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Rendering a large number of unique objects
I've got a script which imports a bunch of hi-resolution models onto a grid. It gives me this:

It's currently got 35 objects (81924 vertices per object), but I'd like to rotate the camera toward the horizon, and arrange many many more objects out to infinity (~1500 of them).
I feel that a simple extension of what I'm doing now is going to run my machine out of memory. And since I only really need hi-res data close to the camera, it's a waste of resources out at the horizon.
What would be a good strategy for rendering many hi-res models in a single scene?

Are you instancing them? (dupli objects?)

do you really need 81924 vertices per object? You could add a decimate modifier to each of them and apply it. That can bring the poly count down a lot.

@gandalf3 the brains look unique

@gandalf3 yeah, the brains are all different

@vader I suppose I'd just have to experiment to find a good decimate ratio based on distance from the camera?

@ajwood You could try a driver.

@ajwood You could check out the level of detail script because when your far distant hires models are rendered using only a few pixel in the image you actually don't need a detailed model see 2nd part of my answer here: http://blender.stackexchange.com/questions/7301/automatically-picking-high-poly-low-poly-model-based-on-distance-to-camera

I would just decimate all of them to a rather low level. Or you could just pick a few ~20 brains and instance them, could you get away with this?

I'd keep some hi-res models close to the camera, then have a decimated copy that uses two array modifiers to fill the background. You could even bake a normal map to use on a very low poly shape for the background.

as it stands right now OP would end up at about 30 million polygons, probably more though.

Does instancing reduce render time? I've never heard about that until now, but if so, it's good to know. Is this also true for BI or just Cycles?

both support instancing. THe main improvement form instancing is the reduced ram load, with instances you can have virtually unlimited duplicates. Any speed increases gained might be side effects.

Would it be possible to split the brains into multiple scenes or layers and combine them using the compositor?

one brain is enough for me.

Instancing does not really help if each brain is an unique mesh.

Have you also made sure to remove doubles (duplicate/ very closely spaced vertices) from those models? It could cut down on vertices which would allow you to instance more parent models for the render.

You could group all the brains (Ctrl-G) and then use the brain group in a particle system on a grid which emits from each vertex. Make sure the number of vertices = number of particles. Also be sure to display your models as bounds only, otherwise Blender will try to draw all the detail in viewport. Using a particle system allows me to draw forests of complex trees, so I think brains should work too.
In the picture you see the group of objects in the front and the result of a particle system on a subdivided grid emitting from each vertex in the background.

I think the problem is loading 1500 unique brains into memory, this method works fine with a small number of unique items

But I don't see why you would need 1500 unique brains. As long as those in the foreground are unique and those beyond that a random selection of the foreground brains, the observer really won't notice the repetition. Heck even on these unique brains it's pretty hard to see.

Looking closer I think I already see duplicates, second row, 3rd, 4th column.
3rd row, 4th and 5th column.

I think in OPs image there are duplicates because OP cannot render even a few unique brains. I agree there only need to be a few unique in the render

15 unique brains of 81924 vertices is about 1.2 million vertices. I think that shouldn't be a problem for even a moderate computer. Lets hope OP weighs in on the matter.

I think the problem is that OP want to do a fly through It might be somewhat obvious that there are a bunch of clones.

Sorry I've been MIA. My first step is going to be getting a render with lots of detail close to the camera, and random clones far away. But Vader is right that I'd like to be able to fly through to show off all of the uniqueness.

@David, you're right that there are duplicates here.. kind of an accident.

My motivation for making this image is to show off a huge number of unique brains, so I want to avoid obvious clones.

David, this is a good solution for the case where it's OK to make copies (which may be most cases), but I use Blender for scientific visualizations, and the animations must perfectly represent my data, or else the result would be similar to fabricating data.  I have also ran into memory problems importing my models into Blender, so I'm looking forward to seeing some more answers.

Then the only thing I can think of it cutting the scene up into bits with the maximum amount of models you can run. Then rendering the same flightpath over each scene and compositing them.


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Copy Physics To Multiple Objects
Using the cell fracture addon, I created many objects from my mesh. I want to have a rigid body physics on all of them. How would I copy one of the fractured pieces physics to all the pieces? I tired ctrl L and the copy attributes addon, but none of them have the option. Any help is great.

do any of the objects have physics properties? Or are all of them plain meshes that need them? Or do you have an object with physics properties that you wish everyone had as well?

If you have one object that has physics properties and you wish that the other object had the same properties:

Select all object that you wish to copy the physics properties to
Select the object you wish to copy the physics properties from

note: We select this one last so that It becomes the active selected object. This is the object that has the desired physics properties.

Then In the Physics panel under Object Tools choose Copy From Active.

If none of them have physics properties than you will want to add them:

Select all objects that need physics properties.
Physics -> Add Active

I can't seem to find the rigid body tools. Could you post a screenshot of your whole desktop?

one sec. I will. What version of blender are you using?

I am using 2.69

@user2593789 The tabs will be introduced in 2.7, but you find all the items in the left panel.

Thanks, that works to copy the settings. It doesn't work if I want to actually add a rigid body physics to multiple objects. any way to do that?

select them all: Add Active, I will update answer

Hi, since 2.8, isn't there any other shortcut than just the F3 search menu ?

If you only want to copy single properties, you can right click on the property which you want to copy and select Copy To Selected:

This will copy the value of that setting from the active object (the object with the yellow outline, usually the last selected) to any selected objects (objects with an orange outline).
Note that this works for non-physics settings too.

This is really a useful and potentially more powerful feature than the chosen answer.  Up-vote for usefulness.

For 2.8# series you can copy items from either the search menu Copy Rigid Body Settings

or from the 3D View Menu Object > Rigid Body > Copy From Active

You can also just select all your objects, then on the last one you select, add the physics property you want them all to have, then press Ctrl+L and select modifiers.

In 2.81a on Windows, I had to add all objects I wanted to simulate into a collection, set physics on one object, then RMB the collection, choose "select objects" and then in 3d window CTRL+L and select Collection. It works!
Edit I was NOT using Cell Fracture add-on. I was using many blocks via Mesh>Extras>Wall Factory from the Add Mesh: Extra Objects add-on.
I just tested this method with Cell Fracture add-on and the same method works; you still have to add to a collection and link collection in order to distribute physics data of an object to the rest of the objects in that collection.
You can also link modifiers like Bevel for a nicer look for your bricks.

Separate test with Cell Fracture add-on. Had to add Suzanne's parts to a separate collection, set physics of one object, select all objects in collection, CTRL+L to  link to collection and then physics were applied!

source: Stack Exchange

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

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Problem with white edges
I want to composite a cube over a background while still keeping the alpha channel for the cube. I want the composited image to be a cube over an image. The alpha channel should be only the cube. I would like to use the alpha channel as a mask for further compositing. The problem is that with my current node setup there is a border around the cube.
blend file

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


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3d Manipulator not working
I am working on building a model car. I found that the manipulators won't work. The X, Y, Z axis don't do anything except move my 3D Cursor to where I clicked. I tried the Translation manipulator, Rotation manipulator, and the Scale manipulator. Is there anyway I can fix these manipulators so that they can work again?

@Comrade Vader I didn't see any issue with the wording there.

Sounds like a left-click/right-click issue. When I have my preferences set to selecting with left-click, right-click will only move the 3D cursor as you describe.

Well left click moves the 3D cursor like it does in 2.70 and 2.71 version of blender. Right click for me selects the object and moves it wherever without any axis constraints. I attempted to research and found that switching the mouse buttons the other way around didn't do the trick. Any other way?

You can also use G R and S, see http://blender.stackexchange.com/a/6395/599

@gandalf3 Is that 2.72b though? I don't think that question is focused on Blender 2.72b. My quest is about 2.72b and need to really know how to fix these manipulators.

@7Blue_Beast7 AFAIK nothing with the manipulator has changed recently, so everything in that answer should apply to 2.72b. If it still doesn't help, try reloading the default setup by pressing File > Load factory settings.

@gandalf3 I tried and nothing works but ima go ahead and re-install blender.

Reinstalling did nothing @gandalf3

@RayMairlot So how do I enables my transformation widgets to respond upon click?

@7Blue_Beast7 You shouldn't have to do anything. Are you sure you are left clicking? (sorry, but it should just work..)

@7Blue_Beast7 If all else fails you can always try submitting a bug report, see: http://blender.stackexchange.com/questions/1377/best-place-to-put-bug-reports

I solved the problem thanks to Blender.org


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Blender Image compression from command line
I am running blender from command line and using some scripts.In order to reduce the output size, I'd like compress the .png output file.I understand that this can be done in Blender GUI. However, I am struggling to find a way of doing it in command line or in script file.

bpy.data.scenes["Scene"].render.image_settings.compression = 15

Welcome to the site :) Perhaps you could add some detail on how this works and how it can be used from the command line? (also it might be better to use bpy.context, otherwise it won't work if the OP's scene isn't named Scene)

You would have to put this in either a text block, or a .py file, and use the -P command line flag to have Blender run this script before exporting the animation.

I embedded Blender in a python script to create a movie out of pictures. Maybe you may want to take a look at the code


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"Cannot execute boolean operation"
As you can see from my image, I am trying to subtract the mesh "Subtract" from the mesh "Cube"

However blender is giving me the error "Cannot execute boolean operation"
What is causing this problem?

can you upload your blend file?  http://www.pasteall.org/

wasnt too sure where to upload it so i put it on mega: https://mega.co.nz/#!gEZnCBxD!9onl-J0HoJTRNGqq4V6wrAkfdfhorYdCVAVzQ0EOZH0

Is that cube 2D?

@user3789776 do you want to join the two objects into one?

It looks like blender has trouble performing boolean operation on meshes with large ngons. There is a very easy workaround for this problem.

Select the face that will hold the window

This single polygon has 8 vertices, more than 4 vertices is considered an ngon

Triangulate it by pressing Ctrl + T, this will make many triangles out of the big ngon
(optional step) With the polygons still selected, you can reduce the number of triangles by converting tris to quads by pressing Alt + J.

Final Result

Worked perfectly! Will this fix most occurrences of this issue?

Yes, if not all.


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Prevent meshes from clipping into each other
There are two meshes that are clipping into each other.

I used the boolean modifier to subtract the cylinder from the wall object. How do I fix this problem?
.blend file

If you could upload your blend file here I could take a look at it. Also you can upload your image directly to the question. Or if you don't the file host imgur is preferred.

If you are referring to what can be seen in the image below, this is called z-fighting. It is when to surfaces overlap and are in the same 3d space. This is not physically possible in the real world.

To fix this you would have to get rid of one of the overlapping surfaces.

Select the object Cube
Select the faces that are overlapping.

Delete them, x -> Faces

Final Result

Comrade's answer is good. If you want to keep both meshes intact, there is an alternative way.

Select the Cylinder.001 object
Scale the object by hitting s
Scale it down by an appropriate amount. You can try .99 to start. Keep adding 9's until you see z-fighting happening again. If so, hit the backspace to erase the last digit.


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Blender Cycles: Diffuse only lamp
I'm trying to create a cycles lamp shader that only lights up the diffuse component of the materials around it. Kinda like having its Glossy component turned off in the Ray Visibility box under the object tab. But it is not working. I seem to be missing something quite basic.
Here's my node setup:

When the material is reflecting sharply (with roughness turned down to zero), the node setup works. But with blurry reflections, it stops working. What is it that I'm doing wrong?

It seems to me that this might be a bug caused by multiple importance sampling. If you disable it (for the mesh light), it works as expected (the floor is a 50% mix of glossy and diffuse):

Unfortunately, this makes it extremely slow to converge..

I think it might be the node setup for the light. When I set up a similar scene with a pure emission shader on the plane, everything worked as I think you wanted.

In the scene I have a plane with a 50/50 blue diffuse/white gloss mixed shader, a 100% green diffuse shader and a 100% red glossy shader all at about .2-.3 roughness. There is also the default amount of light being emitted by the world
Finally just to prove that the red glossy plane isn't reflecting the light, I turned off the world light and you can see that the red plane is no longer being lit by any light source and is completely black.

Hope this helps you.

But that wasn't my question. I had set up the light's shader in a way that it'll it'll light up only the diffuse and transmission component of any shader. As in, when a camera ray cast by the camera hits the glossy surface, and the point of impact subsequently shooting a "glossy ray" into the lamp, that ray will only see a purely transparent material. But it doesn't seem to work that way.

After some experiments, I find that my setup works when the reflecting surface is 100% reflective. But as I increase the roughness of the surface, the lamp shader's effect decreases.
I'm supposing that when I keep increasing the roughness, the glossy material starts resembling a diffuse material (and since my lamp set up affects only the glossy component), and it gradually stops working.

But all this is plain supposition and I've no idea how blender handles these things under the hood ( this understanding, I'm sure, will clear my doubts. Certainly (: )

Oh I'm sorry, I misread your question. I thought you said turning off ray visibility wasn't working. My bad :( Is your floor plane an entirely glossy shader?

Hi drent, yes the floor is completely glossy. So by theory, the lamp should have no effect on it. But it doesn't seem to be working that way. I wonder what is it that I am missing.


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Boolean Modifier Trouble
I'm having trouble with the Boolean difference modifier. It isn't cutting out some pieces of the mesh:

With the difference mesh hidden (note the lack of the rectangular cutouts)

All the normals are in order:

The modifier is not showing any errors or warnings.
Paste all .blend link
In addition to any potential solutions I'm also interested in the description of situations when it happens and an explanation of the cause.

You can fix this problem by first triangulating the mesh you wish to carve holes into. The large ngons on the top and the bottom make it hard for blender to create these holes.

Go into Edit Mode, Tab
Select the mesh you wish triangulate, A or hover mouse of mesh and press L
Triangulate the mesh, CtrlT

You will notice that the error message under the modifier is now gone.

I did not get the error message in the first place.

@Michal, that's what I get when I open your blend file. What version of blender are you using?

2.67b. I'll try upgrading to the latest version

@Michal that would be a good idea.

Wow, upgrading eliminated the need for the problem as 2.72 has a good DXF importer! Triangulating indeed fixed the issue

Blender was throwing exceptions, you just have to check the System Console by going to Info > Window > Toggle System Console. To get rid of the exceptions I just selected the rectangles and separated them into another object. Then I applied the Boolean modifier for the cylinders, then added and applied one for the rectangles. This gives me this result:

I'm looking for a way to automate this. In general if I separate by loose parts, add a modifier for each seperated part the problem persists

@Michal You have to apply the first modifier, then the second. This works for me


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How to create a animated silhouette?
I am making an intro for 'The Tim Show'. The thing is I've only modeled a good head and that's mainly it.
The intro will be like shadows of a person, with a drill in a hand, etc. Look here at 1:07 on the earth. Here is an image of it:
(I do not want a globe/sphere, only on a screen)
But it will be with Blender (yes!!) and will not be on an earth. I may enhance it with some other stuff.
The thing is I don't know where to start and I need a fast solution as I am under pressure.
Thanks in advance

What about an animated texture?

By mainly a head, that is the thing I have ever done in Blender (that head is not in the intro)

how long is the clip supposed to be?

@JebediahKerman: As long as the beginning of this: http://revision3.com/tbhs/double-decker-3d-printer-part1

You can use a human mesh with a shrinkwrap modifier on a plane. Let me show you an exemple:
First if you want to use an human body you can create it with makehuman and import it in blender with all the skeleton. Then you can create the animation of your human.

After that you can add the surface where you want your silhouette to be. For the exemple I used a plane.

Now you can add the shrinkwrap modifier on your human.

Now it's time to render. I've done the render with cycle, in blender internal you have problem with the superposition of the mesh like this:
So here is the final render with cycle:

Here is the video example on youtube.
And of course it works with animation. Hope this can help you.

Thanks so much! WHat is the license for using makehuman? Thanks! I speak french too at home, I live in the UK!

@TimTimmy See their website.


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How can I "convert" a blender model into a 2d drawing?

As one can see, behind the "Koro" text, there is the outline of the lama.
How is this effect created? Are there any options in the compositor to do so?
How can I "convert" a blender model into a 2d logo?
Many thanks ;)
.blend file: https://mega.co.nz/#F!9QMGCTxL!PIc910mkaEhot_dlYFeQQg

Why not render it from the side? I'm afraid I don't really understand the question...

@gandalf3 Ok... How can I change the 3d object as a "2d shape", so that nothing sticks out, e.g. think of a drawing of a lama e.g.: http://imgs.steps.dragoart.com/how-to-draw-a-cartoon-llama-step-6_1_000000011669_5.jpg

For this case I think all you need is a shadeless material.

@gandalf3 If you won't mind, please post your response as an answer! Thanks ;)

If you want outlines like in the picture you linked, you could try using freestyle.

Another option is to use the Material Override option in Properties > Renderlayers to override all the materials with a flat gray shadeless material.
For example:

Create a shadeless gray material:

Use it as the renderlayer override:

Result:

Nice and clean solution, and fur looks awesome! How long did it take to render?

I chose this answer as it also included several screenshots, which is useful to locate the buttons, well-deserved!

@codemanx I don't remember exactly, but not long (I would estimate about a minute).

@gandalf3: thanks, just wondered, 'cause my Blender hung at "Preparing scene data" longer than your entire render time. Dunno what was wrong.

@CoDEmanX You could try disabling some things like AO and environment lighting in World settings, but other than that I guess it's just all that hair ;). BTW, I rendered again and the time is 1:06.61.

A very straight-forward solution:

Create a new material and pick a Diffuse color
Enable the Shading option Shadeless
Replace all materials by this new material(did not work for Koros eyes for some reason, I replaced them with UV spheres and assigned the shadeless material)
Disable the sky for rendering(I removed the entire node setup to get rid of it)
Switch Viewport Shading to Textured
Change to GLSL Material Mode in the N-panel Shading options
Change to ortho sideview (in this case Numpad 3, Numpad 5)
Render OpenGL and save image as PNG with alpha

Result (click for hi-res):

Note that it doesn't include simulated hair, but on the other side, render time was < 1 sec.

OMG all these answers are so good! I have no idea which to choose!

If you are going for a 2D logo at the start, I would recommend using curves. They're easier to manage (in certain ways) than a plane.

Add a Bezier Circle and change it's type to 2D in the shape settings:

Model your logo:

(Don't ask what this is supposed to be. I was going for a dinosaur thing, but it came out as more of a snake/cat thing)
Set your camera to orthographic and position it in front of your logo.

Remove your lights from the scene and set the material to shadeless. Pick whatever colors you want.
Add text (ShiftA > Add Text) pick a font in the object settings, give it a shadeless material.
Voilà:

I would +1 just because of "catlizard", but I don't think this really answers the OP's question of "How can I 'convert' [an existing] model into a 2d logo?". Still, useful info.

I agree with gandalf3, but I still upvoted your answer

Set the horizon color to white. Switch off all lights (including ambient occlusion). This will render a black outline, if you have a single object without background objects.


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Why can't I add sky nodes to a lamp in Blender Cycles?

I feel like my interface is missing the ability to add sky.
Although I have easily applied sky in another file before, no matter what I do in this file, the sky is black.
What went wrong?

The 'sky' is defined in the world : the little button next to the object (yellow cube and which look like... a world) of your screen capture. Here you are showing the object material nodes.

You cant add sky nodes to a lamp, you have to create a new World "material" and add nodes to it's setup, not the Sun lamp.
In the Properties Window go to the world tab (Fourth tab with a blue globe) and add a new one there if there isn't one already.
Then in the Node editor Window switch to World node type in bottom header, second button with the same blue globe icon.


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Need an effective simply way to enable Freestyle Line Edge detection
I have been working on an animation that involves some motion
of a number of mesh mode planes that have freestyle line edges on them.
There is a Freestyle Line Edge render detection issue, that I am aware of.
I am using the Blender Renderer.
I have had to use Visibility, QI Detection 0,0 in order to attain
the effect that I need. This means that I cannot use the
"always detect by default" modes.
My video absolutely must move through a relative acute angle
between the camera and the Marked Freestyle Line edges
of relevence.
I have read it suggested that there is a boolean variable solution.
I don't understand how to apply this, if it exists.
Certainly if I have lots, or too many, applicable planes
with their Freestyle Line Edges.
Aside from just "avoiding those acute angles",
or using an "always detect" mode for them, is there a way
to have those Freestyle Line Edges detected again?
I have posted the model file at
https://blenderartists.org/forum/showthread.php?448163-Freestyle-Line-Edge-and-Animation-problem&p=3299731#post3299731
as well as
https://blenderartists.org/forum/showthread.php?448209-Freestyle-Line-Edge-and-Animation-problem&p=3300012#post3300012

I must admit to not really understanding the question - does it come down to trying to make some edges ‘always freestyle regardless of angle’? If so, there is a Mark Freestyle Edge option in Edit mode and those can be enabled via the Edge Mark option in Freestyle Line Style. If it’s not that, please can you explain a bit more.

An illustration showing the difference from your desired result - i.e  which edges you are seeing that you don't want to see, and vice-versa, would help to define your problem.

If you do an f12 render and look at frames 410, 470, 480, 515, 565 and 575 you will see that there are certai line segments that are not detected.  Due to the requirement to work with with a QI(0,0) setting, I cannot specify Freestyle Line Edge settings any differently.  Does anyone know of a script, or some other setting, that I can easily use in order to have the missing Freestyle Line Edge segments appear?


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How to remove background colors in antialiasing pixels in Eevee?
I have a shadeless red material applied to the default cube.  The world background is green.  When the scene is rendered with Eevee, transparent green pixels appear at anti-aliasing pixels along the contours of the cube.  How I can remove the green color and make the anti-aliasing pixels purely red?  The green color seem to come from the world background.  No transparent green pixels if the same scene is rendered with Cycles.

Eevee questions are not on topic as 2.80 is not an official version.

have you tried increasing the samples?

Thanks for the suggestion.  I just tried increasing the number of samples.  It only affects the way how anti-aliasing patterns are generated, and the green background color is visible anyway.

Change the world background to a black color and it should look fine.
In this example I am using a world enviroment but wanted a color/alpha to appear for the camera/render.
At first the render came out with a light blue border over objects, and as I changed the "world bg" to black with the light path node, the render came out fine, without borders.
I hope this can be understood easily, im at work and typing this without thinking it too much


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Rotate instances to align with normals

Can anyone tell me how to get the pyramids to align with the normals of the deformed plane? I am using mesh to points so that I can target vertices, edges and faces.

you can do it with this node setup:

result:

UPDATE:
with your blend file, i could figure it out:
You inserted mesh to point nodes, which stop it from working, if you mute them, you get:

*** UPDATE ****
i found a better solution:
this node setup:

gets this result:

hey thanks for the answer, whilst this does indeed rotate the instances. In my example i'm targetting individual mesh components and I cannot see how to use your method with the mesh to points node. I've tried it with capture attribute also, just doesn't seem to have normal data.

Hi Neil, if you provide your blend file, I will help you. But without it I can only guess around.

that's very kind of you - https://pasteall.org/blend/ec19ac9c2baa4a868284ad1bb03e56b5

delete or mute your mesh to points nodes...then it works, i updated my answer

if I mute the mesh to points nodes, I will no longer have instances on faces and lines though

@Neil: i found a better solution. I update my answer. Hope you are happy now ;)

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


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Get vector position of single face from capture attribute node

I have a cone which is being positioned relative to the face which has points distributed on it. I want it to animate on the normal position of that face. The problem I had was that it always starts at the world origin regardless of which face I choose to use.
I tried to add a capture attribute node but this outputs a field, I have tried various ways to change this to a single vector so that I can position the cone in the centre of the face I choose via the index.
How would I modify my node tree to achieve this?

Try to plug "an Index selector" (just an Input/Constant/Integer node) in the "Sample Index" nodes following the "Distribute Points on Faces" node to specify the face you are targetting, instead of leaving the "Index" socket unplugged. I am running out of time for details right now, but could you have a look to this answer ? I think it might help you.

About the "red" link, I strongly recommend to read this post: Why is there a red line when I try to connect one node to another?

@StefLAncien thanks for helping me here, I have tried an integer in the Sample Index nodes but still doesn't work for me. Will this actually select a face as the Distribute Points on Faces node ouputs points not a mesh. Maybe i'm just not getting it.

Could you provide your Blender file using https://blend-exchange.com/ to give it a try ?

just add a set position node before or after (i am not totally sure which is right) and then plug in the end of the red line to the offset of that node. Then it should work. -> this only solves the "red line" problem, pls provide blend file

Would you like a single cone centred on  the selected face, or one cone per random point on the selected face, as proposed by Chris ?

@chris yes I want a single cone centred on the face I've chosen to scatter points over. Then I'm animating the cone so that it starts at the centre of selected face using the face normal direction. So i don't want it to go inside the mesh

(Using Blender 3.6.5)
Objective
To animate a single cone along the normal of a selected by index face.

Geometry Nodes graph

1. The targetted face is identified by its Index. For the demo, an Input/Constant/Integer node is used.
2. The face centre coordinates are recovered from the receiving geometry using a Sample Index node set in Face domain and linked to a Position node.
3. The face normal coordinates are recovered from the receiving geometry using an other Sample Index node set in Face domain and linked to a Normal node. This vector is converted to a rotation through an Align Euler to Vector node. Its Axis property is set to Z because the cone axis is aligned to Z axis.
4. The cone periodic displacement along the normal, between 0 and 1, is computed as:
$$ \frac{1}{2} \left\{ \sin{(\omega t)} + 1 \right\}$$
where $t$ is the frame count. With $\omega$ set to 0.15, the oscillation period is $2\pi/\omega=42$ frames.
5. The unitary displacement vector is computed by rotating the unit vector along the cone axis (i.e. Z axis) with a Vector Rotate node. (NB: the normal from step 3 could be used instead).
6. The position of the cone origin is computed by adding the scaled displacement to the face centre position.
7. A Transform Geometry node is used to specify the position and the orientation of the cone.
Resources

This does what I need and works with my setup also, thank you.

check this out:

result:

i separate the face as you did, then distribute faces on that face and then just instance cones on the points and adapt rotation via align euler to vector. Hope it helps.

As usual you were helpful, but I wanted the cone to be on a particular face which is why accepted a different answer.


text:
Apply material based on Y position of instances
In this experiment, I am instancing some icospheres on points of a torus geometry. I then use a simulation zone to move them on the positive Y axis each frame.
My intentions are to change the colour of the instances as they progress further on the Y axis, but I cannot figure out how to do this. Currently they get set a value from the colour ramp.
I would like each instance to change colour based on the gradient in the colour ramp as they get further from the instance torus object. Is this possible?
Here you can see the particles being generated from a torus object, I am moving the geometry up and down so the instances get generated on the z axis to give them an interesting look.

This is the node setup I have created to achieve this

And here is the material where I am using the posY attribute that I stored in the node tree.

first of all, connect y here instead of z and use float, not vector, because you wanna save only one value, not three.

and in the shader:

use the fac instead of vector, because there is coming only one value (y).
The colorramp expects a value from 0 to 1 ...but the y value is much bigger, so we have to divide that value so that we see the desired result.
result:


text:
How to rotate source video in Movie Clip Editor - Blender 2.68
After importing my footage in to the Movie Clip Editor, I find that it is not oriented the way I would like.

What is the easiest way to rotate this in Blender?

This video worked for me https://youtu.be/hfo-DRGvkgo

The guy has an updated version of how to do this in Blender 2.80 and up: https://www.youtube.com/watch?v=Wc6ZCjRZadk

You could add a transformation strip (effect) in the VSE and set the rotation. See the documentation for further details on available settings.

OK, but will this also rotate the movie that I see in Movie Clip Editor? As I need to add my track markers there.

@Neil You could try rendering the video out to a file from the VSE, then loading it into the movieclip editor. I don't know of any way to go directly from the VSE to the movie clip editor, but I don't use these much so I may just be missing something.

This seems to be the only way to do this IN blender, just need to remember to change the Resolution settings after rotation, this isn't done automatically.

The vse also has x and y flip states in strip properties. Better quality than a rotate effect. Would be nice if movie clip editor had this as well as the aspect ratio controls.

This dead link only answer is exactly why link only answers should always be removed. https://blender.stackexchange.com/help/referencing

@Rob I sure understand the whole link only thing (and I'm one that is constantly reminding people of it). However, in this case don't you think it was a bit overkill to flag it? You may or may not know that blender changed its manual, breaking all the links. This is normal, and pretty easy to fix the link. But aside from that, even without the link I still understood what to do. There was still an answer here; and that is the difference between a link only answer and an answer with a dead link.

@David Without the link, you're left with a picture. You can't search pictures so the answer is not discoverable. As one who is new to Blender, I don't understand much of the picture either so, to me, there is no answer here.

That is not quite all that is left. It says use a "transformation strip" and set it to "rotate" that is the answer. The picture just shows where the buttons are. Sorry to disappoint, but the manual is not going to be much more help here.

@Rob  If someone has the same question he will find the answer, searching for an answer you don't know doesn't make much sense. By the way  complains and critique is probably not the best way to join a community.

@David I see the rules for posting with images are not the same as Stackoverflow and other stackexchanges where such posting is restricted or prohibited. My concerns are valid for the same reasons other exchanges do not allow such posting but I would remove my flag if I could because, here, it's not against the rules.

Took me a while to figure out, but you may also need to rescale (I did). Ensure that your render output resolution is your desired output resolution first, then in "scale x" I put 1920/1080 and in "scale y" I put 1080/1920 and then the video's aspect ratio is correct (I was going from 1920x1080 input on its side to 1080x1920 output the correct way round)

The picture was enough information for me to figure out the answer.

Although its solved the problem, but in my  case it has a side effect, i.e. it reduce quality, so after a lot of search i end up with avidemux->Filter->Rorate 90 degree->save

In Blender 2.9

Select Video
Shift-A --> Effect Strip --> Transform

Strip Tab --> Rotation --> 90

To "Flip" the footage, use TRANSFORM --> MIRROR --> X & Y like so:

Transform footage mirroring X & Y turns it "right side" up:

This will only flip the source, not rotate it 90deg which is what I needed.


text:
Instance a plane on a cylinder using geometry nodes
Using a cylinder with a couple of loop cuts added

I just add a plane and then point instance this on the vertices of the cylinder. Can I make the planes attach to the faces instead of the vertices? How would you rotate the planes so they look like they are on the surface of the cylinder?

You need to use a Point Distribute node to instance on faces rather than vertices. The instanced geometry is automatically facing the face normal.

If you want to instance a plane on the center of each face, you can use a little trick with the Edge Split and Smooth modifiers.
Set the Edge split angle to 0° so all faces are disconnected, then use a low value around 1.1 for the Smooth factor. Increase the repeat until faces are really small. Add the GN modifier afterwards.

Using the Poisson Disk distribution on the Point Distribute node, set the Density to a very high value, and tweak the distance so only 1 plane is instanced on each face. It's best to tweak the distance first so as not to crash Blender with a gazillion instances :)

do you also know how this works without point distribute? because i never got this running...?

@Chris I think it's the only way to distribute points on faces... What part didn't work out ?

The rotation of the planes if you don‘t use the distributed points node

@Chris Try that https://i.sstatic.net/bsGai.png

you are my hero!!! works like a charm!!

Yikes. 1. a lot of jumping-through-hoops 2. Computational inefficiency. Grateful as we might be, GN has a long way to go, yet.

@RobinBetts my thoughts exactly, not intuitive to be using point distribute then basically hack things to get what you want. But its a great start and will only get better.


text:
Multiple scenes and material with pass index
I am trying to create the effect where something is bigger on the inside than on the outside, just like the Doctor Who's Tardis.
I have two scenes, one inside which is just some objects and one outside which has a box with one of the front faces that has a material index of 1.

As you can see, this renders just fine thanks to this node setup.

My problem is if I want to go inside the cube and appear in scene two, it just renders black, which makes me think its not going to the inside scene.
I only have one camera and have it linked to both scenes, I have a feeling its something to do with this, should I somehow have two cameras and link them together?
How do I transition from outside to inside without any issues?

Could you upload your .blend (e.g. to pasteall.org) and put the link here?

http://pasteall.org/blend/25432

This is because there is no thickness to the outside cube.
Your file is setup so that when the camera "sees" the face on the front it is replaced with the inside scene.
However, when the camera goes inside the cube, the camera can no longer "see" that face, so nothing is replaced with the inside scene:

Solution:
One way to fix this is to make the outside cube have an inside, by giving it some thickness. The easiest way to do that is with a Solidify modifier:

Delete the inset face on the front of the cube.

Add a solidify modifier in Properties > Modifiers > Add Modifier:

Now assign the door material to the inside faces:

Apply the Solidify modifier.

Select the inside faces and assign the "door" material to them:

Now your setup should work.
Frame 60 looks like this:

Yes of course this makes sense now, and has given me even more ideas, good work.


text:
Understanding 3D transforms and rotations
I am aware that a 3-D linear transform (combination of: stretch, shear, rotation) takes the form of a 3x3 matrix.
Also that if the transform is required to also handle translations, then one can either use 3x3 matrix + translation vector, or 4x4 matrix
However, I'm also aware that there is a different technique for handling rotations: to use quaternions, which looks like a 4x4 matrix (but does it behave in the same way?).
So my question is: how do these objects play with one another?
Say I start up my default Blender scene with a cube and a camera.

Now that transform panel is confusing to me. As it stands in that picture, I can imagine blender is using either 3x3 matrix + translation vector, or 4x4 matrix
But then there is a 'Rotation Order' pulldown which allows quaternions.
Can anyone explain what blender does behind the scenes?
The reason for my asking is that I'm attempting a script that transforms an object into camera space (i.e. If you were to transform the scene so that the camera is at the origin pointing downwards, wherever the object ends up, this is the location I use)
def main(context, num):
    bpy.ops.scene.new(type='FULL_COPY')
    cloneScene = bpy.context.scene
    cloneScene.name = 'clone'

    camera = cloneScene.camera

    for ob in cloneScene.objects:
        if ob.type == "MESH":
            me = ob.data

            # WorldToCam( ObToWorld( ObCoord ) )
            world2cam = camera.matrix_world.inverted()
            ob2world = ob.matrix_world

            obj2cam = world2cam * ob2world

            bm = bmesh.new()
            bm.from_mesh(me)

            bm.transform(obj2cam)

            for v in bm.verts:
                v.co = MyTransform(v.co)

            cam2obj = obj2cam.inverted()
            bm.transform(cam2obj)

            # save back into orig mesh
            bm.to_mesh(me)

And so I would like to have a clear understanding of what is happening when I apply a transform.
Although I've tested that this method works in simple cases, it looks like it might fall over when dealing with translations and quaternions (seeing as I'm inverting the matrix not the transform, I'm not sure if these are guaranteed to be the same. In a straight linear transformation they are...)
EDIT:
http://www.essentialmath.com/GDC2013/GDC13_quaternions_final.pdf <-- amazing walkthrough!
ftp://ftp.cs.indiana.edu/pub/hanson/Siggraph01QuatCourse/vqr.pdf <-- starts good, lost me with the links
courses.cms.caltech.edu/cs171/quatut.pdf <-- Ken Shoemake Quaternions

http://en.wikipedia.org/wiki/Quaternions_and_spatial_rotation covers the use of quaternions for rotation in some detail.  I'm too lazy to digest the entire article, but about 2/3 of the way down you can see "from a quaternion to an orthogonal matrix" .  One thing to keep in mind is that the 4 numbers of a quaternion are NOT fully independent.  I can't remember if blender uses the wxyz where ww + xx + yy + zz = 1 .  Also, quaternions can end up looking really screwy when you're animating rotations and don't tune the curves properly.

I thought I should say something about the statement that was made in the OP's question which was,"to use quaternions, which looks like a 4x4 matrix" .  It may help clear things up a bit to say that quaternions start off looking very different from a matrix.  In graphics, quaternions are translated into matrix format to become compatible with the graphics pipeline, however they start off looking very different(unless you are a trigonomic prodigy.  Then they may look pretty much exactly the same... I don't know, I can't speak for those people :)

The best resource I've found for quaternions is: Quaternions and Rotation Sequences: A Primer with Applications to Orbits, Aerospace and Virtual Reality
by J. B. Kuipers
Link: http://amzn.com/0691102988

The transformations are applied in this order: scale, rotation then translation.
Note that you would need to multiply the matrices in the reverse order to get a single transformation matrix.
For a rotation around one axis you would only need a $2\times 2$ matrix, e.g. a rotation around the z-axis wouldn't change the z-values of the vertices. For $(x,y,z)$ vertices a $3\times 3$ matrix is more convenient since it can hold all rotations. The conversion from $3\times 3$ (orange) to $4\times 4$ is done by adding (green) a $1$ to the bottom right cell and fill the remaining with $0$.
$$
\begin{aligned}
&\begin{bmatrix}
\color{orange}1 & \color{orange}0 & \color{orange}0 & \color{green}0\\
\color{orange}0 & \color{orange}{\cos{\theta}} & \color{orange}{-\sin{\theta}} & \color{green}0 \\
\color{orange}0 & \color{orange}{\sin{\theta}} & \color{orange}{\cos{\theta}} & \color{green}0 \\
\color{green}0 & \color{green}0 & \color{green}0 & \color{green}1\\
\end{bmatrix}\\
R_x = &\begin{bmatrix}
1 & 0 & 0 & 0 \\
0 & \cos{\theta} & -\sin{\theta} & 0\\
0 & \sin{\theta} & \cos{\theta} & 0\\
0 & 0 & 0 & 1
\end{bmatrix}\\
R_y = &\begin{bmatrix}
\cos{\theta} & 0 & \sin{\theta} & 0\\
0 & 1 & 0 & 0 \\
-\sin{\theta} & 0 & \cos{\theta} & 0\\
0 & 0 & 0 & 1
\end{bmatrix}\\
R_z = &\begin{bmatrix}
\cos{\theta} & 0 & -\sin{\theta} & 0\\
\sin{\theta} & 1 & \cos{\theta} & 0\\
0 & 0 & 1 & 0\\
0 & 0 & 0 & 1
\end{bmatrix}
\end{aligned}
$$
A translation vector doesn't fit into this matrix, therefore it is expanded to a 4x4 matrix. This is in order to make translation compatible to the other transformations (This is called Homogeneous coordinates.)
$$
\begin{aligned}
T(d_x, d_y, d_y) &= \begin{bmatrix}
1 & 0 & 0 & d_x\\
0 & 1 & 0 & d_y\\
0 & 0 & 1 & d_z\\
0 & 0 & 0 & 1\\
\end{bmatrix}\\
S(s_x, s_y, s_y) &= \begin{bmatrix}
s_x & 0 & 0 & 0\\
0 & s_y & 0 & 0\\
0 & 0 & s_z & 0\\
0 & 0 & 0 & 1\\
\end{bmatrix}
\end{aligned}
$$
Quaternions are a more complex way to describe rotations which avoids a Gimbal Lock, a situation where you would loose one degree of freedom.
Related questions:

What is the order of transformations when exporting to Collada?
Could someone please explain gimbal lock?
Apply rotation to camera?

Quaternions have always been a mystery to me.  I still use them, and know how to leverage them, but they are just a black box of wonder to me.  No site that I have been to has been able to explain in a reasonable concise manner how they actually work.  Do you know any sites that could explain them?

@zero298 There are different interpretations of quaternions, See the resources http://mathworld.wolfram.com/Quaternion.html , Ken Shoemake's original paper: http://run.usc.edu/cs520-s12/assign2/p245-shoemake.pdf

@zero298 http://www.euclideanspace.com/ is also a very good place that explains a lot of different topics about transformations in space. It has also a lot of useful examples.

Thankyou Stacker for laying out the 4x4 matrix method of extending 3D linear transforms to accommodate translations. The question of how this method combines with quaternion math in Blender still remains to be answered, however. +1 for Ken Shoemake's article! 1985!!!


text:
How to set active scene via Python?
I have code to make a copy of my scene.
bpy.ops.scene.new(type='FULL_COPY')
cloneScene = bpy.context.scene
cloneScene.name = 'clone'

I wish to adapt it so that if the .blend contain several scenes, it will make a copy of the scene named 'Scene', i.e. The default scene (in my use case, it is reasonable to suppose this exists).
First thought is to do:
bpy.context.scene = bpy.data.scenes[ 'Scene' ]

Doc on bpy.context here http://www.blender.org/documentation/blender_python_api_2_57_release/bpy.context.html says 'Note that all context values are readonly, but may be modified through the data api or by running operators'
So I assume I cannot do this.
I found a related thread: http://blenderartists.org/forum/archive/index.php/t-201501.html
which recommends:
bpy.data.screens['Default'].scene = bpy.data.scenes['Scene']
bpy.context.screen.scene=bpy.data.scenes['Scene']

But I don't understand what's going on here, so I'm hesitant to blindly copy the code across.  Does each sub-window have an associated screen, so my 3-D view could be viewing one scene whereas the animation view could be looking at another?

The older answers here are invalid as of 2.80. The Python API has changed, and screen objects no longer have scene as a property. In addition, the window object owns the active view layer.
Now, you can:
bpy.context.window.scene = someScene
bpy.context.window.view_layer = someVL
API doc for window object: https://docs.blender.org/api/current/bpy.types.Window.html#bpy.types.Window

Can we have a link to the API docs please?

I've edited my answer to include this :)

From talking with lukas_t on IRC, here is what I have gleaned:
EDIT: I've combined sambler's answer into this also, thanks sambler!
Blender has a number of 'Window' objects. At least one, anyway (where all the action happens -- the main Blender window).
bpy.context.window.

If you open up a modal dialog, like saving a file, that's probably another.
(Question: how to enumerate these?  Just for an exercise in understanding...)
Each window object has an associated 'Screen' component that determines what scene to show, and which areas to display and how to lay them out. (3D View, Outliner View, etc are technically termed areas). You may notice that when you save and reload a .blend, Blender remembers the layout of all these areas.
So the main (default) window's screen can be accessed via any of:
bpy.context.window.screen
bpy.data.screens['Default']
bpy.context.screen

This last one is preferable, seeing as it is hard to imagine needing to use any other screen (can anyone give an example where you might need a different screen?)
Now you need to tell the main screen what scene it should be displaying.
mainScreen = bpy.context.screen
mainScreen.scene = bpy.data.scenes['Scene']

(Note that you can also do it via the pulldown on the infobar!)
Please upvote lukas_t + sambler's answers if this is useful to you, as I'm just compacting information from them.

Just to throw a spanner in the works. (I'm not 100% certain of the best answer)
Yes each screen defines a layout within the window and links to the scene that it uses.
But above that is a window, blender can open multiple windows (that is top level system provided windows). Each window has a screen which must be unique between windows. You can't have two blender windows using the same screen.
So I'm thinking the way to activate a scene would be
bpy.context.window.screen.scene = bpy.data.scenes['Scene']

So when a script is run, bpy.context.window would be the active window as defined by the system - the one that receives clicks and keystrokes.
Thing is it would seem we can't actually alter the screen in a non-active window so this may be irrelevant.


text:
Center and orient mesh of a head
I have a very accurate mesh of my head, captured by photogrammetry (http://ir-ltd.net/)

I would like to rotate and translate it so that it is as symmetrical as possible on the x axis.
How could I go about doing this?
Here is a close up of an ear:

Now maybe I could position a sphere...

And then position one of the opposite side in the same place, and then take the average of their centres, translate that back to the origin, and then perform appropriate rotation.
I can write a Python script that gets as far as the translation, but I'm not sure how to do the final rotation.
Also can anyone think of any other techniques?
PS it is essential to mesh scale must be preserved!
EDIT:
Another technique might involve selecting one ear and calculating the average of all vertex positions. Then doing the same for the other ear.  And then taking the line between these two centroids to be the new X axis.
But then the problem becomes how to select the ear?  Specifically, how to make sure the second ear is selected in a similar way.

So your scanned head is rotated somehow in 3D space, and you want to rotate it to be axis-aligned (with X or Y axis), and the center should be at the scene origin at 0,0,0? (center as in the middle of a virtual line connecting both ears for instance)

Yes!  I can get it pretty close by eye, but not exact.

A easy way would be:

Select three vertices (right, left and middle) on the head;
Create a empty based on that virtual plane using Precise Align.
Select the empty, the AltR. You may want to rotate manually along Z axis if it's not expected after that.
Select your object, AltP > Clear and Keep Transformation. Then delete the empty.

Similar usage like this.
One thing that is worthy mentioning is: it's a scanned head in your case. Since real human body can be just roughly symmetrical, but not exactly as it appears, so the result may not be perfectlly symmetrical as expected. Of course, you can still give it a try.


text:
Python: process mesh so that longest edge length < x
I need to process a mesh so that all of the edges are below a certain threshold, say x units.
(I am throwing a mesh into an acoustic simulator, which requires the longest edge length to be < 1/3 of the maximum wavelength)
How can accomplish this with a Python script?

Example subdividing the default cube.
import bpy
import bmesh

threshold = 0.1
obj = bpy.data.objects['Cube']
bm = bmesh.from_edit_mesh(obj.data)

#do ... while
while True:
    edges = [e for e in bm.edges if e.calc_length() > threshold]
    if not edges:
        break
    bmesh.ops.subdivide_edges(
        bm,
        edges=edges,
        cuts=1
        #use_single_edge=True,
        #use_grid_fill=True
        )
    #triangulate
    bmesh.ops.triangulate(bm, faces=bm.faces, use_beauty=True)

bmesh.update_edit_mesh(obj.data)

And CTRL+T will re-triangulate -- nice!

You can do that with bmesh.ops.triangulate(bm, faces=bm.faces, use_beauty=True)

Here is a full implication of pink vertex's solution:
(Thanks to CoDEmanX!)

# Edge-Splitter
#
# π 11.2.2014
#
# Repeatedly splits all edges with length > max_threshold and re-triangulates
#
#   To load, one of the following:
#      1) paste into blender's inbuilt text editor, which has a menu option for "run script", which you need to do.
#      2) type into blender python prompt:
#        f='/path/to/???.py'; exec(   compile( open(f).read(), f, 'exec' )   )
#      3) Place in Blender's Addons folder (on my Mac it is /Applications/Blender.app/Contents/MacOS/2.69/scripts/addons/)
#          and InfoBar -> File -> User Prefs -> Addons -> (find and check it)
#
# NOTE: You can also make your own scripts folder and InfoBar -> File -> User Prefs -> File -> Scripts -> [ type it here ]
#
# To use:
#    * With target object selected
#    * in edit mode
#    * with the mouse over the 3-D view
#   Hit SpaceBar
#
#   ...and search for "LimitEdgeLen"
#
#   Adjust the max edge length in the panel

bl_info = {
    "name"        : "Limit Edge Length",
    "author"      : "pi",
    "version"     : (1, 0),
    "blender"     : (2, 67, 0),
    "location"    : "View3D > T-panel > Object Tools",
    "description" : "foo",
    "warning"     : "",
    "wiki_url"    : "",
    "tracker_url" : "",
    "category"    : "Add Mesh"
    }

import bpy, bmesh

from mathutils import Vector

# http://blenderscripting.blogspot.co.uk/2013/05/adding-geometry-to-existing-geometry.html

def main( context, maxlen ):
    obj = bpy.context.object
    me = obj.data

    bpy.ops.object.mode_set( mode = 'EDIT' )

    bm = bmesh.from_edit_mesh( me )

    #do ... while
    while( True ):

        long_edges = [ e for e in bm.edges if e.calc_length() > maxlen ]

        if not long_edges:
            break

        bmesh.ops.subdivide_edges(
            bm,
            edges=long_edges,
            cuts=1
            #use_single_edge=True,
            #use_grid_fill=True
           )

        bmesh.ops.triangulate( bm, faces=bm.faces, use_beauty=True )

    # update, while in edit mode
    # thanks to ideasman42 for making this clear
    # http://blender.stackexchange.com/questions/414/
    bmesh.update_edit_mesh( me )

    # bpy.context.scene.update()

class MESH_OT_limit_edge_length( bpy.types.Operator ):
    """Tooltip"""
    bl_idname = "mesh.limit_edge_length"
    bl_label = "Limit Edge Length"
    bl_options = {'REGISTER', 'UNDO'}

    maxlen = bpy.props.FloatProperty(
        name        = "Max Length",
        description = "Subdivide edges until below this value",
        default     = 0.5,
        min         = 0.001,
        max         = 999
        )

    @classmethod
    def poll( cls, context ):
        return ( context.object is not None  and
                context.object.type == 'MESH' )

    def invoke( self, context, event ):
        return context.window_manager.invoke_props_dialog( self )

    def execute( self, context ):
        main( context, self.maxlen )
        return {'FINISHED'}

def draw_func( self, context ):
    layout = self.layout
    layout.operator( MESH_OT_limit_edge_length.bl_idname )

def register( ):
    bpy.utils.register_class( MESH_OT_limit_edge_length )
    bpy.types.VIEW3D_PT_tools_objectmode.prepend( draw_func )

def unregister( ):
    bpy.utils.unregister_class( MESH_OT_limit_edge_length )
    bpy.types.VIEW3D_PT_tools_objectmode.remove( draw_func )

if __name__ == "__main__":
    register( )


text:
Programmatically generate random point-cloud within solid mesh
I think I'm nearly there, thanks to two super scripts from CoDEmanX.
The first script shows the bounding box around an object:
import bpy
import bgl
from mathutils import Vector

def draw_callback_px(self, context):

    ob = context.object
    if ob is None or ob.type not in ('MESH', 'CURVE', 'SURFACE', 'META', 'FONT'):
        # Type that doesn't support .bound_box
        return
    mat = ob.matrix_world

    # 50% alpha, 2 pixel width line
    bgl.glEnable(bgl.GL_BLEND)
    bgl.glColor4f(1.0, 0.0, 0.0, 0.5)
    bgl.glLineWidth(2)

    bbox = [mat * Vector(b) for b in ob.bound_box]

    bgl.glBegin(bgl.GL_LINE_STRIP)
    bgl.glVertex3f(*bbox[0])
    bgl.glVertex3f(*bbox[1])
    bgl.glVertex3f(*bbox[2])
    bgl.glVertex3f(*bbox[3])
    bgl.glVertex3f(*bbox[0])
    bgl.glVertex3f(*bbox[4])
    bgl.glVertex3f(*bbox[5])
    bgl.glVertex3f(*bbox[6])
    bgl.glVertex3f(*bbox[7])
    bgl.glVertex3f(*bbox[4])
    bgl.glEnd()

    bgl.glBegin(bgl.GL_LINES)
    bgl.glVertex3f(*bbox[1])
    bgl.glVertex3f(*bbox[5])
    bgl.glVertex3f(*bbox[2])
    bgl.glVertex3f(*bbox[6])
    bgl.glVertex3f(*bbox[3])
    bgl.glVertex3f(*bbox[7])
    bgl.glEnd()

    min_x = min(b.x for b in bbox)
    max_x = max(b.x for b in bbox)
    min_y = min(b.y for b in bbox)
    max_y = max(b.y for b in bbox)
    min_z = min(b.z for b in bbox)
    max_z = max(b.z for b in bbox)

    bgl.glColor4f(0.0, 1.0, 0.0, 0.5)
    bgl.glBegin(bgl.GL_LINE_STRIP)
    bgl.glVertex3f(min_x, min_y, min_z)
    bgl.glVertex3f(min_x, max_y, min_z)
    bgl.glVertex3f(max_x, max_y, min_z)
    bgl.glVertex3f(max_x, min_y, min_z)
    bgl.glVertex3f(min_x, min_y, min_z)
    bgl.glVertex3f(min_x, min_y, max_z)
    bgl.glVertex3f(min_x, max_y, max_z)
    bgl.glVertex3f(max_x, max_y, max_z)
    bgl.glVertex3f(max_x, min_y, max_z)
    bgl.glVertex3f(min_x, min_y, max_z)
    bgl.glEnd()

    bgl.glBegin(bgl.GL_LINES)
    bgl.glVertex3f(max_x, min_y, min_z)
    bgl.glVertex3f(max_x, min_y, max_z)
    bgl.glVertex3f(min_x, max_y, min_z)
    bgl.glVertex3f(min_x, max_y, max_z)
    bgl.glVertex3f(max_x, max_y, min_z)
    bgl.glVertex3f(max_x, max_y, max_z)
    bgl.glEnd()

    # restore opengl defaults
    bgl.glLineWidth(1)
    bgl.glDisable(bgl.GL_BLEND)
    bgl.glColor4f(0.0, 0.0, 0.0, 1.0)

class ModalDrawOperator(bpy.types.Operator):
    """Draw a line with the mouse"""
    bl_idname = "view3d.modal_operator"
    bl_label = "Simple Modal View3D Operator"

    def modal(self, context, event):
        context.area.tag_redraw()

        if event.type in {'ESC'}:
            bpy.types.SpaceView3D.draw_handler_remove(self._handle, 'WINDOW')
            return {'CANCELLED'}

        return {'PASS_THROUGH'}

    def invoke(self, context, event):
        if context.area.type == 'VIEW_3D':
            # the arguments we pass the the callback
            args = (self, context)
            # Add the region OpenGL drawing callback
            # draw in view space with 'POST_VIEW' and 'PRE_VIEW'
            self._handle = bpy.types.SpaceView3D.draw_handler_add(draw_callback_px, args, 'WINDOW', 'POST_VIEW')

            context.window_manager.modal_handler_add(self)
            return {'RUNNING_MODAL'}
        else:
            self.report({'WARNING'}, "View3D not found, cannot run operator")
            return {'CANCELLED'}

def register():
    bpy.utils.register_class(ModalDrawOperator)

def unregister():
    bpy.utils.unregister_class(ModalDrawOperator)

if __name__ == "__main__":
    register()

    for area in bpy.context.screen.areas:
        if area.type == 'VIEW_3D':
            context = bpy.context.copy()
            context['area'] = area
            bpy.ops.view3d.modal_operator(context, 'INVOKE_DEFAULT')
            break

The second script generates a point cloud within that bounding box:
import bpy
from mathutils import Vector
from random import uniform

def main(context, num):

    ob = context.object
    mat = ob.matrix_world.copy()
    mat.col[3][:3] = [0] * 3 # reset translation

    bbox = [Vector(b) for b in ob.bound_box]
    xmin, xmax = bbox[0].x, bbox[6].x
    ymin, ymax = bbox[0].y, bbox[6].y
    zmin, zmax = bbox[0].z, bbox[6].z

    me = bpy.data.meshes.new("Random points")
    me.vertices.add(num)

    for v in me.vertices:
        v.co = mat * Vector((uniform(xmin, xmax), uniform(ymin, ymax), uniform(zmin, zmax)))

    ob_new = bpy.data.objects.new("Random points", me)
    ob_new.location = ob.matrix_world.translation
    ob_new.show_x_ray = True
    bpy.context.scene.objects.link(ob_new)
    bpy.context.scene.update()

class SimpleOperator(bpy.types.Operator):
    """Tooltip"""
    bl_idname = "object.simple_operator"
    bl_label = "Simple Object Operator"
    bl_options = {'REGISTER', 'UNDO'}

    amount = bpy.props.IntProperty(name="Amount",
        description="Number of random points to generate",
        default=100,
        min=1, max=10000
        )

    @classmethod
    def poll(cls, context):
        return context.object is not None

    def execute(self, context):
        main(context, self.amount)
        return {'FINISHED'}

def register():
    bpy.utils.register_class(SimpleOperator)

def unregister():
    bpy.utils.unregister_class(SimpleOperator)

if __name__ == "__main__":
    register()

(NOTE: of course the first script is completely unnecessary, but it looks pretty!)
Result:

What I'm trying to do is insert a check to see whether the generated point is within the object.
The way I'm doing this is to generate a pair of points within the bounding box, A and B.  now I raycast along that line.
Imagine you had a ray starting inside the object. When it hits the surface, the normal vector of the surface at that point will be aligned with the ray.  Specifically the angle between the ray and the normal vector will be < 90°.
I've got it to run without producing errors, but now it isn't producing points either.

NOTE: Instructions: paste script in the blender text editor, text -> run script
Do this for both scripts
Now with the mouse over the 3-D view, hit the spacebar -> 'simple object operator'

Woot!
EDIT: new version: just put it in your /scripts/addons/ and load it in through blender's user preferences -> add-ons

PointCloud Generator
#
# CoDEmanX, pi
# 19.1.2014
#
# Generate random points within the volume of a mesh
#
# Point testing is done by projecting the point in the positive X direction;
#    if the first collision is with the inside of the mesh, the point is considered to be inside
#
# To load:
#   To load, Either:
#        paste into blender's inbuilt text editor, which has a menu option for "run script", which you need to do.
#   Or type into blender python prompt:
#        f='/Users/pi/Dev/blenderAddons/pointcloud.py'; exec(   compile( open(f).read(), f, 'exec' )   )
#
# To use:
#    * With target object selected
#    * in edit mode
#    * with the mouse over the 3-D view
#   Hit SpaceBar
#
#   ...and search for "PointCloud"
#
#   Adjust the number of points in the panel

bl_info = {
    "name": "PointCloud Generator",
    "author": "CoDEmanX, pi",
    "version": (1, 0),
    "blender": (2, 67, 0),
    "location": "View3D > T-panel > Object Tools",
    "description": "Generate random points within the volume of a mesh",
    "warning": "",
    "wiki_url": "",
    "tracker_url": "",
    "category": "Add Mesh"}

import bpy
from mathutils import Vector
from random import uniform

from math import pi

def pt_in_box(O,P):
    return Vector( (
                uniform( O.x, P.x ),
                uniform( O.y, P.y ),
                uniform( O.z, P.z )
            ) )

def main(context, num):
    max_attempts = 999

    context.scene.update()

    ob = context.object

    mat = ob.matrix_world.copy()
    mat.col[3][:3] = [0] * 3 # reset translation

    bbox = [Vector(b) for b in ob.bound_box]

    O = bbox[0]
    W = bbox[6]

    X = Vector( ( W.x - O.x, 0.0, 0.0 ) )
    #Y = Vector( ( 0.0, W.y - O.y, 0.0 ) )
    #Z = Vector( ( 0.0, 0.0, W.z - O.z ) )

    me = bpy.data.meshes.new("pointcloud")
    me.vertices.add(num)

    for v in me.vertices:
        got = False

        for i in range(1,max_attempts):
            A = pt_in_box( O, W )

            (location, normal, index) = ob.ray_cast(A, A+X)

            # don't need X.angle(hit.normal), woot!
            if index > -1  and  normal.x > 0.0 :
                got = True
                break

        if not got:
            print( "PtCloud Failed" )
            return

        v.co = A

    me.transform(mat)

    ob_new = bpy.data.objects.new("pointcloud", me)
    ob_new.location = ob.matrix_world.translation
    ob_new.show_x_ray = True
    bpy.context.scene.objects.link(ob_new)
    bpy.context.scene.update()

class PointCloudGenerator(bpy.types.Operator):
    """Tooltip"""
    bl_idname = "object.pointcloud"
    bl_label = "PointCloud"
    bl_options = {'REGISTER', 'UNDO'}

    amount = bpy.props.IntProperty(name="Points",
        description="Number of random points to generate",
        default=100,
        min=1, max=25000
        )

    @classmethod
    def poll(cls, context):
        return context.object is not None

    def execute(self, context):
        main(context, self.amount)
        return {'FINISHED'}

def draw_func(self, context):
    layout = self.layout
    layout.operator(PointCloudGenerator.bl_idname)

def register():
    bpy.utils.register_class(PointCloudGenerator)
    bpy.types.VIEW3D_PT_tools_objectmode.prepend(draw_func)

def unregister():
    bpy.utils.unregister_class(PointCloudGenerator)
    bpy.types.VIEW3D_PT_tools_objectmode.remove(draw_func)

if __name__ == "__main__":
    register()


text:
How to install numpy for blender-python (OSX)
I've been googling for this, and I can't find a definitive answer.
Here are of the options I can find:

https://plus.google.com/106742462387083223310/posts/696yEuzhf2b
which suggests: 'sudo python3.2 setup.py install --install-lib /usr/lib/blender/scripts/modules/'
but I don't see how that has anything to do with numpy, so I'm going to skip this one for now.
http://blenderartists.org/forum/showthread.php?324822-Another-NumPy-issue
Install numpy using existing Python3, and then manually copy /numpy folder over
I've tried this, as below, and it fails just the same as in that thread
Delete Blender's Python, forcing it to fall back upon  the system Python installation
I'm reluctant to do this as I want this module to be publicly usable, and I don't like the idea of requiring people to cobble their blender to make it work.

So, going with (2):
I'm on OS X and I have a separate Python3 courtesy of Homebrew.
piBookAir:~ pi$ pip install numpy

piBookAir:~ pi$ python3
Python 3.3.4 (default, Mar  8 2014, 14:52:56)
[GCC 4.2.1 Compatible Apple LLVM 5.0 (clang-500.2.79)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import numpy
>>> print( numpy.__file__ )
/usr/local/lib/python3.3/site-packages/numpy/__init__.py

So now I copy the /numpy folder over to ~/BlenderScripts/modules/
(I have set ~/BlenderScripts as my scripts folder)
I restart Blender, go into the Python console:

The error is "ImportError: cannot import name add_newdocs"
What am I doing wrong?
Also, if I may bundle two questions into one, can I copy my ~/BlenderScripts onto a fresh system (maybe with a different operating system) and expect a script that imports numpy to still work?

Numpy is included in Blender 2.70 on Windows, Mac OS X and Linux.

Super! I was on 2.69

It won't use other python distribution, but using the following code you can install other packages using pip:
https://github.com/pelednoam/mmvt/blob/master/src/misc/install_blender_reqs.py


text:
Choose 10,000 random points inside mesh
I'm going to be throwing a mesh into a BEM acoustic simulator.
There is a well-known resonance problem with BEM acoustic simulators --if you test for a frequency that matches one of the resonance modes of the mesh, it goes crazy.
There is a known workaround which involves creating random points inside the mesh, so that's what I would like to do.
How would I go about implementing a python script to do this?
I'm assuming scripting is the best way, please someone correct me if I'm wrong here.
EDIT: how about picking a random point-pair P Q, intercepting it with the mesh, and if there are exactly 2 points of intersection A and B, then use A + t(B-A) where t is randomly chosen between 0 and 1
For a closed mesh of a human head and shoulders (so mostly convex), a significant number of points pairs should produce a valid result
The only question is: can I determine the points at which a line hits a mesh?
EDIT: mathutils.geometry.intersect_ray_tri from http://www.blender.org/documentation/blender_python_api_2_65_5/mathutils.geometry.html
EDIT: http://www.blender.org/documentation/248PythonDoc/Mesh.Mesh-class.html#pointInside

There is  way to do this without python, using particles.

Create a particle system and pick volume and random as the distribution settings:

Also set the physics to none to conserve processing power.
You'll want to set the Number to 10000, but I don't think the computer I'm currently on will like that :P.
Create a one-vertex object. The easiest way to do this is by adding a plane and deleting three vertices. After you delete the extra verts, switch back to object mode (Tab) and press ShiftCtrlAltC> Origin to geometry to snap the origin to the single vertex.
Pick your single vertex object as the particle system object in Particles > Render:

With the object with the particle system selected, press Convert on the particle modifier in the  modifiers tab:

Join the resulting vertices to your object with CtrlJ (everything should already be selected correctly). Remember to remove the particle system, as pressing Convert does not delete it.

Result:

I am having a huge problem. I really need to use this technique for a project of mine, but when I press "convert", nothing happens. Sometimes, if I change either of the booleans that appear in the toolbox upon pressing "convert" - that is, the "parent" and "keep hierarchy" buttons - all the duplicated objects disappear and I find one little duplication in the corner of the emitter mesh. It is very strange. Do you have any idea how to counter this and make all the particles convert to individual objects like they're supposed to? Do you think this could possibly be a bug?

Actually, never mind! The way I figured it out, well, let's just say it was a bug. There was a question that was referencing this answer to solve answer the question, and it mentioned that a keyboard shortcut for the convert button was Ctrl + Shift + A. I used that and... everything seems to be smooth sailing. Here's that said question. It's got to be a bug.

There's a utility function to generate random points on faces:
import bpy_extras.mesh_utils
bpy_extras.mesh_utils.face_random_points(num_points, tessfaces)

Generates a list of random points over mesh tessfaces.
:arg num_points: the number of random points to generate on each face.
:type int:
:arg tessfaces: list of the faces to generate points on.
:type tessfaces: :class:`bpy.types.MeshTessFace`, sequence
:return: list of random points over all faces.
:rtype: list

Random points inside your mesh is more troublesome, since meshes aren't volume-based (there's not necessarily an inside). You could have a look at the 3D Print Toolbox addon, which is able to determine the volume of a mesh and uses normals and angles for that. You oculd probably use something similar to determine whether a point is inside the mesh or not (as long as the mesh is "solid").

wow, that's a gem I've been missing for a while!


text:
ReMeshing two vertex groups to different resolutions
Some modifiers allow me to select a vertex group upon which to operate.
The remesh modifier doesn't.
I've got a 3-D mesh of a head, and I need the ears remeshed to a very high resolution and the rest of the head to a much lower resolution.
I have created 2 vertex groups.  Now I could {save, remesh, export to .OBJ} for each group, then create a blank project and import both .OBJs.
Assuming the re-meshing process has not messed up the join-perimeter, they should still fit together.
Is this the best way to do this?
EDIT: I've just realised that the perimeter will be messed up.   Say you have a cylinder with 100 points around the circle.   Cut it in half, now you have two cylinders.  Reduce one of them so it has 10 points around the circle. Now obviously these are not going to match up.  So is there some way to 'glue' them back together?

I don't think there will be any way to get a clean join between the ears and the head, as each will have very different vertex counts around the edges.

Yes.. It's called the remesh modifier :P This will make a manifold mesh that includes both of them, with even mesh density. I think you will have to have some triangles if you want to have dramatically different mesh densities on a single mesh.

you could always seperate the mesh (select the ear in edit mode, hit P and seperate based on selection) then remesh each object individually, apply the modifier, and then join (and manually stitch or use bridge if possible)

I agree with this. And additional bridge work is needed after that. If you are still critical about the bridge area, then just use Dynapic Sculpt to remesh that part.

In order to avoid breaking it into parts, I'd recommend remeshing the whole model into a LOWER resolution (including the ears) and then use the sculpting tools to paint more geometry onto the ears by themselves.


text:
How to project 3D point into camera under the influence of focal length and use Python?
The manual introduces the world_to_camera_View maps 3D to 2D, but ignores the influence of focal length parameters. Is there a method with focal length parameters in blender API? Is it possible to implement it in Python? thank you!
thank you!
Best regards!

import bpy

from mathutils import Vector
from bpy_extras.object_utils import world_to_camera_view

scene = bpy.context.scene

cam = bpy.data.objects["Camera"]
vec = Vector()
vec.x, vec.y, vec.z = 0, 0, 0

cam.data.lens = 50 # 50mm
xy = world_to_camera_view(scene, cam, vec)
print(xy)

cam.data.lens = 100
xy = world_to_camera_view(scene, cam, vec)
print(xy)


text:
Fluid baking stops without errors
I have setup a simple scene with some hills (one big object) and dam with water. Dam consists of multiple objects, they are set up as fluid obstacles. Dam breaks (parts of dam are animated with keyframes) and water should start to flow through valley.
But, fluid baking stops on higher fluid resolutions (for example 300) somewhere in the middle of my animation when dam breaks.
What I have already tried:

applied scale and rotation on fluid objects
removed double vertices and recalculated normals on fluid objects
run blender from command line and also with -d switch (to see debug output), but haven't seen any errors, it just suddenly stops
manually cleared the fluid cache folder (deleted all the files)
set all fluid obstacles to Free Slip (as advised in Blender Cookie Fluid Simulation Tutorial, part 3)

I am using blender 2.69 64bit on Ubuntu 13.10.
Here you can download my scene (it is my first try with Blender, so it is very simple) - scena1_2.blend (30 MB - sorry for that size, some textures are included...)

From the sounds of it, it bakes fine at lower resolution? It's hard to say where the problem is without a Blend file.

Your file bakes fine for me at 300 resolution using Blender 2.7 (it did fail with 2.69 though).

There exists a workaround (at least it works 100% in my setup)!
I have enabled Export Animated Mesh option for all moving fluid obstacle objects and it works!
The only downside is that it enforces No Slip and is slower according to the documentation inside Blender.

There are two things that might be going on.

Your cache is baking a different range of frames than are on your timeline. Make sure that the frame range in the cache settings is what you want it to be, because it might not be the same as your timeline range.
Your baked physics aren't getting freed, properly, and it's continuing to re-use old simulation data without re-calculating it.

This, in turn, might be for a number of different reasons:
You might not know that you have to "free bake" (in the cache settings) in order to run the bake again.
You might be using "disk cache" or "external." External uses a particular set of physics cache files and won't change them, even if you free the bake. This is unlikely, tho, because IIRC, the baking buttons go away when you turn this on.
Blender is acting up. There is a known issue with Blender releasing caches properly with any of the simulators, including smoke and particles. There are a few work-arounds. The work-around that I consider easiest is to change some "significant" value after freeing the bake. This will usually fully free the baked files and allow you to re-compute the simulation. There are some values that will do this and some that won't. You can tell when the files are freed because the colored line at the bottom of the timeline will change. Sometimes you ALSO have to track all the way back to the beginning of the animation. The most fail-safe method is to find the folder named blendcache_[filename] and delete its contents.

Hope that helps!

ad 1) it is not the problem, because when I set resolution for ex. to 80, it bakes whole animation

...but when you go back to another resulution, it doesn't bake completely?

when I go to higher resolutions, like 300, it will stop baking somewhere in the middle

Huh... that's weird. That might actually be a bug. Have you checked the bug reports for something like this?

I haven't checked bugs especially, but I googled about that a lot and haven't found any big known bug...

And, I have also another similar scene and I haven't had any problems while baking with higher resolutions..

I'd recommend looking at the output in the info window and console to see if maybe it's running into trouble creating the files, or something else. You might also run Blender from the command line, to see if it's printing out extra information that you're not seeing otherwise.

Yes, I have already tried it, I have also tried running from command line with -d switch (debug output) but there is nothing strange, it just suddenly stops... And now, I have also tried clearing the cache folder manually but it didn't help...

@betatester07 I have had this too.. Is it possible you are running out of memory?

Those physics caches can be outrageously huge, sometimes.

@gandalf3 I don't think so. I have 64 bit Ubuntu, 64 bit Blender, 6GB of RAM. During baking, my System Monitor shows 2.2GB RAM usage...

@betatester07 I think it's a bug, you might want to try reporting it. For what it's worth, the same thing happens in this Blender Cookie tutorial. He managed to get it to work by "making the simulation easier".

thanks, but it is still not working. I tried setting all moving obstacles to Free Slip, but still tha same problem. I also tried to reduce the number of my moving obtacle pieces to 60, but no luck..

@betatester07 Have you reported this as a bug yet? If you aren't planning on it, do you mind if I use your blendfile to report it?

no, I wanted to do some more testing first and i didn't have much time last days. but maybe it will be better to report it as soon as possible. so, feel free to use my blendfile to report it and let me know.


text:
Wierd mesh deformation ( maybe a Duplicate? )
I know there is a problem like this somewhere but i dont know what it is called / what to research so i thought i should ask it here . It is obviously a duplication of a question and i will take it down once i get a link / answer
My question is , why is my mesh getting deformed when i apply weights? Normals are correct , i have removed doubles and it works perfect for the upper half of the body.


text:
Set multiple origins to geometry?
I have lets say 5 individual vertexes objects with the origin all set to the centre of the screen. How could I set each vertex to the geometry of each vertex?

Sorry, I ment 5 Indiviaul vertexes that are their own object.

So you mean 5 objects, each object contains its own mesh(with vertices). And there are 5 vertices on separated meshes you chosen. You want them as their parent object origins?

https://blender.stackexchange.com/questions/24078/set-origin-to-geometry-center and https://blender.stackexchange.com/questions/14294/how-to-recenter-an-objects-origin/14296#14296

and perhaps  https://blender.stackexchange.com/questions/134440/shortcut-for-setting-origin-to-vertex

In 2.79, in object mode, with all objects selected, ShiftCtrlAltC will send the origins of all the objects to their geometry simultaneously.
in 2.8, until you set a personal shortcut, it's available only through the header > Object > Set Origin menu.
Or, Enable the shipped add-on '3D Viewport Pie Menus' > 'Origin Pie'.. which has the advantage of working in Edit Mode. That lets you set the origin to a selection of the geometry.

Strange, It wasnt working before now it does..?? Thanks !

..@Knuckles209cp I think I vaguely remember a time when it didn't work, too


text:
Glitching normal map artifacts
I'm getting strange artifacts in my normal map as you can see from the photos. Yes, I've checked all the normals and recalculated them several times. Yes, I have removed all doubles. Yes, All scale/transforms are reset. Yes, no other objects are overlapping. Yes, The object is large enough where it wont effect baking. Yes, I've tried baking both tangent and object space. I'm out of ideas, I am using Blender 2.81.

It looks like there are overlapping faces. This can be within one object.

The object in the photo is the high & low poly on top of each other, I can give the .blend if you would like to try it?

No, thanks. I know almost nothing about baking.

The ray distance has to be non-zero, increase it to avoid the problem.

Maybe give a how-to screenshot.


text:
Weak/No shadows? ( EEVEE )
Ive created a shadow catcher to suit an HDRI image. The shadow catcher is only basically doing ambient occlusion and there is no signs of shadows. There should be an entire shadow under the car.

Can you post the material nodes of the shadow catcher? Or a .blend? Also, shadow catchers in eevee are only a hacky way to do proper shadow catchers, I'd suggest looking more into the topic, there are some good tutorials on youtube.

I've edited the post with the shadow catcher node.

Try this setup:

I only changed the diffuse color and the white handle on the color ramp. I also had a downwards facing sun lamp. Which, mind you, will ruin the shadow catcher if you rotate it beyond a certain point, you can play around with that and try to compensate those two values I changed to your own scene.


text:
Make ends of hair mesh sharp
I made a 3D model of a girl from a game I play and I have the hair all set up, but it's flat on the ends and I don't know how to fix that.

Are you using BI or Cycles?

bi .... thats the render :)

BI
Reduce the value of Tip to in the hair material under Materials > Strand > Size:

Cycles
Again decrease the value of Tip, but in Particle Settings > Cycles Hair Rendering:

Hm , that doesn't seem to be working? do you have any other ideas?

@Knuckles209cp Are you using Paths or Objects as hair particles? Could you add some screenshots of your material and particle settings (or upload your .blend)?

I dont have particle settings , i am using a mesh for my hair . ill take some pictures of the settings for you

@Knuckles209cp Ohh.. you mean that they are all basically mesh planes?

Yes :) , i have the actual girl from the game if you want to look? https://www.google.co.nz/search?q=final+sarah&espv=210&es_sm=91&source=lnms&tbm=isch&sa=X&ei=OsnqUoDiAYSGkQWg_oGIDA&ved=0CAkQ_AUoAQ&biw=1916&bih=898#q=final+fantasy+sarah&tbm=isch&facrc=&imgdii=&imgrc=mbkZpehO7waGVM%253A%3BZP6DbmJc6fhtNM%3Bhttp%253A%252F%252Fwww.creativeuncut.com%252Fgallery-18%252Fart%252Fff13-2-serah-portrait.jpg%3Bhttp%253A%252F%252Fwww.creativeuncut.com%252Fgallery-18%252Fff13-2-serah-portrait.html%3B1000%3B1100

Oh the question was ment to say MESH instead of particle , my fault sorry

@Knuckles209cp Could you use an alpha texture to make it look like they're sharp? Or do they really need to be sharp?

i could do the alpha texture ... is it possible to do it any other way though??

@Knuckles209cp Well, how easy it is depends on the topology of the hair, if the hair pieces are separate objects, have linked mesh data (and are deformed by a modifier), etc.

ALL the hair is just one mesh


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Setting the pivot point of an object
I have a sword that currently rotates around a pivot point thats off of the actual object. Im new to blender and im not sure how i would go about changing it so that the sword rotates around the handle. Any help would be appreciated!

Related: http://blender.stackexchange.com/q/1291/599

You need to either change the origin of the object, or use the 3D Cursor as a pivot point.
A quick way to change what is used as a pivot point, is to look at the bottom menu in the 3d view and select "Pivot center for rotation/scaling":

But to actually change the object's origin, you could first move the 3D Cursor to whereever you want the pivot point. To do this accurately, you can snap it to whatever you have selected (both in Object Mode and Edit Mode by pressing Shift-S and choosing "Cursor to selected".

Then, in Object Mode with you object selected, use the Object Tools menu on the left (T to make the menu appear if you don't see it), press Origin button, and choose "Origin to 3D Cursor".
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For Blender 2.8:
The 'Pivot Point' selector can be found at the top of your viewport in a drop-down with a double 'chain-link' icon on it

Although, if your pivot point is far off the object itself, "cursor to selected" will place the cursor... Outside the object! Placing the pivot point back inside the object is sometimes hard

That helped me, but I actually had to select the object in Object Mode, go in Edit Mode, snap Cursor to Selected, then go back to Object Mode, then Origin to 3D Cursor. Doing in Object Mode only wouldn't allow me to snap (working with Curves here).


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What is the fastest way to create a curved plane?
For a background, a lot of times I need a vertical wall, horizontal bottom, and a nice connecting curved surface between them in front of the camera. So far, I have used two methods:

Deform a plane along the curve. This takes some time to get it right, as curve deformations are tricky, and it is almost impossible to make it truly horizontal or vertical.
Create a cube, add bevel, apply, remove unnecessary parts of the mesh. Bevel tends to have artifacts around the corners of the cube for large bevel values and number of segments (e.g 25% of the cube side length, 64 segments).

What do you use? Am I missing some basic technique?

The fastest way I can think of is:

Add a mesh cube
Delete two vertices (so that you're left with a right angle)
ctrl1 to add a subsurf modifier
and then ctrlr to add an edge loop near the end of each face so that the ends are square (I can't post screenshots at the moment, sry).
done

Andrew Price does something similar near the middle of this tutorial (at time 31:19): http://www.youtube.com/watch?v=5Yd7ad08e54&feature=player_embedded#t=1879
His result is the same, but he starts with a plane instead of a cube.
As a bonus, if you're willing to learn a little Python and Blender coding, it's not hard to make an add-on that would add that object as a primitive in the Add->Mesh menu.

There is already an addon which will add a custom user made mesh as a primitive (I think it's called Creaprim)

I usually do it like this, it's the quickest I've been able to find.

Add a curve (I like to use paths because they are initialised as a straight line)

Change its shape around a bit

Convert it to a mesh Altc

Extrude (in edit mode, e)

Admire the beauty.

Awesome, thanks! For my particular purpose (vertical and horizontal planes connected) I like Matt's approach with subsurf a little better, but would use the above technique for a lot of other stuff. Would give you more votes if I could :)

@AlexPakka You could extrude it multiple times as well. Of course, Matt's is neater :)

Another way is to use a plane and bevel it in edit mode. I can do the following steps in about 10 seconds (including the time to start and stop the timer).

Add plane (⇧ ShiftA > Mesh > Plane):

Switch to edit mode (↹ Tab), select one edge (A > deselect all, B > border select), and extrude it upwards (E):

Select the corner edge again (A to deselect all, B for border select)

Bevel with CtrlB. Use the keyboard or the scrollwheel to set the number of segments:

Shade smooth.

Example (click the gif for a video version which can be slowed down):

Convenience:
If you find your self creating these objects for what seems like every other project, you could either:

Make a primitive out of it with the CreaPrim addon so it's available in the Add mesh menu. (See this answer for instructions)

or:

Include one in your startup.blend on a separate layer (this is what I did):

Open a new file
Create the "bent plane" object and optionally move it to another layer.
Save the startup.blend (CtrlU). Note that this will save everything (view angle, materials, objects, user preferences, etc.) as it is as the way blender will start in the future.
See this question for more information.

This is a good idea, but it is also #2 on the OP's list of known solutions.

@Matt I think the OP was using the modifier, as they said "apply"

I was under the impression that ctrl-B added a Bevel modifier. Does it not?

@Matt No, it bevels the selected edges (I'll put up some images in a second)

The screencast is too fast for the key sequence to be read.

@mins The screencast is intentionally fast, to demonstrate that it can be done quickly. Unfortunately the poor framerate leaves out a lot of information. I've added all the key presses in the text and uploaded a better screencast which can be sped up/slowed down.

The absolute fastest way to do this is to just add a plane, extrude one side and crease all the edges (ShiftE) except the one where the planes join (you can also select the edges and increase the Mean Crease in the properties panel). Next add a subsurf modifier and shade it smooth, much less polys than the other solutions and an equally nice result.

That is really a fast method with acceptable results!

Add a cylinder and remove its circular faces. Next cut out one-fourth of this cylinder and let everything else go. Scale it according to size needed and it gives an L-shaped curved backdrop. Also add subsurf and smooth shading to get that curved look

Add a cylinder with a radius of the desired curve.
Delete 3 quarters of the cylinder, leaving a curve over 90 degrees.
Extrude the lower edge horizontally and the upper edge vertically.


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why does loop-cut-and-slide ignore some faces but not others?
why does the loop-cut-and-slide operation ignore certain faces but happily cut others?the model is symmetrical so it is a bit strange to pick 3 faces that won't get cut. I tried applying it to see if it was just a graphics glitch causing the purple line to not display over everything, but it did end up cutting only what the line was selecting, instead of the whole mesh.

as requested,here's a paste of the blend:
http://www.pasteall.org/blend/27821

Hard to say just by looking but you more than likely have inside or duplicate faces. Share the model so we can have a look at it.

where should I upload it?

@ZCoder PasteAll  is a nice blender specific site

Related: http://blender.stackexchange.com/a/3632/599

First you should fix the mesh. This might be part of the problem.

Remove the double geometry, W -> Remove Doubles
Select all geometry, A
Recalculate the normals, Ctrl N

Does the problem persist? If so you might have to do some manual cleanup. The problem might be that you have ngons in your mesh.

To see if you bad geometry go into vertices mode and Shift Ctrl Alt M to select all non-manifold geometry. If something was selected near at the place where the edge loop does not work that also indicates a problem, if not there still might be a problem
Also to select all n-gons you can do Select -> Select Faces by Sides. Set the number to 4 and the type to Greater Than If you have n-gons they will now be selected.
Go into vertices mode, in face mode it is harder to stop ngons
If you see that there are random vertices along the edges you should delete them, x -> dissolve vertices.

An example of a random vertex along an edge

what does non-manifold mean and how do I fix it? when selecting non-manifold geometry it highlighted edges that are necessary for the model's definition.

@ZCoder See http://blender.stackexchange.com/q/7910/599. It's possible you have duplicate edges/faces or something..

I've been struggling with this issue after extruding a face. Thanks

You have some internal faces (which result in non-manifold geometry):

If you delete them, loop cut works again:

The reason those faces are considered non-manifold is because they have no thickness (they are 2D).
Assuming those faces are desired for a cockpit, try creating a second mesh inside the first (with the normals facing the opposite way) to create a manifold cockpit. The solidify modifier is good for this.

Think of the gaps between the meshes where the normals are facing away as solid, and the faces more as interfaces between solids and air.
Example .blend

so if I copy and paste that mesh I can detach it from the canopy/body mesh and it will still look the same?

@ZCoder I'm not sure what you mean.. Which mesh?

right now the body is all one piece(except the trailfx holders and ball-turrets). the canopy is transparent so something needs to be under it to keep the insides from being visible, hence the cockpit. I was curious if I could just rip/detach that mesh from the main mesh but keep the locations,etc

You could, (loop cut would work), but you would still have a non-manifold mesh (it could not exist in the real world).

I had a face underneath two other faces, made from the vertices of the outer edges of the two faces. removing it did the trick, thank you.


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Blender twisting parts of mesh when rigging
I have a problem when I rig a mesh and that is when I put the arms of my mesh up in the air for example some parts of it get twisted.
I've tried looking at the XYZ orientation and the weight painting with no succes.
Here are pictures illustrating the problem. (possibly NSFW, hover to view)

here is the .blend file
female base rigged

You can upload the file to a service such as pasteall and then share the link here.

ok, thanks I just uploaded the file and edited the post.

This happens only with IK controls on this rigify rig, if you imported this from makehuman you could switch to the mhx rigs where everything works as expected.

I rigged it the normal  way by applying an armature modifier and then making the automatic weights(ctrl + p) i didnt doa  anything in makehuman,  how can i fix that?

The problem in your scene is caused by the bone structure. Take the L side for example:
Since you are using two bones for each upperarm for some reason (which is unlike normal human), the constrained bone DEF-upper_arm.01.L doesn't follow the rotation of its control bone or even DEF-upper_arm.02.L, which would lead to the problem. As shown below:

There would be a few ways to fix this, but I'm really not sure why you structed and set the control bone for upper arm like this (I assume you are trying to simulate the natural-looking muscle stretch). However, I think at least an additional Copy Rotation constraint onDEF-upper_arm.01.L is needed here.
Here is my try, FYI:

oh ok, no I'm starting to get it. I'm just learning 3D graphics as I'm mainly a programmer, so, this is kind of hard for me sometimes.
the way i did it was to add an armature and setting the weights to automatic but as those bones appeared as they are i tought that was the normal setup for the armature. the solution is to make the upperarm just one bone? how can i do it? should i re-rig it?

This is a very complicated rigging. If you are the man who created it, then you may exactly know what you are doing. Yep, you can make it one bone, as well as the lower arm, thighs and shins, since that's how human armature looks like. Or, as I said, you may also add Copy Rotation constraint to the DEF-upper_arm.01.L, to let it follow the rotation of control bone. If it has to.