Module gpu_density 

GPU density entities: a figure described by a handful of bones, rendered as millions of particles that never touch the CPU.

A GpuDensityEntityData is sixteen capsules with a radius, a density weight and a colour, plus a few numbers about how the whole body behaves: how much of it is still bound (hp), how it breathes, how tightly its matter holds to the skeleton. That is all that crosses to the GPU each frame: under a kilobyte.

Every particle is then derived in the vertex shader from its own instance index. A hash picks a bone in proportion to the bones’ weights, a point in that capsule, a phase for its jitter, and whether it is one of the ones that has come loose. Nothing is stored per particle, nothing is uploaded, and the count is whatever the GPU can draw: two million particles is one instanced draw call of two million quads.

Loose matter drifts away from the body and fades. Lower hp and more of the body is loose, which is what damage looks like on something that is made of matter rather than drawn.

This needs nothing past OpenGL 3.3: no compute, no storage buffers.

Structs

GpuBone

One capsule of the skeleton, laid out for the shader.

GpuDensityEntityData

Everything the GPU needs to draw one entity this frame.

GpuDensityRenderer

The GL side: one program, one quad, no per-particle data at all.

Constants

MAX_BONES

The number of bones an entity carries. Fixed so the whole skeleton fits in one uniform array.

MAX_PARTICLES_PER_ENTITY

The most particles one entity is ever drawn with, whatever was asked for. Above this the draw is fill-bound on any GPU and the picture stops improving, because there are more particles than pixels.

Functions

particle_alpha

The alpha of one particle, so that a body of any count sums to about the same brightness.

particle_pixels

The size of one particle on screen, in pixels, for a count. Fewer particles are drawn bigger so the body still reads as solid.