Texture format for wire mesh machines in OpenGL ES 2.0

Question

I need some quick advice.

I would like to simulate cellular automata (from a Simple, efficient method for realistic cloud animations ) on a GPU. However, I am limited to OpenGL ES 2.0 shaders (in WebGL) that do not support bitwise operations.

Since each cell in this cellular automaton is a logical value, saving 1 bit per cell would be ideal. So what is the most efficient way to represent this data in OpenGL texture formats? Are there any tricks or should I just stick with the straight RGBA texture?

EDIT: Here are my thoughts so far ...

At the moment, I am going to go with either the usual GL_RGBA8, GL_RGBA4 or GL_RGB5_A1:

• Perhaps I could select GL_RGBA8 and try to extract the original bits using floating point operations. For instance. x*255.0gives an approximate integer value. However, extracting individual bits is a bit of a pain (i.e. splitting into 2 and rounding a couple of times). I also fear the exact problems.

• If I select GL_RGBA4, I could store 1.0 or 0.0 per component, but then I probably could try the same trick as before with GL_RGBA8. In this case, it is only x*15.0. Not sure if this will be faster or not visible, as there should be fewer operations to extract bits, but less information on reading the texture.

• Using GL_RGB5_A1, I can try and see if I can compose my cells with additional information, such as the color on the voxel, where the alpha channel keeps the state of the 1-bit cell.

Answer 1

Create a second texture and use it as a lookup table. In each 256x256 block of texture you can represent one logical operation, where the inputs are represented by a column / column and the output is represented by the texture value. In fact, in each RGBA texture, you can represent four logical operations in the 256x256 area. Beware of texture compression and MIP maps, though!