3d Textures/Volume Textures?

odium

I've searched high and low for any info in making these things, and theres supposed to be a way of making them inside 3ds max for example, but I can't for the life of me even figure out where to start? Does anybody have any experience at all with these things, in any app?

An exmaple of a 3d texture/volume texture:

http://mke3.net/weblog/2008/09/

http://mke3.net/blender/devel/rendering/volumetrics/vol_col_emit.mov
http://mke3.net/blender/devel/rendering/volumetrics/vol_shaded_clouds.mov

odium

Self bump, just the once.

I did have a feeling this would be an alien subject, I haven't seen anybody use them at all yet so just wanted to throw it out there. They are VERY useful or a few things, fog, particles and the like, but as I said, bugger all real solid info because not many people even know about them.

equil

there are two ways in which i've made volume textures.
1. render volumetrics with multiple cameras with different clip planes.
2. "unravel it" and do things in photoshop. a 16x16x16 map might as well be a (16x16)x16 = 256x16 map. this is probably the format you'd export them to a game engine in anyway.

there might be easier ways depending on what you're using them for though.

odium

Yeah, think we discussed the idea of them being VERY low res, simply because they are so memory intensive. But for things like fog volumes, they can make the fog actually look like it has volume, which looks amazing. Thats one simple example, but yeah...

Really struggling to find even the most basic of info online that would talk this through with me, never mind a tutorial. I really am going into this blind

Computron

Wouldn't you be better off writing a 3d function like perlin noise instead? You could even add time and make it more dynamic!

odium

Sadly the whole random noise thing doesn't work too well for most features of this, like smoke and other misc effects.

equil, can you give any more info on what you mean there? Unravel it?

equil

Sorry, missed your question! I mean doing things like this: Colorcorrect3d_base.png. That's a 32x32x32 volume texture where every layer in z is laid out horizontally. In the case above I just have a texture of the RGB color space, and then apply color correction filters to it in photoshop. If you're still interested, I could do a quick writeup on how I rendered volumetric effects using a camera with animated clipping planes.

commander_keen

Rendering 3d textures volumetrically (as in ray tracing through the volume) is pretty expensive which is why its not done in actual games very much. I think Hellgate did it with some explosion smoke or something. More common application of 3d textures in games is sampling their color from geometric surfaces. An example of that is Light Propagation Volumes which lights are projected into and then blured and sampled from actual game geometry to approximate realtime radiosity.