Uniform Path Drop Cutter

This spec defines fixed-spacing projection of line and arc paths onto a mesh.

Purpose

Uniform path drop-cutter samples source paths at predictable intervals and runs batch drop-cutter on those samples. It is simpler than adaptive projection and useful for debugging, deterministic tests, and coarse previews.

Dependencies

• Line and Arc Path Spans
• Batch Drop Cutter

Inputs

type UniformPathDropInput = {
  paths: Array<{ id: string; spans: SerializedCamSpan[] }>;
  cutter: CamCutter;
  triangles: CamTriangle[];
  sampleSpacing: number;
  floorZ: number;
  preserveSpanBoundaries?: boolean;
};

Output

type UniformPathDropOutput = {
  paths: Array<{
    id: string;
    points: CamCLPoint[];
    sourceSpanIds: string[];
  }>;
  warnings: string[];
  summary: {
    sourcePathCount: number;
    spanCount: number;
    sampleCount: number;
  };
};

Algorithm

1. Validate sampleSpacing > 0.
2. Deserialize spans.
3. For each source path:
   • Initialize an empty sample list.
   • For each span:
     • Compute steps = max(1, ceil(span.length2d() / sampleSpacing)).
     • Sample span.pointAt(i / steps) for i = 0..steps.
     • Initialize sample Z to floorZ.
     • Avoid duplicating the previous span endpoint unless preserving span boundary.
   • Store mapping from samples to span ids.
4. Flatten all samples for batch drop-cutter.
5. Run batch drop-cutter once for all samples.
6. Re-split projected points back into source paths.

Boundary Rules

• Preserve path boundaries.
• Preserve first and last point of every source path.
• If a span is degenerate, skip it and warn.
• If all spans in a path are degenerate, return no generated path for that source path.

Progress Phases

• uniform-path-sample
• uniform-path-drop
• uniform-path-rebuild

Tests

• A line of length 10 with sample spacing 2 emits 6 samples including endpoints.
• Arc samples remain on the source circle before projection.
• Adjacent spans do not duplicate shared endpoints by default.
• Projected path retains source path ids.
• Degenerate span warning is deterministic.