Expand description
Custom-shape (shapecode_N) phase of the engine update loop.
For every enabled shapecode_N block, runs the pre-compiled init (once
per preset load) and per-frame blocks once per instance, packs the
resulting state into a CustomShapeInstance storage buffer, and returns
the instance + batch streams. The renderer expands each instance into
a triangle fan on the GPU — one draw call per shape. Caller pushes the
result to the correct chain (primary for current, secondary for
fading_out during a preset transition).