Math libraries: BCL-first, no dimension suffixes

name: Math libs BCL refactor overview: Refactor novolis-math into BCL-first, dimension-suffix-free public APIs (Ray, Sphere, AxisAlignedBox), extract Novolis.Math.Topology, centralize intersection/BVH in Geometry, then update Physics/Rendering consumers and governance docs in a coordinated NuGet publish wave. todos:

• id: docs-naming-policy

content: Update novolis-math/docs/design.md and library-boundaries.md with facet DAG, no 3/2D public API rule, and Ray/Sphere/AxisAlignedBox names status: completed

• id: topology-package

content: Create Novolis.Math.Topology project; move Polygon/Edge/Face/Shape + factories; Geometry references Topology; slnx + tests status: completed

• id: rename-primitives

content: Rename Ray3/Sphere3/AxisAlignedBox3 to Ray/Sphere/AxisAlignedBox in math and all consumers (no obsolete Ray3 public type) status: completed

• id: intersection-bvh-api

content: Public AxisAlignedBox.RayInterval + BvhRaycast; refactor TriangleBvh to use shared traversal; add parity unit tests status: completed

• id: pose-helpers

content: Add RigidTransform and ViewBasis; obsolete mutable Transform; remove unused Math.Camera and Math.Grid if unreferenced status: completed

• id: physics-consolidate

content: BvhStaticWorld uses TriangleBvhBuilder + shared raycast; delete Physics TriangleRay duplicate; update ObsoleteNumerics messages status: completed

• id: rendering-consolidate

content: Unify BvhNode with TriangleBvhNode; PathTracerEngine uses Math traversal; CameraSnapshot uses ViewBasis on host status: completed

• id: cross-repo-sweep

content: Update simulation, dogfooding DoomLite3D, Directory.Packages.props, templates; verify-nuget-only + build/test + pack publish wave status: completed isProject: false

North star

Math owns spatial algorithms on `System.Numerics`, in small facets. Public API rules:

• BCL types at the surface (Vector3, Quaternion, Matrix4x4, Plane).
• No `*3` / `*2D` suffixes on public Math types or members (stack is 3D-only; planar work uses Vector3 with Y = 0 via `Vector3PlanarExtensions.cs`).
• No `Vector2` in stack code (existing governance).
• No obsolete public shims named `Ray3` — breaking rename in one wave (avoid perpetuating forbidden names).

Backend-only duplicates (Float3 in ILGPU) stay in `Novolis.Rendering.Backends.Igpu`.

flowchart BT
  Arrays[Novolis.Math.Arrays]
  Topology[Novolis.Math.Topology]
  Geometry[Novolis.Math.Geometry]
  Topology --> Arrays
  Geometry --> Arrays
  Geometry --> Topology
  Physics[Novolis.Physics.*]
  Rendering[Novolis.Rendering.*]
  Physics --> Geometry
  Rendering --> Geometry

Phase 1 — Governance and math design docs

Update canonical policy so agents and consumers match implementation:

Add a short naming table (single source of truth):

Files to rename in Geometry: `Ray3.cs` → Ray.cs, `Sphere3.cs` → Sphere.cs, `AxisAlignedBox3.cs` → AxisAlignedBox.cs.

Phase 2 — Extract `Novolis.Math.Topology`

New project: src/Novolis.Math.Topology/Novolis.Math.Topology.csproj (packable, net10.0, no deps except BCL).

Move from Geometry (namespace Novolis.Math.Topology):

• Connectivity: `Polygon.cs`, `Edge.cs`, `Face.cs`, `Shape.cs`
• Factories/extensions: PolygonFactory*, ShapeFactory, FaceFactory, *Extensions for polygon/shape/face/edge

Keep in Geometry (metric / queries):

• `TriangleMesh.cs`, primitives, transforms, intersection, BVH, lattice types, Rgba32, serializers

Wire solution: `Novolis.Math.slnx` + `Directory.Packages.props`.

Geometry csproj: ProjectReference → Topology (Topology does not reference Geometry).

Move tests: PolygonTest, PolygonFactoryTests → tests/Novolis.Math.Unit/Topology/.

Phase 3 — Centralize intersection and BVH in Geometry

Today `TriangleBvh.cs` keeps RaySlabIntersect private while `PathTracerEngine.cs` and `BvhStaticWorld.cs` duplicate ~80 lines each.

Add public APIs (names without dimension suffix):

1. `AxisAlignedBox.RayInterval` (or static RayExtensions.IntervalAgainstBox) — slab test used by BVH and shadow rays.
2. `TriangleBvhNode` — already suffix-free; keep as the single node struct.
3. `TriangleBvhBuilder.Build` — unchanged entry; returns TriangleBvh.
4. `BvhRaycast` (static helper) — traverse ReadOnlySpan<TriangleBvhNode> + triangleOrder + callback bool TryHitTriangle(int triIndex, in Ray ray, float maxT, out float t, out Vector3 normal) so material index lives in the callback (Rendering) while Physics uses triangle index only.

Refactor `TriangleBvh.Raycast` to call shared traversal internally.

Add unit tests: brute vs BVH parity, analytic ray–box, ray–triangle edge cases; shared epsilon via small GeometryConstants type.

Phase 4 — BCL-centric pose helpers (no camera types)

Add (Geometry, System.Numerics only):

• `RigidTransform` — readonly struct with Vector3 Position, Quaternion Rotation, float UniformScale; ToMatrix4x4(), TransformPoint/TransformDirection.
• `ViewBasis` — FromLookAt(eye, target, upHint) → orthonormal (Forward, Right, Up); `PrimaryRayDirection(basis, u, v, tanHalfFov, aspect)` for trace kernels.

Do not add RigidTransform3, ViewBasis3, or new Camera types.

Remove unused obsolete surface from Geometry if unreferenced after grep: `Camera.cs`, `Grid.cs` (Simulation already uses `DenseGrid<T>`).

Mark mutable `Transform` class [Obsolete("Use RigidTransform")]; keep for one release if templates still reference it, then migrate callers.

Phase 5 — Physics consolidation

Physics packages already reference Geometry only — no new Topology reference unless a project uses Polygon directly.

Phase 6 — Rendering consolidation

Out of scope: moving GGX/glass/sky into Math (Rendering-only).

Phase 7 — Cross-repo consumer sweep

Mechanical rename in all .cs referencing old types (~25 files today):

• novolis-physics (abstractions, collision, ballistics, tests)
• novolis-rendering (compile, runtime, CPU backend)
• novolis-simulation (`PlanarAgent.cs`, builder tests)
• `DoomLite3D/PlayerController.cs` — delete local Ray3 struct; use Novolis.Math.Geometry.Ray

Bump central package versions where needed:

• `novolis-math/Directory.Packages.props` — add Novolis.Math.Topology
• `novolis-physics/Directory.Packages.props`, `novolis-rendering/Directory.Packages.props`, `novolis-simulation/Directory.Packages.props`, `novolis-dogfooding/Directory.Packages.props` if explicit pins exist

MonoGame template content referencing Polygon may need PackageReference to Topology or Geometry (transitive).

Phase 8 — Verification and publish

Per workspace rule (`nuget-only-dependencies`):

1. pwsh -File novolis-governance/scripts/verify-nuget-only.ps1 (exit 0)
2. dotnet build / dotnet test `Novolis.Math.slnx`, then Physics + Rendering solutions
3. Local pack feed or GPR publish Novolis.Math.Arrays, Novolis.Math.Topology, Novolis.Math.Geometry (2026.1.*)
4. dotnet restore + dotnet build consumers with package refs only

Breaking change note: no public Ray3 obsolete alias (forbidden name). Release notes list rename table and Topology package install (dotnet add package Novolis.Math.Topology only when using polygon APIs directly; Geometry consumers get Topology transitively).

Risk notes

• `Ray` name: lives in Novolis.Math.Geometry namespace — no BCL Ray conflict; avoid using aliases that pull in unrelated Ray types.
• ILGPU: device code may keep duplicated slab/triangle until a shared-source or codegen step exists; CPU/Physics path must be single implementation.
• Coordinate publish order: Math packages first, then Physics/Rendering PRs that bump PackageReference versions.