stackexchange.com/questions/45146/how-to-find-all-objects-in-the-cameras-view-with-python


text:
The soft bodies are attracted to each other. Why?
I created a scene with a rope (SoftBody) and two box with Collision only. The rope attracted to the boxes but I don't know why.
I created two videos: https://youtu.be/CWTQKD52Csg and https://youtu.be/BQJUS1dK6Vg
The Blender file: https://drive.google.com/file/d/1-33uqCH0g1cX0kcNvaC0VoW6tJxqkfVA/view?usp=sharing
Thanks.

Apply scale on all objects participating in the simulation, then make sure that they have appropriate normals in edit mode, then make sure that you delete any bakes and physics cache.  The negative scale on the collision bodies is turning their normals inside out, which means the only non-colliding position is inside the two cubes-- an impossible position.

I checked your file and first, I fixed the normals of the wire cube.  (flip normals)
I also applied the scale to the wire cube >  (ctlr+a) apply the scale.
But what really fixed it was altering the soft body and cloth physic :
Keep thickness outer the same but set inner to 0.001
That was a kinda weird problem to solve, I've never seen anything like it before.
In fact, I think this might be useful as well, lightning strike effects or so..

Thanks, And yes, This is a useful thing but in another role.


text:
Unable to find the input tab to provide the path for luxrender in blender 2.74
I'm pretty much new to LuxRender engine. I was trying to install LuxRender version 1.4 into Blender 2.74. But many tutorials out there seems to suggest that you need to provide the path to LuxRender after installing the same as addon. They also showed a screenshot where you need to enter the path in Blender 2.5x but I couldn't find anything like that in Blender 2.74 . ..  Kindly help me out.
I have attached screen shot in Blender 2.5x below. . .

I have also attached the screenshot in Blender 2.74 below. . . .

You can find it in the "Blender User Preferences" in the Addons tab, under the plugin Render:LuxRender.


text:
Mini bot animation using armatures and constraints
I am attempting an animation, a small bot like motion.

This is only one half of the animation and a bit more of the other half cycle.
The current animation is done using only one armature and couple of constraints. I was able to animate the first half by just rotating the  armature. The rest is manually keyed for reference.
The current setup is depicted below:

As an end goal, I would like to create an endless loop over curve paths.
Unfortunately, I am unable to arrive at a symmetric arrangement of armatures and constraints as they end up locking each other. In an ideal setup, I would assume that just rotating the armatures would suffice.
Kindly help me out with a setup that could work.


text:
Why is the result of this GLSL shader asymetric when rendering with stereo "Side-By-Side"?
I am trying to achieve an inverse lens ditortion for the Oculus Rift during Side-By-Side stereo in the game engine. I am using a custom Filter2D with this GLSL shader.
The distortion can be achieved as described here. Another fragment shader for that cause can be found in the OpenHMD examples.
The distortion looks good without stereo, but is asymmetric when I render it with Side-By-Side. For other stereo options, the output is not correct, but symmetric. Where is the problem here?
uniform sampler2D bgl_RenderedTexture;

const vec4 kappa = vec4(1.0,1.7,0.7,15.0);

uniform float screen_width;
uniform float screen_height;

const float scaleFactor = 0.9;

const vec2 leftCenter = vec2(0.25, 0.5);
const vec2 rightCenter = vec2(0.75, 0.5);

// Scales input texture coordinates for distortion.
vec2 hmdWarp(vec2 LensCenter, vec2 texCoord, vec2 Scale, vec2 ScaleIn) {
    vec2 theta = (texCoord - LensCenter) * ScaleIn;
    float rSq = theta.x * theta.x + theta.y * theta.y;
    vec2 rvector = theta * (kappa.x + kappa.y * rSq + kappa.z * rSq * rSq + kappa.w * rSq * rSq * rSq);
    vec2 tc = LensCenter + Scale * rvector;
    return tc;
}

bool validate(vec2 tc, int left_eye) {
    //keep within bounds of texture
    if ((left_eye == 1 && (tc.x < 0.0 || tc.x > 0.5)) ||
        (left_eye == 0 && (tc.x < 0.5 || tc.x > 1.0)) ||
        tc.y < 0.0 || tc.y > 1.0) {
        return false;
    }
    return true;
}

void main() {
    vec2 screen = vec2(screen_width, screen_height);

    float as = float(screen.x / 2.0) / float(screen.y);
    vec2 Scale = vec2(0.5, as);
    vec2 ScaleIn = vec2(2.0 * scaleFactor, 1.0 / as * scaleFactor);

    vec2 texCoord = gl_TexCoord[0].st;

    vec2 tc = vec2(0);
    vec4 color = vec4(0);

    if (texCoord.x < 0.5) {
        tc = hmdWarp(leftCenter, texCoord, Scale, ScaleIn );
        color = texture2D(bgl_RenderedTexture, tc);
        if (!validate(tc, 1))
            color = vec4(0);
    } else {
        tc = hmdWarp(rightCenter, texCoord, Scale, ScaleIn);
        color = texture2D(bgl_RenderedTexture, tc);
        if (!validate(tc, 0))
            color = vec4(0);
    }
    gl_FragColor = color;
}

These are my render results.
First Image: Rendered with Above-Below, the result is at least symmetric.
Second Image: Rendered with no stereo, looking good, but unusable for the glasses.
Third Image: Asymmetric Side-By-Side rendering cropped.
Fourth Image: Aysmmetric Side-By-Side rendering without crop (validate function commented out)
The relevant stereo code is in RAS_OpenGLRasterizer.cpp, but I couldn't find the cause of the asymmetry.
Edit: A blend file with this issue can be downloaded here

Can you provide a .blend file? I'm not sure how to hook up a GLSL post-processing filter to the game engine's final output. Without looking at it, it's hard to say if your input coordinates are off, or what.

Moguri answered my question on the forums by posting this patch that fixes the Filter 2D issue in Blender.
The patch:
diff --git blender/source/gameengine/Rasterizer/RAS_2DFilterManager.cpp blender/source/gameengine/Rasterizer/RAS_2DFilterManager.cpp index 79ce853..1781852 100644
--- blender/source/gameengine/Rasterizer/RAS_2DFilterManager.cpp
+++ blender/source/gameengine/Rasterizer/RAS_2DFilterManager.cpp @@ -429,6 +429,9 @@ void RAS_2DFilterManager::RenderFilters(RAS_ICanvas* canvas)
        glActiveTextureARB(GL_TEXTURE0);
        canvas->SetViewPort(0, 0, rect_width-1, rect_height-1);
+       RAS_Rect scissor_rect = canvas->GetDisplayArea();
+       glScissor(scissor_rect.GetLeft()+viewport[0], scissor_rect.GetBottom()+viewport[1], scissor_rect.GetWidth()+1, scissor_rect.GetHeight()+1);
+
        glDisable(GL_DEPTH_TEST);
        // in case the previous material was wire
        glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);

Note: This patch is already included in the trunk, verified at 08/25/2013

Please consider putting the solution here since link-only questions are not considered good.

@lubosz Thanks for your wrapper for the oculus rift. How should the wrapper installed in blender without distutils?


text:
Tips for proper topology
I'm confused on how topology works and the videos don't really help me much.
i am trying to make an anime characters face with a video from daniel and i am having trouble keeping a good topology.

Focus your question on specific details in which you are having difficulties, see this for additional help http://topology-guides.tumblr.com/

This a fairly large topic. But i try to give a rough overview that may serve as a general guideline for further investigation.
Main goals of good topology:

Animation friendly mesh
Being as low poly as possible

Why animation friendly:
In real world skin behaves like a tight layer that gets stretched by the muscles and bones right beneath it. Logically real skin does not have any polygons, meaning it bends right where the muscle is.
But in 3D we have polygons and this is a problem. Mesh deforms along the edge loops. If the edge loops and the desired wrinkles are not exactly at the same position, the mesh will deform not correctly, exposing the faces and creating artifacts.
Firt pragmatical fix, most of the people come up with "just increase the polycount until i see no more artifacts. But this is NOT how you do it. You want to keep your polycount as low as possible!
Why low poly:
Many inexperienced people think, their mesh only gets professional if it has a high polycount. But the opposite is the case! You need to keep your polycount low at all costs. Otherwise editing your mesh gets needlessly tedious. Also skinning (=weight painting the mesh to bones) your mesh gets more tricky. Not to mention it simply costs more compute power.
How to achieve animation friendly topology:
In general your mesh must follow roughly the form of the muscles and wrinkles of your model.
This means you have to look, where the muscles are and where they push the skin and where the skin forms wrinkles. Then try to build edge loops along those positions.
The face is especially tricky because there are lots of muscles at the same spot. Logically you can't rebuild all of them, because of "being low poly". So you have to find a good balance between those two rules. Mainly it depends on what amount of realism you are going for. If it is anime or toon style, you can ignore most of the muscles and just priorize the wrinkles of the skin. But if you are going for non stylized, pure realism, you have to study the human body and try to recreate most of the muscles in your topology.
Most important wrinkles of the head:

Eyes
Mouth
Nose
Jaw

If those parts don't have an edge loop, your head will most likely don't deform well.
How to achieve low poly:
Only set an edge loop where it is necessary! If the edge loop does not add anything to the mesh's detail, delete it. Use support edges wisely and with caution.
Where is the line between high and low poly:
Generally everything you model by hand, is still considered low poly. Modeling the mere foundation of wrinkles/creases is the highest form of low poly. If you are defining a complete shaped and sharp crease you are most likely already over the top of low poly.
Such fine details aswell as pores or mini wrinkles (like finger wrinkles) are not part of low poly and will be added using a normal and/or displacement map!
I created a pinterest side for some examples of good topology: https://de.pinterest.com/demons_fate/mesh-toplogy/

authors: Зинаида Лешёнок


text:
How do i add a certain amount of objects without lowering the frame rate?
I am making a combat animation and it involves a character fighting a large number of people. however the only problem is if i add too many the framerate drops drastically how do i fix this

There are many factors that determine frame rate.
Computer...Particles...
The complexity of the scene is one such and probably the reason why you are losing frames.
You can check the simplify box, but I for one wouldn't rely on that, it may help but not by much.

You can view everything in wireframe.
Another method is to use proxy characters in place of the 'final' characters.
Another method, that I use is to not use the in-blender time to base your animation judgment, instead take a video of yourself doing said action and place it in the bg, you can use that as your basis of time, action and reaction if you so require.
A good addon to said methods would to be to render the animation at a low resolution opengl render (after you had done...) that way you can check that the animation is too your liking without waiting for the long render times.


text:
How do connect this without ruining the topology
I am almost finished making this character butt I can't seem to connect her head to the back of her head.
i have a picture right here

I'm not an expert, but the below answer points you to specify which good topology you wish to preserve... if you need to animate the neck, you need to get good topology there, eg. There could be more solutions, depending on what you expect.

I am not sure of how it will lead your loops, however to keep it all quads I can think of those connections:


text:
How to make wind effect
I want to make a visible wind Blowing wind effect but i don't exactly know how to i have been messing with the setting for a while and so far smoke is the only one that seems to work.

Can you give an example of something that looks like what you want to achieve?

yes https://www.youtube.com/watch?v=0v2z-GmU2zA 0:19


text:
Motion blur glitching out on random frames
I am making a scene with a character spinning something around at high speed but for some reason when I use the motion blur located in the render properties
This happens
But it is supposed to stay like

This seems to happen on a 1 frame interval randomly throughout the animation. is there anyway I could fix it?

I wonder if there are not some bugs with the Motion Blur, have you tried to tweak the Shutter value or some other values and see what it gives?

I did try this and it seemed like it was fixing it for one frame and messing up others instead however after finding this I tried using the same new shutter on the frames the issue and there were still more issues.
the picture I've got her only happened the second go around


text:
How do I make an Npr shader that responds to lighting
I am trying to make an anime shader kind of like the one in the video below
https://www.youtube.com/watch?v=m52k-WP5HHQ&t=128s
However I want it to react to external lighting unlike what is shown in the video
I want it to be able to show the shadows of whats over it like how shadows of the hair will appear on the face when the strands are hanging down in front of the face.

This is the setup I have tried but when I use it I only get this

How do I make the shading to the spotlight I have on the left here?

Hello :). The get shading, you need to run the color output through a Shader.

Didn't work
Or I can't understand what you are saying
Changed the mix color node to a mix shader node and there was no difference

In your tree, the 'True Normal', (which is the unsmoothed, geometric normal in World space), is being used as the color of a Diffuse BSDF, before the light-response of the BSDF is extracted as a color, put through a B/W ramp, and used as a mask.
The True Normal is the direction of the geometric normal at the shading-point, encoded as a color in this case, and will not change with the light. It's in World space, so it will change when you rotate a non-spherical object shaded with it.
The BSDF will respond to the light, but by that time it's been colored, and the response will be affected by the color (which will be black, over a lot of the surface).
For NPR shading, you often do want to manipulate the the normals of a surface, but you would typically use the 'Normal' (which is smoothed) rather than the 'True Normal', and manipulate it on the way into the Normal, not the Color, input of the BSDF.
If you plug a color straight into a Material Output, it will be treated as if it went through an Emission shader, strength 1.
TL;DR
Unplug the Geometry node, color the BSDF white, and then you will find the light response of the surface acts as a mask between your two textures. The contrast of the mask will be controlled by the color-ramp. The textures will use the active UV map of the shaded object, unless you specify another.
I'd recommend installing the shipped add-on Node Wrangler, so you can ctrl-shift-click nodes on the way down the tree, and see what they're doing.

Simply unpluging the geometry node doesn't seem to work as it still only shows one color if I mess with the color ramp

@Aguest  Debug. Work your way back. What happens if you temporarily unplug the textures, too, and test the mask between two colors instead? What happens if you plug the BSDF straight into the output? Is the sphere shaded at all? Is the light strong enough/too strong? etc, etc. It's a process of elimination. Node Wrangler speeds that up a lot.

Unpluging the texture is color 2 does nothing,Unpluging the texture in color 1 makes it take on whatever color that color one has without a texture which I left alone so its white.
Pluging in the diffuse for the sphere though I found that the diffuse actually wasn't working either.
After checking things out from there I found that the average lighting from a spotlight wasn't enough for the color ramp to work.
Happy to know this but is there a way to lower the required level of strength for the lighting so that it still works with the usual amount it has?
can't fix with coloramp

Hi @Aguest, there are many variables, here. If you share your file on https://blend-exchange.giantcowfilms.com/, packing any (reasonably-sized) textures needed, and give an explanation of what you'd like to happen, I'd be happy to help put something together.

I am going to give you some links that have some amazingly advanced NPR shaders

(From Lightning boy studio ) https://m.youtube.com/watch?v=TpWI2rU8iF0
(From Creative blends) https://m.youtube.com/watch?v=o6CUFjOzrT0


text:
How do I avoid gaps to a mirror modifier when I am scaling a model vertices?
I was modelling the torso of a female body using the box model technique. Applied a mirror modifier and started to scale the mid section of it when a gap appeared. How do I fix or avoid this? Mirror Modifier Settings are as follows::
Axis: X - selected; Options: Merge, Clipping, Vertex G - all selected; Textures: nothing selected.

Check "Clipping" within the Mirror Modifier

they were not merged at the first place , to make sure they are merged select the middle verts and click S-X-0 ( resize to zero on X ), after they are merged they wont split again

Select all the vertices (Alt+RMB) that should be at the mid point, then press scale along the x axis(whichever is the horizontal one) and press zero (SX0) this will align them all in a straight line.

You can avoid it by turning on Clipping in Mirror Modifier.

Add more details, screenshot perhaps.


text:
Problems when rigging; only some of the object moves with rig even when automatically weighted?
I have this character I am trying to rig. I created the rig, and did not apply automatic weight yet. I have his hair in a separate object, so I joined the character and his hair with Ctrl+J. I then added automatic weight to the armature, but some of his hair does not move with him.
How can I fix this? Ctrl+P Keep Offset gives a similar issue.
Here is the blender file:
(The normal blender upload site doesnt seem to be working... heres a Mediafire)
https://www.mediafire.com/?kab867zkkh6snb4

After joining the hair with a body (Ctrl+J) assign the hair vertex group to the head bone with the weight value of 1.000. Please see these related answers: http://blender.stackexchange.com/questions/49388/how-to-get-disconnected-teeth-and-beard-to-move-with-rigged-face and http://blender.stackexchange.com/questions/8227/some-vertices-dont-move-along-with-the-rig

You may also use a simplier method. See my answer below.

Select the hair, then a head bone and press Ctrl+P-->Set Parent to-->Bone.

Thanks! Quick question, is there a way to parent it to multiple objects? Like if he had a shirt, how do I make the shirt wrap around his arms and body without poking through a ton? :o

I guess parenting the cloth to the bone won't work. You'll have to copy to weights of the body to the shirt to follow the bone properly. If you'll have problems with it ask a separate question and I'll try to help :).


text:
Extruding inwards along edges?
I have this shape that I want to extrude into. Here's a picture of the situation:

I want to extrude so that it fills in evenly so I can pull it out, add a mirror mod and have the blade looking all nice, however i cant seem to figure out how to extrude along edge normals. How can I do this?

You are looking for the inset tool. create a face from your edge boundary by selecting all vertices (like in your screenshot) and hit  f. Then hit i and drag with the mouse to create the faces.

Or, if you want to extrude to the normal of the face, use  f, then  e instead.

This worked! Required some cleanup, but was what I needed :)

After you E then middle mouse button and drag your mouse in the direction of the axis.
this will snap your extrusion to one of the three axis x/y/z


text:
How can I delete the bevel object once a curve is created?
I really like the curve feature. I think it has a lot of potential for creating curved objects for someone like myself who has a lot of difficulty creating a curve out of other meshes.
However, I really hate how curves pretty much need a bevel object, and that this bevel object CANNOT (to my knowledge) be deleted after the curved mesh is created.
Is there any way to create a curve, make a bend, have it be beveled, and not need a bevel object/be able to delete the bevel object afterwards?

Do you mean bevel?  Common practice is usually to put that sort of object on another layer which is not rendered.

No, the bevel objects needs to be kept around as long as you want the curve to be beveled. And it should be so as you can go back an change the bevel object curve as desired and it will update the bevel shape in your curve automatically.
If it gets in your way, you don't want it around, or you just feel its polluting your scene you can always hide it, move it to another layer or even place it it in a different scene in your blend file.
Alternatively if you are done modifying your curve and are absolutely sure you won't need to adjust it any further you can convert it to mesh with Alt + C > Mesh from curve as a final step.
You'll no longer need the bevel object but, this is discouraged and should only be used as a last resort, or if further modelling as mesh is needed, since it is a destructive procedure and you can't easily go back to non destructively editing both. Ideally do it to a duplicate of the object and keep a copy the original hidden.

How do I convert the curve to a mesh? That sounds like what I want to do.

The keyboard shortcut is Alt+C > Mesh from curve option

That will depend on the shape you want the bevel to be and whether you want to keep editing the curve. For odd shapes you will need to keep the bevel object as it defines the shape. You can hide the bevel object or move it to another layer to keep it out of the way. If you don't need to edit the tubing then you can setup your bevel and then convert it to a mesh with ⎇ AltC and delete the curve objects.
For simple bevel shapes you don't need to use a bevel object. A square tube can be created by adding a bevel depth and leaving the resolution at 0.

By increasing the resolution to 1 or 2 you get a hexagonal or octagonal shaped tubing, higher values give a rounded cylindrical tube.

If you want sharper edges you can add an edge split modifier.


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How to add some vertices from another object to the vertex object of one object?
I have a sailboat. I made a vertex group on the sail to keep it pinned to the mast, but the mast is a different object. How can I add the vertices on the mast to the vertex group to pin them together?

https://i.gyazo.com/db001a70c7d52ce8288159a9dd0efb08.png


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Rigging character; Keep Offset not working?
I am trying to follow this tutorial:
https://www.youtube.com/watch?v=cGvalWG8HBU
At 7:09 he makes the Leg IK bone keep it's offset against the Foot Bone. I am trying to do this, and I follow his steps but I do not get his result. Instead, I get this.

Additionally, the foot bone also clears it's parent and becomes separated. What am I doing wrong?

You have to jump into 'Pose Mode' right after parenting.  Then try rotating the bone.  From the looks of it, you have everything else right.

Is the foot bone supposed to be disconnected from the leg bone? :s

If the video is teaching the usual style of reverse-ik foot setup, then yes.  Is your rig behaving the way the video's is, if you go into pose mode right after parenting with offset?

Yeah, kept going and it works. One quick question lastly then Ill check this off. Im not sure if it was me doing this, but the origin (of anything in any mod) is following my 3D cursor. Is there any way to disable this?

Thanks!  You can change where/what the selected object (in any mode) rotates by selecting the Pivot submenu in the header of the 3d Viewport.  This is the button just right of the shading options (ie do you want wireframe vs. opengl vs. material)

Thank you so much that was irritating me to no end! Off to animating!


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How to cut line in a face without Knife?
I have this square and I want to make cut along the green lines.

The problem is, I try to use the knife tool (K+C) and the proper camera angling to connect the vertices and the edge, but the knife wont cut.
I want to be able to "loop divide" (line?) the face and drag a line so I can line the needed line to it's location. Or, atleast get the knife tool working properly.
How can I do this?

This looks like a case that knife tool should support - could you provide a Blend file?

To clarify, are you trying to cut four squares at the corners of the front face or cut the side faces from the back corner to the front edge?

Knife should work for this:

I suspect the darker face on the right is the result of a second, super-imposed face which is preventing the knife tool from working. To fix it, delete the face or use W> Remove Doubles:

That said, there might be a faster way to get the desired result, for example Subdivide and Bevel:

I also used triangulate (⎈ CtrlT) at the end; not sure if those diagonal edges were desired or not.


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How to edit Freestyle SVG exporter
I want to export a 2D DXF file including hidden lines.
I can set up 2 linetypes, "visible" and "hidden" and run the render.
I then open the svg file using Inkscape and saveas a DXF file.
However, both linetypes are allocated the same layer: "strokes".
I want the "hidden" linetype to be on a different layer. Is this possible?
Also, I would like to look at exporting the paths directly to DXF. Which Python scripts would I need to edit to do this? I'm not even sure it's within my capabilities, but would like to look at the code.

Even though the question is quite interesting, the way it's currenty written makes it a litte bit out of topic. The SVG produced by the Blender SVG exporter preserves the layers, they get lost in the DXF conversion. I would suggest to edit the question focusing on the last part. BTW, converting the SVG exporter to a DXF exporter sounds not an easy task!

why not ask the dev (Folkert de Vries) directly if he can add a mode to put certain lines types on different layers / group-elements. Or express interest in that being a feature.

Thank you both. So it's not a blender problem, it's the way Inkscape does the conversion? Makes sense I suppose. @Zeffi, I have taken your advice and posted a request on the project Github issues board. Thanks again, Dave

if you are really stuck perhaps you can save out two svgs, and convert them to two separate dxf and merge them in something like AutoCAD or DraftSight

Yes, that's how I was doing it before. I think my best solution is to write something quick and dirty in C or perhaps in Perl to take the SVG file and convert it directly to DXF. As Carlo suggests, the information is present in the SVG XML file, it should be easy enough to generate a DXF file from it.


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Attaching a flame system to an object
I have downloaded a BGE fire emitter file online. Now I would like to know if I could use this emitter to attach it to a vehicle and trigger the animation when the vehicle is collided. Is it possible?

You should post a snippet of your code here , so that others could review what have you been trying up to this point, most people are reluctant to help when it sounds like "Help me with my homework"

When your (not specified yet) emitter consists of an object that adds other objects from it's own position, you can parent it to another object. This way the newly added objects will be added at the current position of the emitter.
This is useful on engine trails, smoke, fire.


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Mesh Deform a complex grid with shape key, many problems
I’ve been trying to model a portable cd/radio device similar to the attached photo, with great success up to the point of the speakers. In most devices the speaker is covered with a metallic honeycomb grid. So, I decided not to use clip map and see the result in rendering but use actual geometry.
I’ve modeled a low poly surface (name Grid_orderR, 4k vertices) with shape key to deform the honeycomb grid (name honeycomb, 132k vertices). Object Grid_orderR has a Solidify modifier and object honeycomb has a mesh deform modifier. The problem is that nothing happens unless the thickness in solidify takes a high thickness value 0.3 in blender units. And then the deform has unexpected results because Solidify has overlapping areas due to the high thickness value.
Uploaded file includes the two objects without the deformers.
Any ideas?

[enter link description here][2]
Blend file for tests [2]: http://www.pasteall.org/blend/40068


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Assigning Shaders Based off UV Map Colours
I am wondering if it is possible to assign different shader's based off the colours of a Texture Painted UV Map that is assigned to an object? I've seen a couple of tutorials that use the Separate RGB node to split the colours, and then assign the shaders based off the result, but i was unsure if there was a simpler setup that followed a rule of 'if UV mapped texture = certain colour, assign this shader', possibly involving a ColorRamp node, for example?
Here is my progress so far:

Essentially each colour on the sphere would have a different shader assigned to it.
Thanks!

I'd say this is more work for Vertex colors and Vertex Paint. You paint there something on the mesh which will be a mask for shaders you'll add after that. In the material you add those vertex colors as a mask to the Factor input. It may be needed to add as many masks as there are shaders though but you really would specify " if certain colour, assign this shader ".

Sure, i did wonder whether vertex paint would be suitable for this, and it probably would be in this instance. As far as i knew though, for vertex painting to work well you have to follow the direction of placed vertices and edges of the mesh, whereas with texture painting colours can be painted smoothly across the surface of the mesh, without necessarily following topology?

Nope, there isn't an easier way.  Just use a Separate RGB node and plug the individual color channels into mix shaders.

Yes, that's really the downside of that method. You still can use almost this approach but painting a texture instead, so using Separate RGB node, as PGmath already mentioned and plug its data as a mask. Having texture like this you'll get something like this (the setup is quite messy, hope you get the idea).

@MrZak , thank you for the screenshots, what is the exact purpose of the ColorRamp Nodes in that instance? :) Carlo, That looks like it might be useful actually, i'll give it a look!

Solved it, using the Colour ID Mask Node Group in the other answer I was able to add it to several mix Shaders to separate the object's material based on it's UV Map. Tomorrow I'll write a more in depth solution below as i could cover it in a bit more than what is shown in the other answer, many thanks!


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Extremely Bizarre Mirror Result?
I'm trying to use the mirror mod to place hands on a character.
The origin is the direct centre of the scene and the mirror is placed on the Z axis, and yet I get this result:

The viewport is in direct front orthographic mode. Why is my mirror messed up?

It was the rotation and scale... I really must get in the habit of applying those more often...


text:
Making an elastic waistband on clothing?
I made these pants with this tutorial another user directed me: http://www.blendernation.com/2016/02/25/cloth-sewing-in-blender/
I followed the tutorial and got it to this:

I want to add an elastic waistband around the pant's waists and ankles so that the pants don't droop like that. How can I do this?

Try to use cloth pinning. See how it works here: https://www.youtube.com/watch?v=4cZAJ5aKwGo.

I dont want to pin the clothes though because I want it to travel with the character if he moves :/

Don't worry. Pinning obeys armature. Please see the example of my animation here: http://giphy.com/gifs/animation-3d-blender-xThuWdpRX2YsVDzfHy I've pinned the top of the cape, and as you can see all works fine. Just pin the vertices around the belt and ankles areas.

Im having difficulties hooking the vertex group of the top ring of the pants to the character. How do I pin these? :/ The tutorial doesnt go in detail to this.

Relatated previous post: http://blender.stackexchange.com/q/49180/2843

You may achieve the effect you want using a cloth pinning.

In Edit Mode select the vertices around the belt and ankles areas. Create a new vertex group and call it 'pin'. Assign vertices to that group.

In the Cloth settings check the Pinning checkbox and input the 'pin' group name below.

I can clearly see it work in your pictures, but for some reason my mind doesn't quite understand it; how does pinning the vertices of the pants objects keep the pant's pinned vertices group in relation to the (I think they're separate) objects of the microphone-shaped bone-looking objects? I just don't see where it's made distinct you want to pin to the leg/waist object, and not empty space >.<

See, when I do that, this is what happens:
https://i.gyazo.com/2d37473f934d48708537f348054a68ea.gif

Just parent the pants to the body (in Object Mode select the pants first, then select the body and press Ctrl+P-->Set Parent to-->Object) and it will follow it.

Aha! That... Woops. https://i.gyazo.com/3fae5dccd7a69a1083b32f62a635cff7.gif
It definitely is a step forward, but why are the pants slowly getting absorbed by his legs? : s The body does have collision on as well as the pants.

Would it help if I added my blend file? :s

The problem you've described is quite common. To avoid a cloth entering the mesh you have to play with its settings. Check out this answer:  http://blender.stackexchange.com/questions/43602/how-to-prevent-a-cloth-from-entering-another-mesh

Been playing with it, and its helping a little bit but not very much :/

Try to make the legs much thinner. As you can see in my .gif above it works quite fine then. Also I've noticed that the issue appears when you rapidly move the body. Try to move it slower. Sorry, but I have no other ideas how to help you right now :/. Though I'll try to update my answer, when I find a proper solution in future. Cheers :).

I suppose I could but I would prefer a solution that is more reliable :/ What do you normally do when you model pants on a character?

@elemein I just found out that you may increase the simulation steps to make it work well. Please check out this answer: https://blender.stackexchange.com/questions/30463/how-to-simulate-cloth-on-a-fast-moving-character


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Making pants hang off a body?
I've made pants, and I've made a body, and I lined the two up. What I want to do is the following:

Have the body not be affected by gravity, but still have collision against the pants.
Have the pants have "elastic waistbands" on the waist and ankles so that the pants stick to the body.
Have the pants have cloth physics with gravity, so that the body hangs to the body, but also hangs it's excess fabric, creating baggy pants.

How can I do this? :/

http://www.blendernation.com/2016/02/25/cloth-sewing-in-blender/

This tutorial is amazing! However I'm still having a small issue: Sometimes the cloth goes through the mesh of the body in some areas like the ankle. How can I fix this?


text:
Is it possible to group things as an object but keep materials?
I have this model:

Ideally, everything would be kept in one object, but I know if I Ctrl+J everything, it'll switch the materials to the dominant one. How can I fix this?

Ctrl+J should keep the same materials. If it doesn't then it's a bug and should be reported.

While joining shouldn't change the materials this question provides a couple of approaches to applying multiple materials.

@user3423509, it would be useful in trying to understand your issue if you would post a ~.blend file to a site like Blend-Exchange.


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Modeling from reference; how to not get messed up?
So I've started trying to model stuff from reference. I've gotten fairly OK results, but I keep running into some issues. The main one being, I could get the model perfectly lined up with one side of the reference photo, but then when I try lining it up in another reference photo, things don't go so well because there is a MESS of vertices everywhere! How can I stop from getting confused?
Example:

"Oh this is fairly clean, no issue."

"Geez Louise what is this mess!"

You can select only the geometry you want to edit and press ShiftH to Hide everything else but the selection.
From the Top View this looks unmanageable:

So we go to Side View, select only the vertices we need, and hide everything else. (ShiftH)

Of course the top view also shows just the vertices that we have left visible. Much easier to manage:

You can then reveal the hidden geometry again when you're done editing by pressing AltH
Extra tips
Although pressing ShiftH will hide everything but your selection, pressing just H will hide the selection and leave everything else as-is. Un-hiding is the same (AltH) no matter which Hide method you have used.
This also works in Object Mode. You can hide and reveal objects in the same way.

Try quad view
Model in solid view sometimes
Select vertices, use the hide vertices feature, to isolate a body part
Learn the numeric keypad keystrokes 1,3,5,7.
Rotate your view for fun via Mouse, Keypad Even numbers, Keyframed turntable
Of course you are using a Mirror Modifier for the symmetric being.
Render a low cost version every 15 minutes
Know how to move the reference photo.  Determine if the reference photo set is consistent and adjust if possible.  That means XYZ lines should line up across photos at key points such as head and feet.
With practice what seems like a giant headache today will be slightly smaller tomorrow
If you are sleeping regularly, not ingesting something bad, and not throwing up, the confusion is fine
Bigger Challenges await you

Nice tips man. You should write a coaching book ;).


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How to turn off partial wireframe?
I have this going on:

This "partial wireframe" thing is really annoying and I have no idea how I enabled it and I need to disable it.

Is this in Edit Mode or Object Mode? In case Edit Mode, are you using a Mirror Modifier?

Related - http://blender.stackexchange.com/questions/34245/edit-mode-transparent-objects and http://blender.stackexchange.com/questions/3328/selection-behavior-and-limit-selection-to-visible

Can you explain what you mean by partial? Is it bothering you that you see the mesh that is behind objects? Is it bothering you that you don't see the mirror of the mesh wireframe? Is there something else that you are concerned with?

I managed to fix it. It was caused by some button on the toolbar that had two boxes on it... Can't describe it much more :(


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Time remapping incompatible with particle info node?
I'm trying to make a spark material that fades to transparent as it reaches its lifetime limit. I've succeeded, but it absolutely does not work with time remapping for some reason. Here is my problem in video form:
http://sendvid.com/ajm6afu8
I multiply the lifetime by a factor of 12 in the node editor to keep it consistent with the time remapping (because the Particle Info node's lifetime output apparently doesn't scale with time remapping, but Age does), but the second the first particle hits its lifetime limit and disappears, every single particle fades at the same time. I don't know what to do and it's driving me crazy, because I need this to work for a more complex scene that I'm nearly done with. Does anyone know a way to fix this while still using time remapping?

Yeah, this is extremely unfortunate that the Particle Info node seems to not work with built-in time remapping. Not sure about the Time Remapping addon, but it unfortunately was not usable for rendering an animation with per-frame render time in excess of 1m 30s. Did you  ever find a solution to this?

This bug is known and unresolved https://developer.blender.org/T77307


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Cycles gives weird, blank output image while rendering
Render shader mode in the viewport is fine, but when rendering a final image, I get a strange black, blank image with a grainy, blurry light source as the only visible object. Anyone know what might be causing this? I made sure the correct camera was the active one. The strange thing is, the light source in the image doesn't correspond to the locations of my actual light source in the scene.  Here's the render output image:
And here's a screenshot of my viewport:

Do you have any renderlayers? Or perhaps other cameras? If not, is it possible you could upload your .blend?

Check your scene, layer and mask on Render layers settings. Maybe you made and object to act as a camera. Cycles render active?

@gandalf3 I have other scenes, and other cameras in those, but none are active, and I made sure the correct camera is active. Sometimes I will get nothing but a blurry light source, and sometimes I will get an image taken from the point of view of a camera that doesn't exist, WITH a blurry light source overlayed across the top. The results are wildly inconsistent sometimes, even when no settings have been changed, and the camera has just been moved. I think I may have set an object to be the camera, but I don't see how that's possible as I have an active camera. Will upload .blend.

@gandalf3 It would appear that I have solved the problem. The camera selected under "scene" settings was a different camera from the camera used in the scene I was working on. This led to the camera from Scene 17 (Camera.001 trying to render Scene 14, even though I had a camera from Scene 14 (Camera.003) set as the active camera. Under render layers, Scene 14 was set to render, even though a camera in Scene 17 was active, causing weird things to happen.

The problem is apparently that the camera that was selected under the "Scene" panel was different from the camera that was selected as active in the scene I was working on. The scene that was set to render under "Render Layers" was different from the scene that the "Scene" camera was in, and so this caused it to give a weird, black output. It's been solved. Cycles now gives a normal image output.

authors: Владислав Ткачев


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How do you make a cycles volume material fade to invisible at the edges?
I'm trying to model a spark using Andrew Price's tutorial (Blenderguru), but the sparks always look wrong. You can always see the outline of the ico sphere. I'm wondering if there's a way to soften the outside of the ico sphere (using volumetrics) to the point where it's invisible?
I know that one way to color depending on distance from the center of an object is to add a texture coordinate node, and then connect the object output to a spherical gradient texture node. This is what I have so far:

I know the solution is probably so simple but I've practically been pulling my hair out over this, and haven't been able to find anything about it online.

I've also wanted to do this for quite a while.

What if connecting BW ColorRamp to Fac socket of the Mix shader ? It seems to be created especially for that.

Apparently using a mapping node with a quadratic sphere texture gives the effect of faded edges... and it looks REALLY nice (especially with some tweaking). The node setup in the image I linked is what I used to get a sun-like fade-off effect at the edges.
If you copy the nodes on the underside of my node setup you should be fine, but one thing to keep in mind is that the quadratic sphere gradient is NOT automatically calculated from the center of the object. You'll have to manually adjust the X,Y,Z location on the mapping node to get the gradient's center to match the object's center. I had to eyeball it.
Also, changing the interpolation of the B/W color ramp in the image changes how quickly the color falls off, so it can blur the light at the edges even more. You can add extra control points to further control this.


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Combine Cycles passes in way compatible with photoshop
I'm trying to take my Cycles render passes into photoshop and combine them there. The purpose of this is to be able to manipulate the passes individually with various photoshop tools. However, photoshop does not support the way that Cycles passes are usually combined.
Normally, you have ((Diffuse Direct + Diffuse Indirect) * Diffuse Color) + ((Gloss Direct + Indirect) * Gloss Color). However, Photoshop does not have the Add blend mode.
So to do this, I need a different way to combine passes that does not rely on the Add blend mode. Is there another way that will be reasonably accurate?

Sure Photoshop has add mode, it's called Linear Dodge..

@Jerryno I've tried it. It is not the same as Add. It does other stuff as well and does not give the same results as Add in blender.

In Photoshop the add blending mode is named LinearDodge(Add). The reason why it might look to do incorrect results is due to the color space it operates in. To handle the data we need to work in linear space. If you want to do non-clamped, fully linear compositing, you need to use 32bit-mode, at all the times.
Export your layers as MultilayerEXR, import into Photoshop with EXR-IO addon. Photoshop will work in linear space when set to 32bit depth, which it is by default when opening EXR.
Set your layers to multiply and add like this:

You get the correct result. Next you want to convert this into Smart object, then convert to 8/16bits without merging layers and do whatever you want with it. Like this you can still work inside the Smart object in linear space.

You can also work in linear space when using 8/16bit depth, but you need to set it inside Edit > ColorSettings, because Photoshop does not default to it in 8/16bit depth. Use Custom profile with Gamma 1.0. Your monitor probably displays in sRGB, so you need to check View > Proof Colors, to see it converted into your monitors color space. Note that some color spaces do not offer the same gamut, so there will be losses when converting, which is un-avoidable. sRGB and linearRGB have the same color gamut, only the gamma curve is different, so the color space is no problem.
Photoshop is designed to handle whatever color space (CMYK, AdobeRGB, Linear, etc.) and does not only work in display-referred space.
But only in 32bit depth it is unclamped. Working in 8/16bit will result always in clamping and incorrect result because of this, not because of color space.

Explanation why this does not work in 8/16 bits:
When exporting the layers as png or tiff in 8 or 16bits, you loose accuracy there. You can export them as sRGB and composite in Photoshop in sRGB space with no problems. But color blending operations will result in clamping when not in 32bit, so another loss of accuracy.
You might loose some sharp highlights in 16bits and probably your image will look very different when using 8bits.

Thank you, that makes sense now. I don't suppose there's any way to do something similar in SAI paint? I wanted to do filters and PS and paint in SAI2. But looks like Sai is only 8 bit.

"Photoshop is designed to handle whatever color space (CMYK, AdobeRGB, Linear, etc.)" only one of those is a colour space. "and does not only work in display-referred space" Photoshop is display referred due to historical reasons, including the colour management system being largely display referred (ICC). These facets make Photoshop unsuitable for scene referred work. Everything from a majority of the PDF specification blend modes, to the ACE CMS (ICC), to lacklustre 32 bit mode, etc. essentially makes Photoshop useful for display referred work only.

@troy_s look up color spaces. You can definitely do scene referred editing in Photoshop through custom ICC profiles, but it's true that the 32-bit mode does not offer all the tools and so wouldn't be my weapon of choice also. I would do that in Krita. But this is about Photoshop. If you want all the tools Photoshop has, there is this workaround.

The V4 specification allows for parametric curves. You would need to find a single designed one to make a case however, as I have seen zero out in the wild. PS remains display referred. As for your comment about the term "colour space", I would recommend people look to the ISO 22028-1 Standard, which states very clearly that the term features three mandatory components: A) A white point, B) Transfer functions, C) Chromaticity of primaries. CMYK and Linear are a colour encoding model and a transfer characteristic respectively, not colour spaces. However, thanks for the tip.

According to this, Linear Dodge is the same as Add in Blender. However, if you are working with 8 or 16bit jpg/png/tga, Photoshop by default will works in display-referred space (i.e. everything is gamma corrected and non-linear), so the results of adding multiple render layers together in a non-linear space will be WRONG.
The only way to work in a linear space, which is absolutely critical, is to use 32bit EXR, that's the only way Photoshop will operate in linear space, and follow this workaround.
In short, don't use Photoshop. It's really not designed for linear values and will give you wrong results  unless you specifically configure it to work in linear space.

I'm working with 8 bit PNGs that I saved out of Blender. Is that why Linear Dodge 'add' isn't working then? Do I need to go through this as an EXR?

This answer is very misleading and except the "make sure you are in 32bit" and "dodge is same as add" wrong. See my answer for explanation.

Thanks Jerryno, i updated my answer to be a little less absolute.


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Show and Hide child objects along with Parent
I have several Parent objects that each have a lot of child objects. I need to key frame showing/hiding the various different stacks of objects at different points without it becoming too tedious. Ideally, i'd like it if I could set my child objects to share the show/hidden status of the parent object. Is this possible?
Alternatively, is there a way to keyframe the show/hide of a whole selection of objects at once?

I think, easiest way to do this - scale parent down to 0 in one frame.

As a comment, as I've no idea how it was done. I've seen something like that done through drivers. Alternatively, have one .blend for the object groups (each parent with its children as a group), and a second .blend for the animation, where you link to the groups in your first .blend (used as a library)?

This is a render time consideration, is that correct?

EDIT, much better way to do this using properties
https://blender.stackexchange.com/a/147144/15543
https://blender.stackexchange.com/a/197072/15543
Fudge the driver system 2.9x
I removed the previous answer re doing this in 2.8, don't really recommend this one..
Melodicpinpon asks

Would it work in 2.9 version? This question has been debated in many
places and this method could be the solution...

Using a method somewhat similar to @AtomicBezierSlinger can add a driver to every object in the scene that has a parent.
However the use of use self makes this driver readily copy pastable into other objects, without the need to check or set the parent object.
Here is a test script to add the driver to all objects with a parent.
import bpy

from bpy.app import driver_namespace as dns

def test(self, dg):
    vl = dg.view_layer
    return not self.parent.original.visible_get(view_layer=vl)

dns["test"] = test

context = bpy.context
scene = context.scene
#parented objects
parented = [o for o in scene.objects if o.parent]

for o in parented:
    #o.animation_data_clear() # testing
    #continue
    o.animation_data_create()
    fcurve = o.driver_add("hide_viewport")
    driver = fcurve.driver
    driver.expression = "test(self, depsgraph)"
    driver.use_self = True
    # dummy var to make driver update.
    var = driver.variables.new()
    var.name = "dummy" # frame
    var.targets[0].id_type = 'SCENE'
    var.targets[0].id = scene
    var.targets[0].data_path = "frame_current"

Making a test method and adding to the driver namespace is unnecessary as it can be directly crunched into expression field as
not self.parent.original.visible_get(view_layer=depsgraph.view_layer)

use self is not default and will need to be set.

answer below is for versions prior 2.8 with the use self option available.  Also not a recommended way to use driver system.

Fudge the driver system
Firstly we'll set up a custom driver that sets a property of all children recursively to the value of the parent.
import bpy

def traverse_tree(t):
    yield t
    for child in t.children:
        yield from traverse_tree(child)

def set_children(obj, prop):
    val = getattr(obj, prop, None)
    if val is not None:
        for c in traverse_tree(obj):
            setattr(c, prop, val)
    return val

bpy.app.driver_namespace["setchildprops"] = set_children

Now we can add a driver to a custom property on the same object as the property we wish to set on all children.
setchildprops(self, "hide")

making sure to check the non default "use_self" property of the driver.

Now if you keyframe the "hide" property of the same object it will hide / show children accordingly.  Note it will not update the UI automatically, until some property eg frame is updated.

Anyone tried this with 2.82 too?

Consider a driver which copies the Render Visibility value of the parent.  This will be successful.
The objects will still be available for [3D View Window] viewing.  Only you can determine if this arrangement  suits you.
You might even copy the [3D View Window] visibility based on the Render Visibility of the parent or any other object.
Please click on the image below to see a larger image.

The purple color on the visibility settings indicates a script.  The eye dropper was used for the target ... the parents render visibilty.  Arrow indicates the driver.
Consider the copy and paste of drivers from the context menu.
The contents of the driver are shown in the graph drivers pane.
You might even consider layer visibility to avoid clutter.
If you have a simple still shot ... you can move objects off the viewable area.  This idea is for simple circumstances only.


text:
Change field of a node in a group
I am trying to make a script that will change the value of a specific node within a specific node group. I have seen from this question how to target a node within a material, but I can't see how to change a node within a group.
The target node group exists within several materials, but the materials vary in different scenes, so I don't want to have the script change a specific material unless it has to be that way.
(Note: I know a more common way to solve this would be to use a Driver and Custom Property to change the value of the node, and then have the script change the property. However, I'm running into some issues getting my custom properties to update their drivers reliably, so I'm exploring other options too.)

Why you can't just use our nice script?

@brockmann I thought that was for replacing one node with another, not for changing the value of a node within a group? Will have to look again

It should also properly replace any group, otherwise let me know.

I don't want to replace the whole group, just change a value node within the group from 0 to 1.

I don't care. Just thought, duplicating the group, changing the value and replace all the nodes takes 5 seconds to do... @Drudge

That might work just as well actually.

You can directly access node group data from
node_group = bpy.data.node_groups['NodeGroup']

The node group name is the one chosen in the group node

Each node group then has it's own nodes -
node_group.nodes

You can find a node groups nodes from a material (don't confuse node name with node group name)
bpy.data.material['Material'].node_tree.nodes['Group'].node_tree.nodes

You can get the node group name from the materials group node in node_tree.name
for n in mat.node_tree.nodes:
    if n.type == 'GROUP':
        node_group_name = n.node_tree.name

See this answer for an example of creating a node group using python.
Once you have the group nodes you can access them the same as normal material nodes.
node_group.nodes['Diffuse BSDF'].inputs['Color'].default_value = (1.0,0.0,0.0,1.0)


text:
Roll view while looking through camera
I am painting grease pencil based on a fixed camera angle. The camera itself is locked and won't move. I am looking through it, but the camera is not locked to view, so I can still pan and zoom without moving the camera. It is projecting a background image that I am painting the grease pencil over. There are also 3D objects being painted over.
To make painting certain angles easier, i want to be able to rotate the canvas like you'd normally do in photoshop or SAI or Krita. But I can't find a way to do this while looking through a camera. In the Viewport camera, you can use shift+numpad 4 or 6 to roll it. This does not work when looking through a camera. If I unlock the camera and roll it, then my background image rotates with it, so that doesn't work.
I need some way to roll my view of the active camera without rotating the active camera itself. Is this possible?

As far as I know, if you rotate the camera, the background image will always rotate with it. However, similarly to this question, you can display the image inside of an empty instead of as a background image, and then you can roll your active camera, and the empty displaying the image won't move.

I realize that this isn't a perfect solution since using the empty isn't nearly as easy as just using the background image feature, but it's the best I can come up with.