At spawn, init_particle() samples its fixed properties from a
deterministic PRNG into s3de_particle, so playback is reproducible.
Each frame, update_object_states() interpolates the emitter's animated
properties into s3de_object_state.
To draw, render_s3de_effect() combines the two: for each live particle
s3de_billboard_world_transform() or s3de_mesh_world_transform() derives
a world matrix from the lifetime state computed by eval_particle(),
together with a posture basis that orients the quad or mesh. Objects are
drawn sorted by distance from the camera.
kichikuou
847987ec1b