LOG.md

Progress Log

Particle Attribute Update via Texture

I've successfully packed my data as textures and have managed to read and modify it at least mostly correctly.

Currently I'm packing all particle data into a single texture, where one pixel is used for the position and one pixel is used for the velocity. MAC grid data is stored in two textures. One stores U, V, W velocities, and pressure. The other stores the old U, V, W velocities and grid cell type.

For particle attribute updates, most work so far is in the vertex shader. Applying gravity only involves rendering a quad the size of the velocity texture and appropriately decrementing the V velocity. I update particles by simply rendering an attribute array of consecutive numbers. These serve as indices into the particle texture. After doing somewhat tedious index calculations, I can extract the position and velocity for that particle. I can then lookup velocities in the grid textures to update the particle. Something I did not anticipate at first was that I need to have two particle buffers and ping-pong them because you cannot write to the same texture from which you are reading.

Here's an interesting blooper. I currently have no pressure solve so nothing prevents the particles from going out of bounds. If that happens, they do really weird things.