text:
How to simulate molecular dynamics in Blender?
I need some effect like rustle or tremble or dynamics. I don't really know what's it in Blender, as I am a beginner. But I wish it could look like this.
If to describe it as a scenario + how and what:

Download a molecule from PDB.
Open file in PyMol & export the object as .obj file in this ball-and-stick form. Or in any other.
Now, till this point I knew what to do. How to make it all tremble like in dynamics? I think it may resemble a cut-wire with lightnings coming from it, you know all such curving.

I have been experimenting with this add on : http://www.blendernation.com/2016/04/28/jigglearmature-add-on/ .... If you can use an armature, it might get you to something like what you want...

What you show in that video seems to be some basic physics animation. Maybe look into this Molecular Addon https://www.youtube.com/watch?v=Rd4gsO2U6No download linki in the video description, and another video https://www.youtube.com/watch?v=_5QkPnPDcfc

@rcgauer the key word was really "jiggle", I've found several good videos on jiggling in blender. I will upload the answer soon, so everyone can see, though it's a bit messy, I need to prepare it first)) thx

Cool... I would be interested to see what you come up with. We work with natural systems and behaviors, and I look forward to seeing your approach.


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How to control particle's direction by animation node?
As title, i do not have any idea to control particle's direction by AN.

Use Force-field of type Curve Guide.

Are those particles from a particle system, or are they created in AN?

Made by particle system.

@EthanLiu Did you try Jaroslav's suggestion?

@OmarAhmad i know how to use curve guide force.
Just want to know is it possible to control particle by AN.

Oh, so you want to define the velocity/acceleration of the particles (Their direction and speed)? If so, unfortunately, there is no way to do that in AN. Blender doesn't allow it.

@OmarAhmad, thanks for your help.By the way, is it possible to control in the Everything Node in the future.

@EthanLiu Probably yes.

There is no way to alter the velocity or acceleration of particles of particle systems, the Blender python API doesn't allow it. However, if you want to control the general direction of particles, you can instance force fields and control their orientation and strength as suggested by  Jaroslav Jerryno. As an example, lets create a spiral spline in Animation Node and enable Curve Guide Force Field and Path Animation for it:

Or perhaps by animating a wind force field:

Wow, this is brilliant. This is really useful creating fizzy drinks with all those bubbles.

source: Stack Exchange

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

sort: votes


text:
How to make different objects follow and bend with different curves with AN?
how to make each lines to follow each curves as my pic shows?

Please search .. Curve Modifier ... here at BSE and other places. Look for tutorials on the website that ryhmes with noonoob.  In my opinion your question is unclear, and can be improved by you.  Yet I took a guess under the cirumstances.  I am not sure why you need AN for this.  Please show any AN you have in screen captures.

I have 200 different objects, and i need make then to follow 200 different curve as couple.So i need some way to a achieve it.

Please show your work for one.

I shall describe a method to deform an object along a spline. You can extend that to multiple splines/objects using a simple loop.
First, we choose one of the local axis of the target mesh to be the axis along the spline tangent, let that be x in this demonstration. We then get the vertices locations in the local space of the mesh, and normalize the chosen local axis such that it ranges between zero and one, this can be done by remapping it based on the local bounding box, however, for simplicity, we are going to use the value of the x dimensions.

Then, the normalized x locations are used as the parameters of the spline evaluation process, the tangent and normal are normalized and the cotangent is computed using the cross product. Then, a linear combination of the tangent, normal, and cotangent is computed using the x, y, and z locations of the vertices as the coefficients respectively. Then the evaluated locations are added.

Finally, a new mesh is constructed from those vertices and output.

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


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How do I stretch my object from one point to the other?

Just wondering how I could get my object (the truss) to stretch and become the same size and shape like the cube behind it.
Thanks.

scaling along one axis seems obvious, why it's not working?

Mostly because the truss itself is at an angle. (Like 5 degrees on the z-axis)

I think you can solve this with snapping and transforms with cursor as pivot. I tried to rebuild a situation similar to what I see in your picture, so that the truss is of different size and rotation than the other shape:

First of all, switch to top view, and activate vertex snapping like below:

Then, translate the truss towards the other shape, and snap a corner vertex as below:

Then, go into edit mode (of the truss) and select one corner vertex, then snap the 3D cursor to it.

Now you can activate cursor pivoting, and rotate the truss

...until its upper vertex snaps to the other shape, perfectly:

Now the different angle is gone, and you can switch to front view, to stretch (scaling) the truss until it matches (snapping) the other shape perfectly:

Does this solve your issue?

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


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character splits in half when moving leg
I'm new to Blender and playing around a little bit, trying to make a decent enough character that can walk and what not. My problem is, so far all of my rigs seem to split in half when I move the leg. The lower torso moves with the leg and the belly pretty much gets cut open up to the belly button.

When I modeled the character I applied a mirror modifier. Could that be the reason? If so, what did I do wrong?
Is there any way to fix this without having to start over?
Thanks!

To avoid this problem you should had the "clipping" option checked in the mirror modifier. Now simply go to rest pose (select all bones, then press Ctrl+G, Ctrl+R, Ctrl+S), then in edit mode select all and remove doubles, or manually join (Alt+M) the unconnected vertices, which probably are one on top of the other.

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


text:
Try use option Freestyle in script for Blender
I'm about to write a script that allows to make "true" the options (Freestyle in Blender):

Here is the python script I 'm writing to try to use options Script python
import bpy

sceneR = bpy.context.scene

freestyle = sceneR.render.layers.active.freestyle_settings
linestyle = bpy.types.FreestyleLineSet
sceneR.render.use_freestyle = True
sceneR.svg_export.use_svg_export = True
freestyle.use_smoothness = True
freestyle.use_culling = True
linestyle.select_by_visibility = True
linestyle.select_by_edge_types = True
linestyle.visiblity = 'RANGE'
linestyle.select_silhouette = True

I found it in the window "info" Blender indicating each action done in Blender
my problem is that when I run the script it that nothing happens , and options (circled in red on the first picture) are always off or False .
Do I put the wrong way , is there a different way to activate this option in a script?

You are close, the use of bpy.types.FreestyleLineSet is wrong as this refers to the class definitions used elsewhere. The correct way to add a new lineset is freestyle.linesets.new('mylineset'), you also have a typo in linestyle.visiblity = 'RANGE'
A working version of your example is
import bpy

sceneR = bpy.context.scene
freestyle = sceneR.render.layers.active.freestyle_settings

linestyle = freestyle.linesets.new('mylineset')
sceneR.render.use_freestyle = True
sceneR.svg_export.use_svg_export = True
freestyle.use_smoothness = True
freestyle.use_culling = True
linestyle.select_by_visibility = True
linestyle.select_by_edge_types = True
linestyle.visibility = 'RANGE'
linestyle.select_silhouette = True

In your code you have linestyle.visiblity = 'RANGE' - with a missing i in visibility the silhouette setting should be right.


text:
Bone heat weighting: failed to find solution for one or more bones (tried all "solutions")
So I've been trying to create this mesh for a while, and the rigging is the only problem I've had so far. I'm trying to rig just the head of a dragon, and I keep getting the same error message over and over when applying the automatic weights "Bone heat weighting: Failed to find a solution for one or more bones". I have tried all the fixes for this I've seen, such as decimating and subdividing the mesh, making sure the mesh is symmetrical across the x axis, making sure the origin for the bones and the mesh is at the center of the mesh geometry. Is there anything else here I should try? If you would like to try for yourself, I can email the file to you should you be interested. Any insights and help is greatly appreciated!

Could you please upload your .blend file to be able to help you?

You could try this

I know this is old, I'm just doing what I can to get all of these same questions linked back to a single, canonical version of the question.

The mesh should be manifold (no doubles, no internal geometry, no holes, no spare parts, no intersections between geometries) to be sure the automatic weighting goes OK.
You can break your model into different objects to understand where lies the problem.
Apply rotation and scale, and modifiers.
Sometimes temporarily adding a subsurf modifier to the mesh helps the algorithm.
If not, use manual weighting or upload the file for help.


text:
How to cut sphere with sphere? Topology problem
Basically it is a letter N. Tried many ways with no luck or lack...of knowledge.. :)  trying to make my own logo to 3d. Using boolean and rotating spheres, but topology is big problem.

Any suggestions?

Are you familiar with manual retopoligize?

Yes, but somehow, it never looks how it should be. Apparently I'm not too good at manual retopologizing...I was kinda hoping there is some automatic way

If nobody anwser this I'll try to make it tomorrow.

Thank you. I'm still trying...If somehow I manage to make it, I will post it here...

@RobertNol Try to rotate the sphere 45 degrees and then add boolean.

@RobertNol Bad news, I didn't found any auto method for this shape. I've tried quick retopo: http://imgur.com/a/s6d73. I'ts ugly with bad edge loop flow but it was just a test. You'll need to reptopologize only 1/4 of the mesh, then mirror it and then copy, rotate and manualy join.

@Denis I tried many rotations, tried even with ico sphere, and than with combination of ico and uv sphere...

@LukeD You are right, I will need to do it manualy. Thanks a lot  for tip 1/4, I'll give it a try.

Feel free to ask if you need some more tips. To retopo I'm using only F2 addon and standard extrude/fill techniques. With face snapping of course.

Do the edges need to be rounded or could they be sharp?

Sorry for late answer, I did it...manualy...It was hard, but I did it...Thanks

It's possible to avoid much work here with simple inset. It won't provide great topology straight away, it will add loopcut all over the corners where sharpening is needed in order to add Subsurf.

When you have a letter just after the Boolean chances are it looks something like tris, lack of continous loops etc. Select the part with indentations (the one you'd like to sharpen out):

Invert the selection (most likely face selection will be the most comfortable). It's also possible to use Outset option by pressing O while Inset is active; then insetting will happen outwards and this step should be skipped:

Then inset with I. There will be some areas where inset will create self-intersecting geometry, some cleaning work will be needed. However it might not be necessary to do it for all the letter (although it all depends on the final result as always):

I think your mesh is not fine enough to start with. Add a subdivision surface modifier and repeat the bool operation and you will get a smooth result.

Didn't work...Edges still not looking right. Looking better but not how it should be.

How many subdivision levels did you add? Try to add three or four levels to each of the bool objects, hit "apply" on the modifiers (not necessary, I think, but just to be on the safe side) and then do the bool operation. That should give you plenty of faces to get a smooth result. Subsurf info: https://www.blender.org/manual/modeling/modifiers/generate/subsurf.html


text:
How to render curves (or a faceless mesh)
I'm experimenting with geometry nodes in Blender 3.1 alpha, and used the following spaghetti of nodes to draw a trefoil:

The result is what I expect, shown in the viewport from the camera angle here:

Now I would like to render the result, either as a line as shown here, or as some thin tube with a usual material. A few things I've tried:

Setting Object Data Properties » Geometry » Bevel » Depth — this doesn't seem to work when I use a Geometry Nodes modifier (it works with simple bezier curves without a modifier).
Using the freestyle renderer — it won't render the edges, presumably because there are no faces attached.
Attaching a face and then using the freestyle renderer — I can add a face using the "Fill Curve" node, but then it flattens the whole curve in the Z axes.

What I'd like is some sort of wireframe rendering that works with objects that have geometry nodes attached and no faces (because no face could be added due to the topology of the curve).

Blender 3.0 isn't due for release until next month, let alone 3.1 so you're unlikely to get an answer here for any unsupported experimental version.

Well, it's destructive but you could apply the Geometry Nodes modifier?

If this is maintained in the latest version of Blender, I would report it as a bug. The geometry beveling should work.

I’m voting to close this question as off topic because it is about troubleshooting temporary issues with unfinished under development experimental versions of software, which are expected to be working properly upon stable release. This produces a question unlikely to be useful for future users, rendering its long term value low, making it unsuited for this site.

Thanks for the suggestion @DuarteFarrajotaRamos; I'll go ahead and report a bug.

Why not use a Curve to Mesh with a Curve Circle as Profile Curve?

Not sure of the result in your case, but you could perhaps add a Skin modifier after the GeoNodes. On my (much simpler) test it works well enough

The Skin modifier is only available for mesh objects, and I'm adding my geometry nodes to a curve object, so the Skin modifier is not available. That said, I tried using a mesh as the base object, then the skin modifier is available, but not applied, even after applying the geometry nodes (!), I think this could be a bug. The problem only appears though when I don't use the Group Input node, and instead generate my own input using one of the primitives (e.g. Mesh Line or Curve Line). After applying the geometry node, adding a new Skin modifier works.


text:
How does Blender decide random physics events?
I placed a cube over a plane and made both of them rigid bodies, and gave the cube a box shape under the rigid body options (the cube is active and the plane is passive). The bottom of the cube is parallel to the plane. However, when the cube falls, it doesn't bounce straight up, but in the way you would expect a die to bounce. It seems to me that Blender is adding some sort of random variable to the collision, but it falls exactly the same way every time. I'd like to make the cube fall in several different ways. Is the "random variable" for the collision seeded in some way, and can I change the seed?

Sims use random numbers, but they aren't really random, using the same seed will always give the same sequence of numbers. Most sims have a seed value but it looks like the seed used for rigid body is based on object data, you can move a vertex slightly and get a different sim.


text:
How can I turn off mirroring in sculpt mode?
So, I am extremely new to blender, I am going to say outright. I have tried to fix this, but i can't seem to find any option that would fix the problem. When I sculpt on an object, it directly mirrors it, even though i have not enabled the mirror function, let alone touch it. I have double checked to make sure mirror wasn't on and it wasn't. and so on and so forth. I pretty much haven't changed any options or anything. if you could help me figure this out, that would be nice.

If you want to disable/enable symmetry when sculpting, go to sculpt mode, then select/deselect the axes in the tool panel under the Symmetry/Lock section.

See Also :
How to disable Symmetrize in Sculpt Mode?


text:
Adding a pole target causes bones to ignore their IK constraints
I currently have a robotic arm rig with the shoulder only being able to rotate along 1 axis, and the bicep only being allowed to rotate along a different axis. I am controlling these bones with an IK controller, and It's working great, save for the fact that when I add a pole target to adjust the solution, all of my axis locks are ignored.
This issue has been driving me crazy, and I am wondering if there is a solution.
Here is the blend file : as you can see, the rig works exactly as intended, but when you set the pole target as the bone labeled "elbow" the axis locks are ignored.

As it turns out, this is impossible. The issue of ik constraints being ignored because of a pole target is a known problem. Hopefully support for this function will be added in the future. I might have to look into fixing it myself.

Change the axis limit of the bicep and shoulder like this.

Activate the axes display in the Armature panel.
You will see that the correct axis to unlock is the Z instead of the X.
You can also change the manipulator to normal or local, to see this more clearly.
When the unlimited axis is the X the IK constraint can't bend in the desired way.

This does not change the fact that adding a pole target for the IK chain invalidates the IK constraints.

You are right, I edited the post to clarify the steps to solve this.

You're correct, HOWEVER this does not apply if the ik chain has a pole target.

In this new image, you can see that the pole bone is set and working properly.

This does not solve the issue, because the shoulder bone is now rotating about 2 axes. The pole bone is overriding the rotation locks on the shoulder bone and the bicep bone.

Well, the pole won't override the locks, but it' will conflict with them. The locks prevent a bone to rotate in certain axis, thats it's purpose. The pole tells the IK chain to position it self towards it. Normally, one doesn't add the shoulder bone to the IK chain, just the bicep one. Maybe you would like a different setup? In any case, there's not a malfunction of the settings :)


text:
Is there anyway to change the rotation mode of multiple bones at once?
I am tired of manually switching from Quaternion rotation mode to XYZ euler mode for every bone. Is there anyway to accelerate this process? Any help would be appreciated!

Here is a script that will change all the pose bone rotation mode to the value set for to_mode in this case 'XYZ' for XYZ Euler Rotation on the active (context) object.
import bpy
from bpy import context

to_mode = 'XYZ'
arm = context.object

for pb in arm.pose.bones:
    pb.rotation_mode = to_mode

Possibly more useful to use context.selected_pose_bones which will set the mode only for those pose bones selected.
import bpy
from bpy import context

to_mode = 'XYZ'

for pb in context.selected_pose_bones:
    pb.rotation_mode = to_mode


text:
Where is Polysphere?
Where is the Polysphere object in Blender 2.76b? I have already installed Add Mesh: Extra Objects add-on and can see new objects in add menu, but Polysphere is not there. I also tried following it on the official page, but they say that the script is already part of Blender and is not needed to be installed from file. Clicking on the Current version download link opens a forum instead of the script.

Round Cube
I don't know if the codes comes from the "original" polysphere script, but with Extra Object add-on comes an operator called "Round Cube" which create a very similar geometry.

You'll just have to make sure to use the "Quadsphere" preset:

You can get the "original" polysphere script for pre-2.61 Blender version from the author website and then append the object in your scene (if you want to use a more recent version).
It seems to be slightly difference between the loopcuts position of the object created with the two methods.

Thank you. This almost is the answer. Is there any way to confirm that a "Round Cube" is geometrically the same as what they called a "Polysphere" and it is just the name that is different? Means if an online tutorial uses Polysphere, can I follow it with a Round Cube instead?

dotNeT, I did an online image search for "polysphere", and the images I saw, including the ones included on Blender 2.5x and 2.6x addons to add one to a Blender scene, all had very similar geometry to that pictured in Carlo's answer. For my purposes, anyway, they are "geometrically the same".

It really depends on the kind of tutorial you are following, but for the common usage (basemesh for sculpting), as @brasshat said, the shapes can be said having almost the same geometry.

I bet it's the tutorial about making a Basket ball "I guess by Blender Guru", I went through this, I had to figure out myself that Round Cube is Polysphere, with a new name.

Poly-sphere is something special.  The symmetry loops on the poly-sphere should form a perfect polygonal circle made of edges with equal length.
Rounded cube or any sub-divided cube with a spherify modifier or manipulated to be spherical only give you an incorrect version of the poly-sphere.
Example, create a cylinder with 16 edges.  Create a perfect poly-sphere with same diameter and segments on the perimeter.  Cut the poly-sphere in half and remove the caps on the cylinder.  Match the half sphere onto the cylinder's open cap, and try remove-double with threshold distance of 0 or barely 0.  If what you created is truly a poly-sphere, it should merge perfectly with the uncapped cylinder.
Blender by default does not give you the perfect and real poly-sphere.  It should be possible to create perfect poly-spheres by codes.


text:
Animation Nodes 2.1 strange bug
If I try to insert Mesh > Mesh from Object, I see the following error:

This is Blender 2.79b and Animation Nodes 2.1.2. Strange thing is that this thing was working fine a couple of days ago when I started learning about Animation Nodes.
Things I have tried:

Adding other nodes before adding Mesh from Object.
Removing Animation Nodes addon and reinstalling.
Removing the entire Animation Nodes folder from blender addons.
Uninstalling and reinstalling Blender.

Looking at the bug text, however it appears to be a problem within the code. Anyone knows how to fix it?

This node has been removed from Animation Nodes in newer version, and the developer forget to remove it from the menu hence the bug. You can get the same data from the Mesh Object Input node. If you get errors/bugs, report it to the developers directly. Like this.

I'm voting to close this question as off-topic because this question appears to be about an issue caused by a bug in Animation Nodes. Which was reported here.


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Displacement maps in Eevee
How do I apply Displacement map in Eevee? Unlike Cycles, the Output node in Eevee does not have any input for Displacement.

Use a displacement modifier instead, or use a bump map

@DuarteFarrajotaRamos: Thanks, but there is no input for bump map either.

You need to add a vector > bump map node to convert the texture into normal and feed it to the normal input of the eevee node.

@Cebbi you should probably post that as an answer below. Just elaborate a bit on how to do it and why, if relevant add some screenshots.


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Cycles is painfully slow even for the simplest of scenes
Google shows that Blender's slow rendering has been questioned numerous number of times before too, but in my case it has gone to a degree that rendering even the simplest things requires ages. I'm using latest 2.78a version on Windows 10.
I understand that my machine is a humble one by any stretch (i5 + 8GB + Samsung 850 Pro SSD), but my expectation was that simple scenes involving a few cubes, one light source, one camera and a handful of materials would render in about a couple of minutes or less. Instead it takes the likes of 15 to 20 minutes every time I press F12 (blender says the scene has 1 lamp, 5 objects, 63 faces and 72 vertices, which I believe is pretty simple).
I have tried the following already. Doesn't make a considerable difference in rendering time:

Changing from CPU to OpenCL: throws error when loading libraries.
Changing Sampling: From 128/32 to 12/6.
Changing Light Bounces: From 12 to 4.
Changing Tile Size: From 64 to 256.

My gut feeling is that this has something to do with Windows 10, but I don't have Windows 7 or XP right now to test if that is the case. Has anyone else experienced this? Any other solutions to make it faster?

What are your specs? Also, this may help

One solution is to boot a linux livecd to use blender. In my case cycles on linux renders just shy of 40% faster

lol you don't know what slow is until you try to cycle render on a laptop with a AMD Turion 2 m500 CPU. 40+ seconds to render in cycle. The more cores your CPU has, the better. I recommend a 8 core CPU.

Make sure you dont have "Square Samples" checked.

If you are using CPU don't make large tile sizes. Experiment a little for your device specifically, but unless you have a good GPU, large tile sizes will just make blender run slower.
It could just be that your computer is slow, but, I have an i5 and I can render things at decent speeds. (Maybe try rebooting and closing all other applications. You could have bloatware open or something)
The real thing that affects render time is how many samples you use. Changing that to be smaller will allow you to get faster lower quality renders.

One thing that really helps if you're doing very simple bakes (e.g. diffuse/color only) - such as you would do for combining or splitting diffuse maps, is to drop the render passes under Sampling to 1.
It's probably NOT a great idea if you're doing anything where the bake truly relies on engine rendering functionality (light map bakes, AO, transmission, subsurface, etc.), but for the simple types of bakes I often do when creating a new model or working on UV maps, setting the output size and tile size to the bake size and dropping rays to 1 seems to work great, and it drops the bake time down to seconds even for 8k maps.


text:
How to make a smooth oval window
Here is a simple model that I'm working on:

I want to make the selected ring of edges smooth, to get rid of the discrete angles and get an oval shape. Something like this:

I have tried applying subdiv modifier but that changes its shape to a multi-point star. Also it smooths outer edge of the cube too, which I do not want. I have also tried Ctrl + R, but that does work on the selected face, only on the outer faces. Lastly I have tried Alt + Shift + S, which only changes the size of this face but doesn't do the smoothing that I want.

can you upload an image of your multipoint star? can you elaborate why cegaton's workflow didn't suffice?

I didn't say cegaton's workflow didn't work. I just checked it and it works.

You can try "subdivide smooth" in edit mode

I would suggest entering edit mode, switching to edge selection (CTRL+TAB from the 3D View, or one of the boxes next to transform orientation), and selecting the outer edge of the circular window. From there, within the 3D viewport, hit CTRL+B for beveling.
You'll note that moving the mouse will scale a face where the edge used to be. By rolling the mouse wheel, you can change the number of edges within it. Scale it up to four or five, and you should have a satisfactory rounding of the edge.
(As a side note, the reason that CTRL+R doesn't work is that it only operates on quads; and your inner face is not four sided, it's twelve sided. So that won't help you here.)

Thanks. I tried this and it does actually create faces around the outer boundary, but those "edge loops" still have the same number of vertices as the original edge loop, so it is not getting any smoother or roundish. I tried creating more faces too (using scroll wheel), but that only creates more loops, with the same number of vertices and same angles between consecutive vertices.


text:
Color faces of a from_pydata mesh depending on face height
I have some scientific data that I am importing into blender for rendering. I'm trying to make a Surface plot plot with a color code.
Scavenging around I found a python script to produce the mesh. I just cannot figure out how to give every surface a different color depending on its height, or even a material.
Here is the code. Any help would be appreciated:
import bpy
import math
import numpy as np

x,y=np.meshgrid(np.arange(-100,100),np.arange(-100,100))
r=np.sqrt(x*x+y*y)
values=np.sin(r/10.)
# clear mesh and object
for item in bpy.context.scene.objects:
    if item.type == 'MESH':
        bpy.context.scene.objects.unlink(item)
for item in bpy.data.objects:
    if item.type == 'MESH':
        bpy.data.objects.remove(item)
for item in bpy.data.meshes:
    bpy.data.meshes.remove(item)
for item in bpy.data.materials:
    bpy.data.materials.remove(item)

# mesh arrays
verts = []
faces = []

# mesh variables
numX = np.shape(values)[0]
numY = np.shape(values)[1]
scale=2. #how large you want to make the field in x y
# fill verts array
for i in range (0, numX):
    for j in range(0,numY):
        # nomalize range
        x = 2*(i/numX-1/2)
        y = 2*(j/numY-1/2)

        z = values[i,j]

        vert = (x*scale,y*scale,z)
        verts.append(vert)

# fill faces array
count = 0
for i in range (0, numY *(numX-1)):
    if count < numY-1:
        A = i
        B = i+1
        C = (i+numY)+1
        D = (i+numY)
        face = (A,B,C,D)
        faces.append(face)
        count = count + 1
    else:
        count = 0

# create mesh and object
mesh = bpy.data.meshes.new("wave")
object = bpy.data.objects.new("wave",mesh)

# set mesh location
object.location = (0,0,0)
bpy.context.scene.objects.link(object)

# create mesh from python data
mesh.from_pydata(verts,[],faces)
mesh.update(calc_edges=True)

Thank you. What did you use to render ? In cycles I do not see any change for the colors

Use a material if you can. I read this too fast and thought you wanted to set a Vertex Color layer.

I usually do it with the following node setup:


text:
Correct use of Boolean modifier?
At its simplest, I have two objects. The first is a modified block. Then I add a cylinder, shaped like I want. This is to be joined to one end of the block.
If I move the cylinder into the position that I want, it seems I am getting an automatic union of the two objects. If I select the block to begin the Boolean union sequence, I find that both objects are selected. I cannot separate the two objects to try again.
I have to be doing something wrong, but I’m stuck. Any suggestions?
Oh yes, sorry. I’m using Blender 2.81a.
Regards.

Do you speak about Boolean modifier https://docs.blender.org/manual/en/latest/modeling/modifiers/generate/booleans.html , Intersect (boolean) operator, or BoolTool add-on https://docs.blender.org/manual/en/latest/addons/object/bool_tools.html?


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Something is wrong with io_export_md3.py
I try to export mesh to md3 format using script taken from here:
http://www.katsbits.com/smforum/index.php?topic=326.0
The upper and middle part of the test model is exported without errors. The problem occurs when I try to export the bottom part (l_legs). The contents of the error below:
Traceback (most recent call last):
  File "C:\Users\...\Blender\2.76\scripts\addons\io_export_md3.py", line 792, in execute
    save_md3(settings)
  File "C:\Users\...\Blender\2.76\scripts\addons\io_export_md3.py", line 745, in save_md3
    md3.Save(file)
  File "C:\Users\...\Blender\2.76\scripts\addons\io_export_md3.py", line 404, in Save
    s.Save(file)
  File "C:\Users\...\Blender\2.76\scripts\addons\io_export_md3.py", line 258, in Save
    v.Save(file)
  File "C:\Users\...\Blender\2.76\scripts\addons\io_export_md3.py", line 109, in Save
    data = struct.pack(self.binaryFormat, tmpData[0], tmpData[1], tmpData[2], tmpData[3])
struct.error: short format requires SHRT_MIN <= number <= SHRT_MAX

location: <unknown location>:-1

I have only basic knowledge of Phyton and I can't understand what is wrong.
The test model is here

I've been experimenting with the model and found the cause of the error. The size of the entire model must not exceed the dimensions 1000 x 1000 units

authors: Александр Дубинин


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How to remove one of the group inputs
I'm using Blender 2.74 and trying to follow an online video tutorial on creating "sun" (presenter is using version 2.63). The problem I'm facing is that the presenter just selected a few nodes in the Nodes Editor and pressed Ctrl + G to group those nodes. Then he pressed TAB to edit the group and remove some of the input sockets of the GroupInput node by clicking the cross button in front of those sockets. Now I do not see these cross buttons in my version of Blender. I tried using Properties window too (N key) but that also doesn't allow removing (although it does allow adding, renaming and reordering). Can anyone help me with this?

Figured it out at last. Select the group input node and press N key to bring up Properties window. You can then use the cross button next to the node label that appears immediately below the inputs and outputs list. Here's a snapshot:

In the Shader Editor view, select the group node and enter Edit Group mode. Open the right side panel with N
In the first tab, called Group, you can access the inputs. Highlight the one you want to delete and press the - button to remove it.

For Blender 2.92:
I pressed N and it brought the options and there's the Node Wrangler (you'll have to enable this plugin. Then press the node of the interest - in my example it's Material Output, and then press Frame Selected. And it's out. However I didn't find how to remove that frame about it, but that's good enough for me.

In Blender 3.2 I found this not far away: press N and choose Group instead of View.


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Add a group instance with python
I have a group of objects named MyGroup. I can add a group instance with  Shift+A -> Group Instance -> MyGroup, but I can't figure out how to do it from python scripting.
I'd like to add an instance of MyGroup, calling it by it's name from a script on python.
Something like the bpy.ops.mesh.primitive_plane_add() operation, but instead of adding a plane, i want to add a group instance.
Is there any way I can do this? all I could find about groups was this http://www.blender.org/api/blender_python_api_2_74_release/bpy.ops.group.html but it does not speak about adding group instances.

I had the exact same question yesterday ! It is indeed hard to find examples.

I know it sounds illogical but if you were looking for adding a group instance, you'd have found it under bpy.ops.object: http://www.blender.org/api/blender_python_api_2_74_release/bpy.ops.object.html

This creates instances of the group, it works by first adding an Empty, and setting its .dupli_type and .dupli_group attributes. I believe for all intents this is functionally equivalent to a group instance.
import bpy

scene = bpy.context.scene

group = bpy.data.groups['CubeGroup']
instance = bpy.data.objects.new('dupli_group', None)
instance.dupli_type = 'GROUP'
instance.dupli_group = group
scene.objects.link(instance)

(credit to: blenderartists.org user Atom)
For completeness, this is how to create groups via the API. This expects the name (string) of a group, and will add any objects in the objs collection to this group.
def to_group(named, objs):
    '''
    named:   (string) name of group to use, or to create if not present
    objs:    a collection of object references
    '''
    groups = bpy.data.groups

    # alias existing group, or generate new group and alias that
    group = groups.get(named, groups.new(named))

    for obj in objs:
        if obj.name not in group.objects:
            group.objects.link(obj)

How counter intuitive !! I would never have found these dupli_ attributes. At least that works perfectly. Thanks !

yeah, me either. it's a maze sometimes.

I think zeffii is close to the right answer but I can't get it to work. Meanwhile I found on the Blender documentation page an operator that works if invoked properly. I wish to avoid using operators but here you go. Let's say you have a group called my_group, adding an instance to the scene works with this:
bpy.ops.object.group_instance_add(
    name='my_group', group='my_group', view_align=False,
    location=(0.0, 0.0, 0.0),
    rotation=(0.0, 0.0, 0.0),
    layers=(True, False, False, False, False,
            False, False, False, False, False,
            False, False, False, False, False,
            False, False, False, False, False)
    )

Please note that name and group parameters require the same value (here 'my_group') so that this works.

it didn't work for me, it says that can't find the keyword name... maybe we are using different versions of blender? (sorry! my bad! forgot to say that I'm using v2.63), maybe you should put your version of blender in your answer, just for completeness ;). Btw, why did you add so many Falses at the end?

This worked on Blender 2.74. I think I have version 2.64 somewhere so I'll give it a try.


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How to make a physics simulation permanent
I have a bed of pebbles that have been physics simulated and are now in a resting position:

I want to append this to an architectural render I'm working on. When appending, the pebbles go back to their start position (suspended in space).
I don't want to bake the simulation, because it's only the ending position I care about. Is there a way to apply all the pebble's positions?

Create you RigidBody simulation
Choose the desire frame
Select your objects,
perform Bake to Keyframes (hit F3 for the search menu and type bake)
Change the frame range to the frame selected. If you leave the default, i.e. multiple frames, it create keyframes for all.

ALTERNATIVE:

step to the desired frame,
Apply Visual Transform followed by
either Remove Rigid Bodies or Remove Rigid Body World

The menu item Bake to Keyframes does not appear when I search (prob because I had already baked, which doesn't work when linking across files). Nevertheless, you gave me the idea to try Remove Rigidbody World (at the desired keyframe), and it worked!
If you edit your answer to explain how to get the menu item, or amend it to include my solution, I'll be glad to mark it as accepted.

Roger that thank you

That said, removing the RigidBody World did not work for me. Even after baking the cache. It simply reverts to the original position.

After a few tests, I can confirm that stepping to the desired location and doing Apply Visual Transform followed by either Remove Rigid Bodies or Remove Rigid Body World will work.

First off, go to the target frame and make sure only your pebbles are selected.
In the 3D Viewport, under Object > Rigid Body select Apply Transformation. This will make the current position the pebbles' starting one.

Then, in the same submenu, click Remove to remove the pebbles from the Rigid Body simulations; that is, to make them simple, static meshes again.

I did try this solution, but the frames are animated as before. Will this work with clones of objects (all my pebbles are three different copies that share the same mesh and material)?

I'm conflicted, because when I tried your answer, the Remove option did not appear. However, in a new file, it does, and your solution works. So, you solution did not solve my problem, but it does work. However, because of everyone's input, I was able to find a way, so I'm marking this one as correct.

Select the object and press CTRL + A > Apply visual transform

Tried your solution, and it says that because my objects are multi-user, transforms cannot be applied (for all transforms). Apply visual transform does nothing in my case.

Are you sure you actually select Apply Visual Transform and not any other apply option?

I believe you are correct. Apply Object Transform doesn't work, but Apply Visual Transform does (though it doesn't help). However, your solution does work if followed by Remove Rigid Bodies.

Create the simulation
step to the desired frame
In the 3D Viewport, under Object > convert to > Mesh from Curve/Meta/Surf/Text

This create the copy from the simulation

(Blender 2.92) Make sure to select "keep original" after step 3 in the pop-up dialog in the 3d viewport if you want to retain a copy of your objects with simulation applied.


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How to get the image textures around for eyes, eyelashes, and eyebrows when exporting a human model from MakeHuman
I have been struggling with this simple but naughty problem since a while now. I can do good things in Blender, but I miss simple knowledge, so I'm sure someone can help easily.
Once I have exported a .mhx model from MakeHuman into blender, the textures are not ready for cycles. I can quite easily add the skin by just following these simple steps:

In Object Mode, select the body, go in Material > Surface and click "Use Nodes"
Replace "Color" with "Image Texture"
Select "Young_light...diffuse.png" or whatever the default image is.

Everything works and goes on as planned:

But when I repeat the same steps for the eyebrows, eyes, and eyelashes, everything turns black instead of using the image texture. Arrg! I tried Ctrl + N to invert the normals, but that doesn't fix anything. The same problem persists in Cycles view. Would anyone please help me here? Thx!

I had the same problem for a while but solved all 3... I hope the following helps you...
as you can see this is the end result...

The first thing to do is to select each object and make sure the UV's are aligned correctly...
To do this, split the 3D view (I assume you know how to do this) and change the new panel into a UV/image editor, then, select the eyes and with your mouse cursor over the 3D view port, tab into edit mode and press "A" to select all verts...
If you don't see them appear in the UV window then you need to unwrap them (You can find the Unwrap command in the tool shelf of the 3D view port).
I tend to unwrap them anyway just to make sure blender registers the UV maps.
If you do this then I found you will need to re-align the UV's manually so keep that in mind.
You should see them appear in the UV/image editor.
Once you have them aligned go to the UV/image editor panel, look at the bottom edge, just passed the menu options you should see a place to load or link an image.
Click the small page with an image icon to link existing images or load the image texture from wherever it is saved on the disk.
It should already be aligned. Tab out of edit mode and you should be done with the eyes.
Do the same for the eyelashes and eyebrows.
Okay so that's step one out of the way, onto step two...
the same nodes work for all 3 Objects(eyes, brows and lashes), they are as follows;

All you need to do is change the textures it uses for each one...
Please vote this up if it helped because it would lift some of the restrictions I have, so I can help others out...
Thank you everyone!
P.S. I have only got this to work with cycles renderer, as of yet I have not got this working with the Blender render engine but am determined and am working hard at it!

Thanks for the answer. I'll come back to you when I try.


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Boolean - subtract multiple objects from one with only one boolean modifier
Is there a way to subtract multiple objects from one using single boolean modifier? For example I have a wall, and I need to make multiple holes in it for windows. I wanted to parent an object that will make a hole in the wall to a window object, so wherever I move the window, the hole will be made automatically, and if I duplicate the window, the object that is it's child will be duplicated too, and will generate holes too. Thanks in advance.

The boolean modifier only works with one object, but that object could have multiple separate meshes. So you can either join all your windows into one object, or add additional boolean modifiers to achieve this.

but best results if you do it one by one, boolean is prone to errors

Subtracting multiple objects from another object with just a single "boolean" modifier is possible in Blender 2.91:

Create a new collection: Right-click inside the object list in the upper right - "New collection"
Move all the objects that you want to subtract into this collection
Create a new boolean modifier for the original object
As "Operand Type" choose "Collection" instead of "Object" from the drop-down menu
Pick the collection in the "Collection" field underneath
Continue as you usually would

Step 4 and applying the modifier can take quite a while, depending on how many objects there are and how many vertices they have, so I wouldn't recommend doing it this way if complex objects are involved. Instead rather subtract the objects one by one or group only a few of them together.

No, you can't input multiple objects into a single boolean modifier.
You can add as many boolean modifiers as you want though. Simply create multiple boolean modifiers with their respective object's input.
You can also join all objects into a single object and use that as the boolean input. E.g. you could duplicate your window, then merge it into the boolean input object by ⇧ Shift RMB selecting the input object (making it active) and pressing ⎈ CtrlJ to join them.
As you intend to speed up the process, I'd advise you to use the built-in BoolTools addon, which creates a shelf for assign boolean quickly.


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Calling a function on duplicating
I am wondering if it is possible to call a Python function inside a Blender when an object with a name that starts with foo_ gets duplicated? Thanks in advance.

You are probably looking for this: http://blender.stackexchange.com/a/19669/7777 You just need to watch the number of objects inside a scene with this watcher.

I saw that answer, it would work, but i am new in python, so as I understand all i need to change is add_watcher() line, but how to watch the change in number of objects in scene?


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Moving the 'center of the object' to the actual center...
I have sculpted a model in sculptris (maybe i have done something wrong, it's my first time) and exported it to an object then reduced polygones and stuff, and now i have some stuff to do in blender but i noticed that the center of my model isn't really the center. It has moved to his left and idk how to move it to the right position. I have never used Blender before so maybe it's a dumb question. Here's an image of what it looks like:

I'm not a Blender guru so please be as precise as you can if you know how to fix this.Thank you for your.

Changing the Center is easily done with the moster of a shortcut Ctrl + Shift + Alt + C.From the dropdown select

Origin to geometry If you want to move the center.
Geometry to origin If you want to move the mesh.

If you want finer grade control of the position of the center, you can go to Edit mode by hitting Tab, select all vertices by hitting  A and move the mesh with the widgets. The center doesn't move, so you can position the mesh onto the center like this.
In Object Mode you can center an object so that the center is at the center of the scene (by moving the mesh) with the hotkey Alt + G.
I hope this helps.


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Make strength of emmision independent from the surface brightness

How can I make that sphere glow less but still keep the luminance. I've tried to mess around with the options but without results.

I assume you are using cycles, is that correct?

If it is cycles, you simply need the light path node, use the is camera ray option

I have no clue what you are saying about cycles.

http://imgur.com/hfBD0dU

Here you can see my settings. I also have other settings on the World tab

Related: http://blender.stackexchange.com/questions/42803/how-to-make-mesh-lights-brighter-without-washing-out-in-the-render/

Okay i changed the render mode to Cycles , but now i lost all colour. Please help. This looks cool

Yeah, Cycles can't use the same materials as BI, so Cycles just defaults to a flat gray material. You could use Cycles, but you'd have to remake all your materials. It's not hard, but you'd have to learn Cycles.

Look into filmic Blender as well: https://www.youtube.com/watch?v=m9AT7H4GGrA

With the Blender Internal renderer, it's not very easy, but it is doable.
The basic idea is to render the glowing ball twice, and composite the dimmer one over the brighter one.
Keep everything you have so far, but investigate how to render just the ball. The basics are, move it to its own layer and set up a second set of render layers that gives you only the ball, with nothing else in the scene at all.
More on Render Layers from the Manual:

Each Render Layer has an associated set of Scene Layers. Objects which are on one of the associated Scene Layers are shown in that Render Layer, as long as that Scene Layer is also visible.
Warning
Only the objects in visible Scene Layers will be rendered. So, if only Scene Layer 1 is visible and your Render Layer set specifies to render only Layers 2 and 3, nothing will be rendered.

Once you have those two renders happening at the same time, you will use the compositor to put the dimmer ball (that's all by itself) over top of the image that has everything in it. You'll use an Alpha Over node to combine the two.
More on the Alpha Over node in the Manual:

Use this node to layer images on top of one another. Alpha Over does not work on the colors of an image.

Doing this with Cycles is much simpler, but Cycles does not use the same materials as BI. You will have to make your materials again, as Cycles materials. That's why everything doesn't have any color when you just change renderers. Cycles is using a default gray material.

I might have another answer and one that takes only a minute or so to put in place.
Just place a "Point"lamp inside the sphere and parent it to the sphere.
Wind up the lamp's strength if need be, and make the sphere's surface as dull and as dark as you like.
I've got the lamp's strength wound up a bit to exaggerate the effect.
Adjust the cube's (and surrounds) specular to whatever colour and reflectivity is required.
Please note - this was rendered using 'OpenGL'.  The noise (banding) you see on the cube occurs after the gif animation and compression, not Blender's video.


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Video editor Speed Control adds extra frames?
I've got a small clip (that is a chunk broken off from a larger clip), say 32 frames that I want to run at 1/2 the speed in the video editor. I apply the speed control effect to it, check the box with "stretch to input strip length" and then change the strip length to 64. However, when I play the clip it plays the original 32 frames normally, and then just added 32 more frames from the larger clip the smaller one came frome.
How do I make the original 32 frames run at 1/2 speed and not just add more frames from the original source? Am I doing something totally wrong here or maybe a missed setting?
Thanks in advance for the help

Use the Multiply or Speed Factor setting. This stretching doesn't work reliably, I had this problem before...

Thanks, yeah seems to work without that bug when stretching is not selected.

It may be that you have to press the Refresh Sequencer button (at the bottom of the VSE timeline window) to make the Stretch Effect work correctly.


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Blender UV Edge Artifact
the first image is of my mesh with all faces selected, and the corresponding uvs. The shader effect I want is a simple gradient based on the uv y-coordinate (for export to unity).

The second and third images are in blender and unity, respectively, showing an artifact where the edge is brighter than the interior of the faces. Both fragment shaders (in blender and unity) only return uv.y * color so the edges should not be brighter than the face interiors.

What could be causing these bright edges? There is no lighting in either of these scenes, and the shaders do not use the normals or lighting at all, just returning (uv.y * color). As the error appears also in the unity view, I know it is a problem with the input uv's, and is not some random blender view display setting.
I did notice that when I select "UV Sync Selection" extra points appear in the UV coordinate grid, and I cannot select these points individual - they appear to be tied to faces. Is this causing some issue somehow? I am not sure what these apparently extra vertices are. The image below shows the same UV layout, with the "UV Sync Selection" toggled on.

In any case, thank you for your time and any suggestions.

Did you apply the scale to your object and UV unwrap it?

I did apply all transforms, including scale. I unwrapped it and set the uv's for each vertex to (0,y) where y is their appropriate height. Maybe I am treating the uvs too much like just some input data and I need to change my unwrapping process?

A UV map is a flat surface. There's no concept of 'height' on the map itself. It just has X and Y coordinates for 'width' and 'length'. Suggest you watch a few UV unwrapping and texturing videos! This is the Blender manual introduction to UV unwrapping.

for the height, I remap the height of each vertex to the range of [0,1] so if my object has vertices from (x,0,z) to (x,10,z) and a vertex is located at (x,7,z) I would make the uv coordinate (0,0.7) - this way the relative object height is saved in the uv data so I can make a shader that makes a vertical gradient. I am not going to use any textures. I will read through the blender documentation - thank you for the link.


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Does 3D printing with Blender only print faces?
So I'm pretty new to the whole 3D printing thing, and I was just wondering if only the faces will print when I use Blender to print a 3D model.
For example, if I take a basic cube from the template and print it, would a hollow cube be printed or a "solid" cube.

I'd say this belongs to http://3dprinting.stackexchange.com as this is a general question about 3d printing .Partially related - http://3dprinting.stackexchange.com/questions/953/can-a-sandstone-3d-print-be-printed-as-a-solid-object.

Just as a quick addition, 3D printing only prints closed coherent manifold shapes, and unless the software used for printing provides any automatic shelling facilities it should print as a solid filled out object by default. If you need to add thickness to it I suggest manually modeling the inner shell yourself. The Solidify modifier may be a good starting point for simpler shapes and uniform thickness. For more complex stuff and internal support structures I'm afraid only manual modeling will do.

Mr. Zak is right that you'll get better answers on the 3dPrinting.SE, but the answer is that it will print a solid cube. Printing starts at one face, and continues until it finds another face (sort of). So if you only have one face, it knows where the material starts, but it doesn't know where the material stops. If you wanted a hollow cube, you'd have to specify a width for those walls by creating an inner cube with normals pointing toward the center of the object. The printer can't (won't) assume how thick a zero-thickness polygon should be.
It's useful to remember that all 3D polygons only have 1 face. This can be confusing, because there's nothing in the real world that works this way. That's why a single face is considered "non-manifold."
Duarte's answer includes the same information, but the terminology might not be familiar to you. A closed, coherent, manifold shape is one that is:

closed: all edges of all faces are shared by 1 and only 1 other face, like the default cube.
coherent: (essentially) it that has dimensions that can exist in the real world. Intersecting geometry, or geometry that has zero width is not coherent.
manifold: (basically) geometry that has one distinct "inside" and one distinct "outside." More specifically, all the normals are pointing the same direction. With the default cube, you have normals on the outside, and they are all pointing outside.

If you were to do this:

You would have an interior face, with a normal that is neither pointing inside... nor pointing outside. Thus, this is non-manifold geometry.
For a more thorough a technical discussion of non-manifold geometry, see the answer to this question.


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Getting pixel rgb values of background image in blender
I need to know the blender python script to read rgb colour values on a background image on screen (the image used as aid in 3d modelling) or just to read rgb values from whatever is rendered on screen at a specific x,y position, assuming the background image is included. The aim is to create a script that auto-positions mesh vertices according to the bg image as if modelling from bg image but automatically.

Some useful links, get pixel coord of view http://blender.stackexchange.com/questions/7106/get-location-in-scene-for-pixel?rq=1  get the rgb value of a pixel http://blender.stackexchange.com/questions/53780/pixel-coordinates-of-image-with-python?rq=1


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Matcap material in Cycles
How to recreate this selected matcap material in Cycles? It's most glossy in the center and has this special coat.

To recreate this matcap try to use some Layer Weight nodes. Experiment with the Color Ramp node's modes and slider's placement also.

Here's my nodes setup. I basically added two Emission shaders- one with the white color and the other one with black color. Then used the Layer Weight (Facing) (with different Blend values) and Color Ramp (with different modes- Constant for the bright rim and B-Spline for the blurry interior of the sphere ) nodes.

Here's the test I've done using my low poly gerbil model. The matcap and the render result look almost the same. It is a matter of tweaking some things. If you want to play with the nodes to make the rendered matcap material look perfect here's the .blend:


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How to make array of group ?
When you made a group of objects, how to make array of them?
I know for shift+A to make group instance but I want to control it like array modifier.

Perhaps of help: http://blender.stackexchange.com/questions/2525/array-a-group-of-objects

Well, I think it is duplicate.


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Spiral texture/material on the sphere
How to setup material with a texture on the sphere which will look like this

I have draw in Paint straight line but I don't know how to bend it spirally around the sphere with material nodes. Also, I don't know how to make transparent background with this line.

I don't think there is any simple way to do it with this texture. But there is a blender addon that makes spirals. See http://blender.stackexchange.com/questions/5755/model-a-simple-3d-spiral-shape, but change the spiral type in the operator panel

Thank you but I don't want the mesh. I want to make spiral texture on the sphere. I thought there is procedural way with the line.  Is it possible to bake mesh spiral onto sphere as a texture?

If the spiral does not have to be mathematically perfect, you can draw it in Tintaur app (iPad/iPhone) and then export textures for use in Blender. It will be a long sequence of linked arcs, start from one pole and add points circularly steadily going towards the opposite pole. After that export the textures (top right button) and replace background color with transparency in some 2D picture editor.


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Grease pencil conversion
I can't convert GP into mesh or curve.
There are tools options to convert but nothing happens.
I was following old tutorial but now is something different.

Assuming you use standard conversion (no BSurfaces) - are you sure it wasn't actually converted ? Grease Pencil strokes remain visible after conversion and overlay the curve which is thin, so uncheck visiblity for GP layer and see in Outliner / 3D view if curve appeared.

I can't select curve with right click so I think it's not there or it's not created .

It still isn't clear.. Can you make a short gif of the process ? In the animation please include viewport with the Toolshelf opened, Outliner and no more than 1-2 objects in the scene. You could also upload the file before the conversion.

Ok, I figure it out. I have been in edit mode so conversion was greyed out. When I switched in object mode, I could make conversion.


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Hair particles and collision
I've set cube with hair particles. Cube is slightly above the plane. How to make that hair particles collide with the lower plane.
Like they are bumping into plane but not going through the plane.

I think you can't, as the manual says: "Hair particles ignore deflecting objects (but you can animate them as softbodies which take deflection into account)." - https://www.blender.org/manual/physics/collision.html

How to connect softbody physics to hair particles? I tried with to attach soft body to emmiter but that didn't do anything.

I didn't know but searched a bit on the web: one way to make hair to collide with a mesh as you wish is to enable collisions on the mesh, increase "outer" setting, and then animate between  two keyframes (for the mesh). It's slow, but works. Let me know if you need a detailed answer. See https://www.youtube.com/watch?v=27XzJGGlibs


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Inserting random loop on the mesh to change topology
How to insert random loop on the mesh ? It doesn't need to be circular.
I know how to use Crtl+R but I need to add more complex curve/loop streching to many faces.
Is it possible to draw the loop with grease pencil and then just attach it to mesh topology ?

You can't change the topology of the model using the edge loop tool alone as CTRL R uses the existing topology of your model. Instead try using the knife tool to manually create your own topology.
Documentation for this can be found here.
https://www.blender.org/manual/modeling/meshes/editing/subdividing/knife_subdivide.html
Make sure that when you use the knives tool you correct your topology as you are going as this can create ngons in areas that can be troublesome.

Link is broken.


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Animation in edit mode
Is it possible to animate faces and edges in edit mode ?
For example, set a keyframe for face location and animate it till translated under z-axis 10 units, etc.
Similar question with edges.

As an alternative to @Patdog's solution: you can use shape keys to set individual mesh/vertex locations and then keyframe the influence value.

To set a keyframe, go to your starting frame, move your mouse over the value parameter and press "I" to set a keyframe. Go to your next frame, move the value and press "I" again while over the value to set the next keyframe.

Is it possible to animate using armature in edit mode? So, bone would handle one face rotations or translations?

I dont really understand the question. Could you explain a bit more what you are trying to accomplish?

If you want to rotate/translate the particular faces of the mesh but not all. So, some faces rotate around it's origin and come to their own original location on the mesh.

You cannot animate directly in Edit Mode but you can make hooks that allow animation via Object Mode. You can do the same for edges. The hotkey is CTRLH

Off-topic, but how did you bring up that mode wheel? The one that gave you options like Object mode, Vertex Paint, etc.

It's the Pie-menu addon which comes with Blender - just have to tick it. Find it very helpful :)


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Bool tool brush question
After using bool tool,brush boolean difference,
how to make brush object stay for another difference bool?
Now, when I apply brush boolean difference, brush object is gone.

If you make the brush object active after Difference brush was added and apply it only for the brush it will remain undeleted, just its Maximum Draw Type will be set to Bounds (it will return to Textured once Difference brush is removed from the object). However the final effect of the brush will be applied to the canvas.


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Sharp tip in texture mode
When I go in texture mode, there is soft circle to paint with.
Is it possible to paint with sharp lines like squares and circles with sharp edges?
I mean sharp edges when there is no soft gradient between black and white texture.

Circle brush
You can use Curve to change your tip sharpness. There are six presets for them and you can make your own as well.
Curve types:

Square brush
The best way to have square tip or any other shape is to prepare one in 2D software (Krita, Gimp, InkScape, Adobe etc.)
Make tip shape white and transparent background (for convenience sake) make it pretty big for good quality (4k in my example) and save it as PNG with Transparency then setup Texture Mask as below:

Blend file (square tip texture packed)


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Driving Hair from a Texture
I want to grow grass (hair particle system) driving by a texture instead of by a weight paint (because vertices are not accurate enough for my purposes).
According to my understanding, this should be possible using the Vertex Weight Edit modifier, as seen in Vertex group from texture. However, the .blend file included in that response does not even work, and I am unable to figure out how to set this up.

As an example, I want to grow grass in the white areas, and have no grass in the black areas.
Here is the .blend file I set up so far:

A sleepless night brought up the following question: How to add a Particle Texture?
The steps are finicky but work well:

Create the particle system, and create/paint a new texture; include it as the object texture if you want to see what you're doing (the object's texture/material won't affect the particle system).
In the Particle Properties tab there's a dropdown called Textures. Select your texture.
In the Texture Properties tab, go under the Image > Settings dropdown and select your image (again).
At the very top of the Texture Properties tab, set the dropdown to ParticleSettings - Texture.
Finally, under Influence (still in Texture Properties), check Density to let the image drive particle density.

Also, for the particles to appear at the right place on a non-square surface, it may be necessary to select the UV unwrap for the particle system to match the texture placement. That's under Texture Properties > Mapping > Coordinates, select UV.
Steps 3 and 4 are particularly strange at first, but work well after all. Tabbing in/out of edit mode will reflect the particle system changes. Then, to texture paint the hair, go to texture paint mode and paint more white on the texture, remembering to tab in/out of texture paint mode to update the particle system.

WOW THANKS!
Blender team made this way so UN-OBVIOUS. Now I can use image map for hair density instead of vertexes!
https://i.imgur.com/VEUeySU.jpeg


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Wait for compositor to finish before saving image to file - Python Scripting
I'm trying to write a script that will tweak some settings in the compositor, then save the resulting image.
However, The resulting image is NOT receiving the changes that are being made in the compositor. I suspect that blender is not, "waiting for the compositor to finish" before saving the image.
I've tried using Application handlers, but I don't really understand how to use them in this case.
Any help? Here's the code in question, without attempting to use application handlers:
        #get the render result
        render = bpy.data.images["Render Result"]

        #set the value of a compositor node to 0
        bpy.data.scenes["Scene"].node_tree.nodes["color vs. depth"].inputs[0].default_value = 0
        #change the colorspace to filmic
        bpy.context.scene.view_settings.view_transform = 'Filmic'

        #save the image
        render.save_render(filepath = tool.my_path + tool.my_string + " COLOR.png")

it might be much easier to create a file output node in the compositor instead, this will anyways save the frame when you trigger a render

You can check if the compositor is processing with bpy.app.is_job_running.
You do have to delay your script a little bit because the compositor process doesn't start until your script finishes. You can use bpy.app.timers.
import bpy

render = bpy.data.images["Render Result"]

bpy.data.scenes["Scene"].node_tree.nodes["color vs. depth"].inputs[0].default_value = 0
bpy.context.scene.view_settings.view_transform = 'Filmic'

def wait_for_compositing_and_save():
    if bpy.app.is_job_running("COMPOSITE"):
        return 0.01  # Try again in 0.01 seconds
    render.save_render(filepath = tool.my_path + tool.my_string + " COLOR.png")

bpy.app.timers.register(wait_for_compositing_and_save, first_interval=0.01)

This worked! Thank you so much!


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Random UV rotation
When I unwrap the model, how to procedurally rotate UV faces so that the texture does not appear seamless ?
I now need to rotate every UV element separately. I would like to do it in one go. Is it possible to do it ?

If I understand you correctly, switch your Pivot Point to Individual Origins and then R to rotate them around their centers.

This may be it but can I rotate  faces in random direction?  With this method every face is rotating in the same direction.

As far as I know, there's no simple, built-in way of doing that.  You can do random proportional editing but it really messes up the symmetry of the islands.  One thing you can do is enable Island selection mode, select half of the quads, rotate them, Ctrl+I to invert the selection, and rotate them the other way.  Not random, but gives you more disparity.

Also, in your 3D View, you can Checker Select faces when doing UV mapping.

You may try R key along with the angle value
eg. R 90 or R 180
If you wish to rotate the individual box than you may combine above keys, with setting Pivot Point to Individual Origins


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How to paint alpha emissive mask ?
I would like to have my material on the object.
Then I want to paint an alpha mask which will be an emission texture material on top of my material.
Basically, only part of the object which will emit light will be my painted texture on it.
How to do that ?

First of all, you are going to want to UV unwrap your cube by going into edit mode and using something like "Smart UV Project." If you then go into the "UV / Image Editor" panel, you should see your faces outlined. Go ahead and hit the new button next to the +, and leave the color as black. Click OK and select paint mode from the drop down bar next to the button with a picture of a pin on it. You can now drag while clicking to paint over your texture. When you are done, select "Image > Save as Image" and name and save your texture. If you don't, the texture will be gone when you reopen the blend file. Your texture should look something like this:

Now, go back into your "Node Editor" panel, and add a new emission shader, mix shader, and Image Texture. Connect the your base, non-glowing material to the top "shader" input of the mix shader, the emission shader to the bottom "shader" input, and your Image Texture "Color" to the "Fac" input. Finally, in the Image Texture node, select the texture you drew on earlier. What this does is, in the white areas of your texture, the emission is able to show through, whereas the black areas let the base shader show through. Here's a picture of how it should all have come together:

In the end, your result should look something like this:
Have fun Blendering! Cheers,
Graves Broderick

Don't mention it! One last thing I forgot to mention, make sure after you paint your texture to select "Image > Save as Image" inside of the "UV / Image Editor" panel. If you don't the texture will be gone when you reopen  the file.

Ok, thanks. When in paint mode, what is the difference between blend input: mix, add ...?

Yes, I didn't save the texture and it's lost when you open it.

I'm sorry I didn't tell you it would be gone sooner, you'll have to redo your texture. I wasn't quite sure if I was remembering how it worked correctly when I typed that. Here's a list of the different blend modes you were wondering about.  Basically "mix" lays your new color over the top of the color underneath, and "add" actually mixes two colors together (like red and blue making purple).


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Bool tool and shading
After booling with difference there is left weird shading on cube. How to fix it?

http://www.mediafire.com/file/hutki3noraf0ksg/bt.blend

It's because there are some ngons created by Bool Tools. Add more loop cuts to the mesh and use autosmooth. Or just model it by hand, it will be very simple (keep only quads).

2 Ways you can fix it
Click the Cube and go to shading in the left hand tool panel instead of smooth just click Flat

OR
Click on the cube and apply the boolean modifier only and add the edge split modifier to it. And bring the edge split modifier on the top then the bevel modifier in the order.

In both ways bevel is gone.

on click of flat shading how the bevel is removed its applied the flat shading nothing else and the bevel is at the outer side not inside of the cube

Yeah, bevel without smooth shading.

and notice there is no bevel inside u have to add bevel

In OP example there are both inside and outside bevels. Still those methods are bad habits because of 'dirty' mesh topology.


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UV unwrap spiral texture
I would like to have spiral shape texture on the cylinder. How to UV map the model and how to make a texture which wraps around the cylinder ?

First, unwrap your cylinder -- Edit Mode; Select all (A); Unwrap (U) -- with a cylindrical projection. Use a texture that joins the top and the bottom seamlessly.

Then select the bottom row in the UV window (B and make a rectangle) and shear it by grabbing to a side (G).
Voilà.


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Blender dev build question
On https://builder.blender.org/download/ there are 2 version available for download:
non-stable build and
Experimental Build Branch by VS 2015 .
What does this mean and what are the differences ?

A build considered as not stable is a version in developpement. They have new functionnalities/changes that still need to be tested, or contains known bug that will be fixed before official releases.
An Experimental Build Branch, as said in the description are build with another compiler than the "usual" one. They should be stable (release 2.78) but you never now what can appen using a compiler that wasn't used for tests.
If you have no reason to use one of them, use the official release


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Groups from scene to scene
How to send group of objects from scene 1 to scene 2 ?
I have group in scene 1 which I would like to use in scene 2.

select all group objects, then make link to the scene 2?

If you want to add a group instance in another scene just do so from the Add menu with Shift+A > Group Instance > Group name.
If you want to move objects themselves between scenes use method of copying and pasting or linking.


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How to smooth area with sharp edges?
I´m quite new to Blender and this is what I have achieved so far:

Now I want to print a little model of this helmet. Unfortunately there are a lot of sharp edge areas like this one here:

Is there any way I can get rid of them without editing every single edge by hand?

When adding screenshots consider to crop them to the actual area of it (white areas). As to object, those likely caused by how the mesh was constructed (topology). There isn't one-solution, try checking non-manifold geometry, removing doubles, and may be uploading your file.

The Subdivision surface object modifier
There are two things that I've identified in your screenshots that need to be improved. One is a fix, and one is the modifier.
Mesh Topology
Tab into Edit Mode and key A once or twice until everything is selected. Key Alt + J to convert Tris to Quads (triangular faces to quad faces). You can also key Ctrl + F to open the Faces menu and manually select Tris to Quads. Lastly, you can go 3D Viewport > bottom menu > Mesh > Faces > Tris to Quads.
Ctrl + F menu:

Mesh > Faces menu:

Subdivision surface
The Math
This will use the Catmull-Clark algorithm to create new faces between two imaginary points in the center of each current face.
From Wikipedia:

Catmull–Clark surfaces are defined recursively, using the following refinement scheme:
Start with a mesh of an arbitrary polyhedron. All the vertices in this mesh shall be called original points.

For each face, add a face point.

Set each face point to be the average of all original points for the respective face.

For each edge, add an edge point.

Set each edge point to be the average of the two neighbouring face points and its two original endpoints.
For each face point, add an edge for every edge of the face, connecting the face point to each edge point for the face.

For each original point P, take the average F of all n (recently created) face points for faces touching P, and take the average R of all n edge midpoints for (original) edges touching P, where each edge midpoint is the average of its two endpoint vertices (not to be confused with new "edge points" above). Move each original point to the point:

       This is the barycenter of P, R and F with respective weights (n − 3), 2 and 1.

Connect each new vertex point to the new edge points of all original edges incident on the original vertex.
Define new faces as enclosed by edges.

The Modifier
Go to the Properties panel > Object modifiers tab and add a Subdivision surface modifier. The two values you should care about are the View: and the Render: values. The View: value determines the number of subsurf levels, or iterations, displayed in the 3D Viewport. The Render: value determines the number of subsurf levels in a rendered image or animation. The Render: value should generally be higher.
The Subdivision surface modifier:

Subsurf levels 0, 1, 2, and 3 on a Suzanne:

authors: Шыңғыс Мұхтаров


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How to join a camera to an object?
I'm modeling a phone and need to have a camera positioned where the phone camera is, when I try to join the camera and object it fails with a message telling me the camera doesn't have any mesh data. And all my google searching just brings up how to make a camera track an object which to be clear is not what I am after - I need to simulate the constant position and rotation of the front camera on a phone with respect to the LCD display when the entire phone is moved.

Did you tried with parenting the camera to the object?

Thanks Carlo, so making the camera parent and then locking the camera's transform achieved what I want. If you would care to turn your comment in to an Answer I would be happy to accept it as 'The Answer'

Parenting the camera to the object will solve this problem. You can do this by selecting the camera first, and then selecting the object you want to parent it to. You can parent by pressing CtrlP, and then selecting object (keep transform). This should fix the problem.

Select the objects and keep camera as the active object, then press Ctrl + P to do parenting.


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What would prevent me from selecting verticies of active object in edit mode? (v2.82 is it a bug or my ineptness)
I had been modelling a part by applying a mirror modifier to a box and doing extrusions and such without problems. The problem appeared shortly after adding a sphere object inside edit mode and moving that into place so the two surfaces intersect... Now the project is in some state that no matter what I do I cannot select vertices anywhere within the object in edit mode even after restarting blender.

Overlays were disabled. Click on the overlay button to make selection and other things reappear.

Thank you and +1 for animating the answer.


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How to achieve a 3D warp field effect in blender (2.81)
I'm after a way to create an effect such that when an object is placed inside the volume the verticies are displaced based on the localised field value (thinking of it like a density field in physics where the local distance between atoms decreases as density value of a region increases)?
The current model I would like to use it on is spiral column that I need to gradually flare out at the top and displace randomly along its length in order to create a solid tornado funnel - but I'm sure I could come up with lots of uses once I know how to do it.

Vertex Proximity Weight might do what you are looking for https://blender.stackexchange.com/questions/153177/worms-crawling-under-skin/153181#153181 https://blender.stackexchange.com/questions/165827/using-a-b%C3%A9zier-curve-to-raise-lower-height-of-vertices/165831#165831

Is this the effect your are looking for? https://blender.stackexchange.com/questions/84438/squeezing-shape-by-another-one/84460#84460

While the proximity weight modifier looks very interesting it wasn't exactly what I wanted - but while looking at other answers to the suggested questions I found the Lattice Modifier which is pretty much exactly what I was thinking of just by a different name.

Thanks to the comments I finally found out about the Lattice modifier system which when you take away the physics speak is exactly what I was thinking of when I posted the original question - below is a proof of concept 'Tornado Susan' using the stock Susan model with a lattice modifier applied to flare the top and give the length a bit of a flick
And the Lattice Modifier that was applied is shown below which takes no time using proportional editing


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how can i Attach both hands to the same object (gun's main grip and front grip)?
i already attached the right hand's bone to the weapon's main grip (using select weapon > ctrl+p > to bone ),
now i want the left hand (with the same holding position) to keep automatically following the weapon's front grip. what should i do ?

You have to make a seperate bones and on the wrist use the copy transforms constraint. Place the Seperate bone at the foregrip , apply the constraint to the wrist and the should follow , You will need to tweak the position of the bone , but it will work.


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Can I import animations into other blender files?
I want to know if I can create an animation in a separate Blender file, and put it into another file so I don't have to worry about the scenery in my Animation. Thanks!


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how to texture an object and keeping the object's color
I'm trying to to texture an sample object to produce an object with "color" and texture.It work in blender render..
but not in blender game.
I wish someone can help me with this for my game.I'm new with blender :P thank you]3

This is because you're in solid view. change to GLSL (N, Sahding, GLSL) And then click the texture button at the bottom of the screen (Z) and change to textures (the sphere with checkers.)


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How to bridge edge loops with a twist of .5?
I'm trying to make a 3D model of a twist-cut torus, like this one:
https://youtu.be/3_VydFQmtZ8?t=3m39s
The current version of the model costs about $50 in Shapeways.
I'm trying to get that down by cutting both of the half-tori into two hollow pieces, so 4 pieces total. Then I would make them tight fitting so I can assemble it later.

The problem is that the 'Bridge Edge Loops' -tool pairs the vertices up wrong,

and I can't cut the tori straight:

How would I go about making this possible?

The bridge tool has a twist option in the redo panel (F6 right after running the operator) which offsets the vertex pairings. Is that what you are looking for?

See http://blender.stackexchange.com/q/1972/599

I was using 12 minor segments, and it didn't help if I twisted the bridge. But now using 10 segments it seems to work with no twists. Quite strange.

It just so happens I modeled a Mobius strip a little while back, and I'm sure the technique I used can address your case as well.

Model a plane, or some variation of a plane. Best to keep it simple at first.
Place an Empty at the end of your object. Actually, it should be a little further from the end of your object, but we'll adjust it later.
Select the Empty, then the mesh object.
In Edit Mode, with the end vertices selected, Hook those verts to the Empty Ctrl + H (Hook to Selected Object).
Add an Array Modifier to your plane/mesh object. Choose Object Offset and point it to the Empty. Set the Count to 3 or 4 iterations so you can see the effect.
Now in Object Mode rotate that Empty and you'll see that mesh twist like a DNA double-helix.
This will probably need some fine-tuning, so in Edit Mode with those same end verts selected you can un-hook the verts (also Ctrl + H]). Then move the Empty and re-hook the verts. You can play with it until the positioning is right. It's hard to describe this part, but if you try it you'll get it.
Finally, you should have a strip that you can twist and stretch using the Empty.
Once you've twisted the strip to the degree suitable for your design, save your file, then apply the modifiers.
Place your 3D cursor where the center of your ring will be and align your view accordingly, then use the classic warp tool - Mesh > Transform > Warp to wrap your mesh into a ring shape. Remove Doubles.

Another way to to this would be to use the Curve Modifier, but it won't give you an evenly incremented twist like this technique does.

For anyone creating a (Mobius strip like) twist where the normals oppose each other where they meet, there is the additional challenge of how to merge these, which I will briefly address. Here, the vertices at the edge where the normals are opposite have been ripped with pressing V.

Halving the Solidify Modifier's Thickness value, then duplicating the object and making the value negative on the duplicate is one way to fix this. Then you can apply the Modifiers, join the two objects, and merge the vertices at the seam. After that, additional clean-up of of the mesh, such as the deletion of internal faces may also be necessary.

Once the two objects have been joined, and vertices welded, here is the final result:

Two .blend files for reference:
http://www.pasteall.org/blend/36552
http://www.pasteall.org/blend/36553

I did this shape other way. Hope it would be interesting at least for practice.

Create section from two semi-circles (for example: delete half of circle, connect ends of arc, move a bit from center, duplicate and place appropriately);
Extrude up and use Cut Ring with proper number of cuts, like 3*n-1;
Create Bezier Circle about 3-4 times larger first circle (using scale);
Put Curve modifier on mesh, switch in modifier axis to Z (if you created shape in XY plane by default);
Switch to top view and scale bezier circle slowly until you get your mesh exact 3/4 of turn
First vertex in bezier circle is where mesh starts, direction is pretty understandable, so select second vertex and assign tilt to 900 (Transform panel, at right side of 3D View), third to 1800, and fourth to 2700;
Apply Curve modifier;
In Edit Mode delete first (of 3) quarter of mesh, then select all mesh and duplicate it rotationg around global Z and cursor (hope you are doing everything around cursor and 0,0,0), and remove duplicate vertices;
PROFIT.

The trick with 3/4 was done just because I didn't find how to divide bezier loop in vertex without loosing shape.


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how to enable GPU option in user preferences
i was searching online tips to speed up the time of rendering, and i've found one screenshot which is like this
but in my case there is no option of GPU in the compute device section, have a look at my screenshot

am i missing any hardware ?

i am using linux and the link given says everything related to windows, so can anyone help me now please

and i have AMD hardware


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Create videos with loops and breaks
I would like to create a video that will be used in place of a usual powerpoint presentation. For this I need that the video automatically stops a some predefined points or that some regions are looped until I press "play" on the player.
With the DVD format this can be done in a very contrived way (correct me if I'm wrong).
Is there a way to produce those videos with Blender? Are there other formats that support these features?
Thank you

I doubt it.. Blender's video editing capabilities are pretty basic. You are most likely better off using an external program to set up the DVD formatting (using footage from blender or wherever). Note that I have never fiddled with DVD formats before, so I might be wrong.

No, Blender's VSE can only output a single linear video file. Any stop points, or looped sections would need to be provided during playback with the whatever player or app is consuming the video file.

I think the OP is thinking about menus, chapters, and loop points, which are all things DVDs are capable of (according to wikipedia).

@gandalf3 Yes, I was asking exactly that: is it possible to generate DVD "metadata" using blender? Other video formats are welcome.

@MarcoM If blender doesn't support this (I'd be surprised if it did), you might try one of these.

It is possible to create interactive movie playback using the blender game engine.
The complexity required will vary greatly depending upon the needs of your project.
To provide some ideas, I dug up a couple of tutorials that look at interactive movies and game cut scenes. An understanding of the game engine will be required however.
https://www.youtube.com/watch?v=6PV5dAzgtzA
https://www.youtube.com/watch?v=P2W_fQayYcA


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Prevent point lamp from shining through mesh lamp in reflection
I have a scene which must appear as if it's lit by a very small mesh lamp.  To optimize performance, what I'm trying to do is place a point lamp inside of the mesh lamp, and have the point lamp shine through the mesh lamp by having the mesh lamp's back faces be transparent.  However, in the reflection of the lamp on a glossy material, the point lamp shines through the mesh lamp:

I've tried making the point lamp invisible to glossy surfaces via Ray Visibility, and having the mesh lamp only be visible to glossy surfaces and the camera.  While this works, it makes rough glossy surfaces quite noisy, partially defeating the purpose of using a point lamp instead of a mesh lamp in the first place:

Are there any other solutions?
.blend file

Why don't you simply use the sphere with no lamp ?

@lemon Small mesh lights are extremely noisy.

I figured it out, with help from @lemon.
What I needed to do was prevent the mesh lamp from casting shadows, by either:

Having a simple emission shader (no trickery in the material whatsoever, just an Emission node connected directly to the Output node) as the mesh lamp's material, but also disabling shadow ray visibility on the mesh lamp.
Using this node setup on the mesh lamp:

Two possibilities:

Remove the glossy ray visibility of the lamp :

Or you can set up the sphere nodes like this :

OK, this is what you said in your question... but it works...


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What's this camera viewport/clipping visualization for and how do I get rid of it?
In Wireframe and Solid view modes, there's this "cone" of visibility that extends out from one of the cameras and clips all the objects in the scene:

It does not move at all when I switch cameras or move the camera. I've tried clearing the camera border but it had no effect.
It doesn't appear in Material Preview or Rendered modes.
How did this show up, and how can I make it go away?

This might be because you accidentally used the shortcut Alt+B (Viewport clipping?) while trying to define the camera border.
The solution it that case is to press Alt+B once again in 3D viewport mode.


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Different vertex coloring behavior depending on vertices painted
I've been experimenting with vertex colors on the default cube. I've painted three vertices, as is visible in the picture:

My question is, why does the upper right face visible in the picture form a stripe where opposite vertices are colored, while the the other two visible faces are colored differently?
It seems that in any given quad, coloring the top left and bottom right vertices will form a stripe in the middle, and the other two vertices will color in the other parts. My assumption is that this is because each quad is really two triangles, and the coloring is more greatly "stretched" along the longer side, creating the stripe in the middle. Is this correct?

you can check this is due to the inner triangles of the quad faces : enter edit mode, select all and press ctrl+T

Indeed, this is due to the triangles which make up the quads. The 45° angles, two of which make up two of the corners of the quad, receive vertex coloring differently than the 90° angle. Basically, the corners made of two 45° angles get twice the amount of coloring.

Subdivide each face in Edit Mode.
This will solve your problem, since it adds another vertice between the two corner vertices


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Strange UV Unwrapping Problems (n-gons?)
I have this sort of drum/cylinder with spoke-like things supporting it from an inner cylinder. The part I'm having trouble with is the inner cylinder, from which the spokes protrude. I've separated the UVs for the spokes from the inner cylinder, but when I UV unwrap the cylinder UVs look horrid. I won't bore you with details, because the attached blend will probably make more sense anyway, but here's the problem, as shown when the UV and mesh selections are in sync:

I've already checked for and removed some non-manifold geometry but as this obviously isn't an organic shape it wouldn't be likely anyway. Some of the segments of this cylinder are semi-OK and can fairly easily be fixed by manipulating the UVs, but my question is "why?". Also, I'd prefer to stick to traditional UV mapping with seams et al. rather than "Smart" UV Mapping (I've tried it and the rest of my mesh doesn't unwrap as well then). Thanks in advance!

With that section selected rotate the view until you are looking straight at it and use unwrap->Project from view

Oh, thank you! It worked great with orthographic projection!


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Change Transparency Value of an Object in BGE with Keyboard
In the Blender Game Engine, I have a cube as a window and have set it's Z Transparency value to .200. I would like to add Keyboard Sensor where when I hit a specific key in-game, G for example, it would change the transparency value of the cube to 1.0, like a solid wall. I would also like this to work in reverse as well, where if I hit G a second time, the transparency value would return back to it's original .200. I'm sure there's a simple solution to this that I am overlooking but any help would be appreciated, thank you!

Transparency animation

Go to first frame (1). Mouse cursor over Material/Transparency/Alpha I. The Alpha field will turn yellow.

go to last frame (21). The Alpha field should be green right now.
enter 1.0

Mouse cursor over Material/Transparency/Alpha I.The Alpha field will turn yellow.

Go back to frame 1 again.
Your material action is prepared. You can play the material action the same way as any other action. Here is one option:
Logic
Add an action actuator

setup start frame (1)
setup end frame (21)
setup action name (MaterialAction)
setup playback mode (Flipper)

Add a property

"opaque"
type: boolean

logic to toggle opaque
Keyboard sensor -> AND -> Property Actuator Toggle "opaque"

logic to play animation
Property Sensor Equal "opaque" True -> AND -> Action Actuator

I hope it helps


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How to detect collision amongst concentric circles
In my shooting gallery game, i have a bulls-eye formed from concentric rings (each a separate object). It seems like for any collision bounds i use, the bounds for the outer rings cover the inner rings. Hence, when i hit the center ring, all rings sense a collision since the outer rings collision bounds overlap the center rings.
Any ideas on how to handle this?

try the "Triangle mesh" collision type.

Add a single collision mesh for the entire board, then calculate the distance to the centre to determine which ring was hit.

To get holes in a collision mesh, you need to use triangle mesh bounds.
Otherwise it will always assume the mesh is convex (which is faster to calculate).


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Adding Thickness to a 3D Textured Plane in Blender
I created a 3D textured plane in Blender and I want to increase the thickness so that I can 3D print it. So, I just need to basically extrude it so that in stead of a rectangular plane, I will have a cube/rectangle (three dimensional) with the 3D texture on one face.

who not just use the displace modifier to create the texture on the subdivided plane, and then use solidify to add thickness?

Use the displace modifier on your plane, setting the texture to your aforementioned texture. You'll need to have enough vertices on the plane for this to work - if it's still just a 4-vertex plane, either subdivide everything multiple times in Edit mode or add a higher Subdivision Surfaces modifier before the Displace modifier. Play around with the setting until your texture is elevating itself nicely out of the plane without crashing your computer (or your 3D printing company's limits).
Then in edit mode select all the vertices down (E key) and after extrusion scale all of them to end on the same height so they form a flat surface to make your box.