Fastest way to deal with many sprites in bevy-engine

Question

I am building a Cellular Automata visualization "game" with Rust and the BevyEngine. Currently, when initializing the world, I spawn a sprite for every cell. Within each update the sprites color is changed according to wether it is alive or dead.

for (grid_pos, mut color_mat)  in query.iter_mut() {
    let cell_state = world.0[grid_pos.1][grid_pos.0];

    match cell_state {
        0 => *color_mat = materials.dead_cell.clone(),
        1 => *color_mat = materials.alive_cell.clone(),
        _ => (),
    }
}

The thing is, when dealing with a larger and larger map, the number of sprites gets very high. So I wondered if it might be faster when I only spawn a sprite in the position of a living cell and remove it when the cell dies.

So my question is: Is it faster if I spawn all a sprite for every grid position OR is the better way to only spawn a sprite when a cell is alive and remove it when the cell dies.

Answer 1

I'm not familiar with Bevy's performance characteristics, but it is generally the case that to get good performance for drawing a cellular automaton, you don't want to be storing "sprite" objects for every cell, but an array of just the cell states, and drawing them in some kind of efficient batch form.

The state of of a cellular automaton is basically an image (possibly one with rather chunky pixels). So, treat it that way: copy the cell states into a texture and then draw the texture. If you want the cells to appear fancier than little squares, program the fragment shader to do that. (For example, you can read the CA-state texture and use it to decide which of several other textures to draw within the bounds of one square.)

This may or may not be necessary to get acceptable performance for your use case, but it will certainly be faster than managing individual sprites.