cloth_step

Cloth integrate pass for the cloth module's GPU simulation. One thread per particle across every cloth in the shared domain: Verlet integration with gravity, gusty form-drag wind (force along the local surface normal), pinned particles anchored to their analytic grid position, and analytic collisions against a ground plane and up to four spheres per cloth. Also performs GPU-side (re)initialization of a cloth's grid when the reset param is set.