run method

@override Vector4? run(Float32List v, ShaderBindings bindings, FragmentContext c)

Returns linear RGBA for attachment zero. Null discards the fragment.

Implementation

@override
Vector4? run(Float32List v, ShaderBindings bindings, FragmentContext c) {
  final source = bindings.textures['static_shadow_texture'];
  if (source == null) return null;
  final tile = bindings.vec4('ShadowCopyInfo', 'tile', Vector4.zero());
  final shift = bindings.vec4('ShadowCopyInfo', 'shift', Vector4.zero());
  final fromU = v[0] - shift.x;
  final fromV = v[1] - shift.y;
  final inside = fromU >= 0.0 && fromU <= 1.0 && fromV >= 0.0 && fromV <= 1.0;
  final stored = source
      .sample(
        tile.x + fromU.clamp(0.0, 1.0) * tile.z,
        tile.y + fromV.clamp(0.0, 1.0) * tile.w,
      )
      .x;
  // Nothing stays nothing: the far end is not a depth the move shifts. One
  // the ordinary way round, nought turned round, and mode two writes the
  // turned map back the ordinary way — `A2.8`, as `shadow_copy.frag`.
  final mode = shift.w;
  final nothing = mode > 0.5 ? 0.0 : 1.0;
  final moved = inside && stored != nothing
      ? (stored + shift.z).clamp(0.0, 1.0)
      : nothing;
  final depth = mode > 1.5 ? 1.0 - moved : moved;
  c.fragDepth = depth;
  return Vector4(depth, 0.0, 0.0, 1.0);
}