v0.0.3

Other

• Round 188: curv2 2D trimming-curve tessellation
• Round 182: basis-matrix surf surface tessellation
• Round 14: Taylor polynomial surf surface tessellation
• Round 14 (depth): cargo-fuzz harness + two parse-time panic fixes

Added

• 2D trimming-curve (curv2) tessellation under
  ObjDecoder::with_curve_tessellation(samples: u32). The decoder now
  evaluates every curv2 directive — the parameter-space curve used as
  an outer / inner trimming loop, a special curve, or for connectivity
  (spec §"curv2") — into a Topology::LineStrip polyline on a new
  synthetic mesh named "obj:curves2". A curv2 references vp
  parameter vertices (spec §"vp u v w") and lies in the 2D parameter
  space of the surface it trims, so each vp (u, v) is lifted into a
  [u, v, 0.0] control point and run through the same Bezier /
  B-spline / Cardinal / Taylor / basis-matrix evaluators the 3D curv
  path uses; the sampled x/y are the parameter-space coordinates and
  z stays 0.0. Unlike curv, a curv2 line carries no inline
  u0 u1 range — the B-spline evaluation window is taken from the
  block's parm u knot vector ([parm_u[0], parm_u[last]]). The
  optional 3rd vp coordinate is the rational weight (default 1.0; a
  stored 0.0 — the vp padding default — is read back as 1.0 for
  the rational forms since a zero weight is degenerate). Negative
  curv2 indices resolve relative-from-end against the vp pool (spec
  §"Special point" example curv2 -6 -5 …). Synthetic primitives carry
  the shared obj:tessellated_curve sentinel (so the encoder filters
  them out and replays the original cstype / curv2 / end block
  verbatim from Scene3D::extras["obj:freeform_directives"]) plus a
  obj:curve2 = true marker and the
  obj:curve_kind / obj:curve_degree / obj:curve_u_range /
  obj:curve_samples provenance. Malformed curv2 blocks (missing
  cstype, missing knot vector for B-spline, fewer than two control
  points, out-of-range vp indices) are silently dropped. The
  trim / hole / scrv statements that reference these curves by
  index still ride on freeform_directives verbatim — surface clipping
  against the loops remains future work.
• Basis-matrix surf surface tessellation under
  ObjDecoder::with_curve_tessellation(samples: u32). The decoder now
  evaluates surf elements that sit under a cstype bmatrix (or
  cstype rat bmatrix) header into a triangulated Topology::Triangles
  primitive on the synthetic "obj:surfaces" mesh, via the bivariate
  tensor-product polynomial
  S(u, v) = Σ_a Σ_b (Σ_p B_u[a][p] · u^p) (Σ_q B_v[b][q] · v^q) · c_{base_u + a, base_v + b} (spec §"Basis matrix",
  §"bmat u/v matrix", §"step stepu stepv"). Per-direction basis
  matrices come from bmat u / bmat v (row-major, column index
  varying fastest); per-direction segment strides come from
  step stepu stepv. The per-direction control-grid extent is the
  inverse of the spec relation parm = (K − n) / s + 2, i.e.
  K = (parm − 2) · s + n + 1, applied independently in u and v per
  spec §"step stepu stepv" ("For surfaces, the above description
  applies independently to each parametric direction."). Multi-patch
  grids are now decomposed into (K_u − n − 1) / stepu + 1 × (K_v − m − 1) / stepv + 1 polynomial segments; the global parameter (u, v) partitions into per-segment (seg_u, seg_v, t_u, t_v) with the
  patch-local control window starting at (seg_u · stepu, seg_v · stepv). The cubic Bezier basis-matrix surface from the spec
  §"Examples" reproduces the equivalent cstype bezier patch sample-
  for-sample on its single-patch form. The rat bmatrix qualifier
  routes to the same evaluator without per-vertex weight blending
  (matches the round-10 1D curve behaviour — the user's basis is the
  authoritative source). Malformed blocks (missing bmat u / bmat v,
  missing step, wrong-size matrices, mismatched control-vertex
  count) are silently dropped — the directive sequence still rides on
  Scene3D::extras["obj:freeform_directives"] for round-trip.
  Synthetic primitives carry obj:tessellated_surface = true,
  obj:surface_kind ("bmatrix"), obj:surface_degree,
  obj:surface_u_range, obj:surface_v_range, and
  obj:surface_samples provenance plus the shared
  obj:tessellated_curve = true sentinel so the encoder filters the
  synthetic geometry out and replays the original
  cstype / deg / bmat u / bmat v / step / parm u /
  parm v / surf / end block verbatim. Trim/hole loop
  evaluation remains out of scope.
• Taylor polynomial surf surface tessellation under
  ObjDecoder::with_curve_tessellation(samples: u32). The decoder now
  evaluates surf elements that sit under a cstype taylor (or
  cstype rat taylor) header into a triangulated Topology::Triangles
  primitive on the synthetic "obj:surfaces" mesh, via the bivariate
  tensor-product Horner-rule evaluation
  S(u, v) = Σ_i Σ_j c_{i,j} · u^i · v^j (spec §"Taylor"). Control
  points are the polynomial coefficients in spec §"Surface vertex data
  — control points" row-major u-fastest order; a single Taylor patch
  of declared degree deg degu degv needs exactly
  (degu + 1) × (degv + 1) coefficient vectors. The surf s0 s1 t0 t1
  range supplies the global parameter clip; Taylor surfaces evaluate
  against the raw [s0, s1] × [t0, t1] window directly (not a
  normalised [0, 1] re-parameterisation). The implementation
  collapses the inner u sum via Horner's rule across each v-row, then
  a second Horner-rule pass in v over the collapsed points; total
  surface sample count is (samples + 1)². The spec note in
  §"Free-form curve/surface body statements" says the rational form
  "does not make sense for Taylor", so rat taylor routes to the same
  evaluator without per-vertex weight blending. Synthetic primitives
  carry obj:tessellated_surface = true, obj:surface_kind
  ("taylor"), obj:surface_degree, obj:surface_u_range,
  obj:surface_v_range, and obj:surface_samples provenance plus the
  shared obj:tessellated_curve = true sentinel so the encoder filters
  the synthetic geometry out and replays the original
  cstype / deg / surf / parm / end block verbatim from
  Scene3D::extras["obj:freeform_directives"]. Basis-matrix surf
  surfaces remain captured-only.