ADR-0005: Half-Edge Padding Strategy

Status

Proposed

Context

JAX requires static shapes for jit compilation. Topological data structures (half-edge meshes) have dynamic sizes that change with Boolean operations. A strategy is needed to represent variable-topology meshes within JAX's static shape constraint.

Decision

Use padding with masking:

• Allocate fixed-capacity arrays for vertices, edges, and faces
• Use boolean mask arrays to indicate valid (non-padding) elements
• Capacity is set at construction time based on expected maximum complexity
• Operations that exceed capacity raise a clear error rather than silently truncating

Consequences

• Memory overhead from padding (acceptable for typical CAD complexity)
• All topology operations must respect masks (adds implementation complexity)
• No need for pure_callback or escaping jit for topology changes