3D Textures [SOLVED]

Scripting Issues
1

Hi all!

I’m trying to create a 3D texture procedurally, that later on I can pass to a fragment shader as a sampler3D. I’m trying to create a GPU equivalent of a CPU octree, by using octree textures as described here: http://http.developer.nvidia.com/GPUGems2/gpugems2_chapter37.html

A teacher of mine explained to me that a sampler3D is nothing more than a buffer whose information is arranged in a certain “format” so that the API can understand it. So for example, I can “transform” my octree into a non-recursive data structure, an array for example, and later on send that “buffer” successfully to the shader (as a sampler3D), if the data is arranged properly.

So my question is the following, how is my data supposed to be arranged in Panda so that I can send it as a sample3D to a fragment shader? Will Panda take care of the “format” regardless of the API being used?

Can my 3D texture be represented in Python by a simple list / tuple?

Thank you very much, and sorry if my question doesn’t make sense (I’m new at using 3d textures)

2

I don’t know much about it but have you read this: panda3d.org/manual/index.php/3-D_Textures ?

3

afaik a 3d texture is nothing else than a textured cube - which may project its textures on another object

in my project i simply create 6 quads, assign them some textures and create a cube with those.
though i 'm not sure if that’s what you’re talking about… sry.

4

Thanks! I’ll take a look to it…

Actually what you are talking about I think it’s called a samplerCUBE which is not the same as sampler3D. If I am not mistaken sampler cubes are used for things such as skyboxes, but what I need is something like this:

http://gpwiki.org/index.php/OpenGL_3D_Textures

(In the section building a simple 3D texture)

Cheers!

5

I’ve been reading more carefully http://www.panda3d.org/manual/index.php/3-D_Textures and http://www.panda3d.org/manual/index.php/Woodgrain_Example

Apparently that’s exactly what I need! I can create the 3D texture in the following way:

tex = Texture('my3dTexture')
tex.setup3dTexture()

for zi in range(texDepth):
    # Create the slices in some way here
    p = blahblahblah

    # Give the slice to the texture
    tex.load(p, zi, 0)

The woodgrain example saves the 3d texture to a file in the disk, so that later on it can be loaded with loader.load3DTexture(). I was wondering if I can omit this saving step, and once I’ve created all the texture slices, send “tex” directly to the fragment shader as a sampler3D.

Will this be possible?

Thanks!

6

Certainly. Once you have created the 3-D Texture, you can do whatever you like with it, including render it with a shader.

David

7

Thanks for the answer David!

I’ll implement this 3-D texture thing in these days and see what can I come up with.

One last thing, for implementing this technique (octree textures, http://http.developer.nvidia.com/GPUGems2/gpugems2_chapter37.html), I need to be able to modify the 3-D texture once it has been uploaded to the GPU, as this paper’s quote states:

So I was wondering if this can be done with Panda. I mean, is it possible to partially update a 3D-texture using the glTexSubImage3D API call?

How does Panda manages this?

Once again, thank you very much!

8

Panda will reload the texture automatically if you change the pixels, but we don’t provide support for a partial update only with glTexSubImage(). For most texture changes, the bandwidth requirements are minimal anyway; though it’s true this may not be true if you have a large 3-D texture. It may be possible to force a call to glTexSubImage() via an OpenGL callback, though this would be complicated. I recommend just using the full-update that Panda provides, until it proves to be a bottleneck.

David

9

Great! Thanks for your advice David!

I’ll try to implement all this stuff in this week, and see how it turns out. I hope it all goes well without using partial updates.

Cheers!