ReadonlybufferThe per-system instance buffer, allocated at the system's full capacity.
ReadonlycapacityFloats the buffer was allocated for — the system's capacity × 8.
The renderer frame ordinal of the last upload — the once-per-frame gate
(see the module header on the cadence deviation from GL). 0 on a fresh
record; the renderer's ordinal starts at 1.
Everything one particle system needs at draw time.