138 lines
5.8 KiB
Markdown
138 lines
5.8 KiB
Markdown
# CultMath
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Clean-room math shaped for people who think in HLSL.
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CultMath provides lowercase vector types, shader-style intrinsics, and native
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hot-path kernels so math-heavy renderer code can move between C#, Rust, and HLSL
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without turning every line into a translation exercise. It is not a
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Unity.Mathematics clone. It is a small, Aquarium-born library built from public
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shader semantics.
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## Current Surface
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- `float2`, `float3`, `float4`
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- component-wise arithmetic
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- scalar-to-vector splats
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- swizzles for common lanes
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- conversions to and from `System.Numerics`
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- `BatchMath` SoA kernels over `Span<float>` / `ReadOnlySpan<float>` using
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`System.Numerics.Vector<float>` when available, including radial falloff
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acceleration and semi-implicit Euler integration
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- `math` intrinsics: `radians`, `degrees`, `abs`, `floor`, `ceil`, `frac`,
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`min`, `max`, `clamp`, `saturate`, `lerp`, `step`, `smoothstep`, `dot`,
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`cross`, `length`, `distance`, `normalize`, `reflect`, `csum`, exponential
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`decay`/`damp`, intercept/segment helpers, Catmull-Rom, Bezier curves, and
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deterministic value-noise primitives
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- `shaders/CultMath.hlsl`, a canonical HLSL mirror include for shader-side
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parity. HLSL already owns `float2`, `float3`, and `float4`; the include
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exposes `cultmath_*` functions for shared semantics, including CultMath's
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safe `normalize` contract.
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- `Voronoi.SampleTones`, a C# batch surface that calls the Rust
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`cultmath-core` native kernel when `cultmath_core` is available and falls back
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to the managed parity path otherwise.
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- `PlanetaryField`, a scale-aware CPU/HLSL spherical field contract with
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deterministic identity, cube-sphere topology, residual pages, LOD residency,
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ray/path/region queries, coarse patches, and projected map-tile baking. See
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`docs/planetary.md`.
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- `CultMath.Unity`, an engine-facing assembly containing only Unity mesh and
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page-upload adapters for the canonical planetary contracts.
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## Native Core
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The canonical hot-path body lives in `native/cultmath-core`. It exports a C ABI
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for batch kernels such as `cultmath_apollonian_voronoi_tones`.
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Runtime wrappers own syntax and integration. Rust owns optimized primitive
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kernel behavior and parity fixtures.
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## Example
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```csharp
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using CultMath;
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float3 normal = math.normalize(new float3(0.25f, 1.0f, -0.1f));
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float rim = math.saturate(1.0f - math.dot(normal, new float3(0.0f, 0.0f, -1.0f)));
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float glow = math.smoothstep(0.2f, 1.0f, rim);
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float grain = math.value_noise_bicubic(math.float2(12.0f, 3.5f));
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```
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```hlsl
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#include "CultMath.hlsl"
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float3 normal = cultmath_normalize(float3(0.25, 1.0, -0.1));
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float rim = cultmath_saturate(1.0 - dot(normal, float3(0.0, 0.0, -1.0)));
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float glow = cultmath_smoothstep(0.2, 1.0, rim);
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float grain = cultmath_value_noise_bicubic(float2(12.0, 3.5));
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```
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## Provenance
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The small spline, damping, and pursuit helpers were promoted from Aetheria's
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local `AetheriaMath` surface. The value-noise family follows public shader
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literature from Inigo Quilez's noise and mini-spline articles, expressed in
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CultMath names with tests instead of copied project-local helper drift.
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The advanced erosion filter is an MPL-2.0 adaptation of Rune Skovbo Johansen's
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published filter. Its faithful planar core is isolated in
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`AdvancedErosionFilter.cs` and `AdvancedErosionFilter.hlsl`; spherical mapping
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is a separate CultMath concern. See `THIRD-PARTY-NOTICES.md`.
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## Build
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```powershell
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dotnet build CultMath.slnx
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dotnet test CultMath.slnx
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cargo test --manifest-path native/cultmath-core/Cargo.toml
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cargo build --release --manifest-path native/cultmath-core/Cargo.toml
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```
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## Unity compiler
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CultMath uses C# 10 record structs and file-scoped namespaces. Unity projects
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must select the compiler's latest language mode with an `Assets/csc.rsp` file:
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```text
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-langversion:latest
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```
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The package's Unity smoke project verifies this contract against Unity 6. The
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setting is already present in current GameCult Unity clients; it belongs to the
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consumer project because Unity only reads compiler response files from its
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`Assets` root.
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## Shader Tooling
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CultMath keeps portable DXC outside git under `.tools/`:
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```powershell
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.\tools\get-dxc.ps1
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.\tools\get-spirv-cross.ps1
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.\tools\compile-hlsl-spirv.ps1 `
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-ShaderPath E:\Projects\Odin\crates\muninn-move-tracker\shaders\MoveSphereCandidate.comp.hlsl `
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-OutputPath E:\Projects\Odin\crates\muninn-move-tracker\artifacts\shader\MoveSphereCandidate.comp.spv `
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-IncludePath E:\Projects\CultMath\shaders
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.\tools\compile-spirv-metal.ps1 `
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-SpirvPath E:\Projects\Odin\crates\muninn-move-tracker\artifacts\shader\MoveSphereCandidate.comp.spv `
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-OutputPath E:\Projects\Odin\crates\muninn-move-tracker\artifacts\shader\MoveSphereCandidate.comp.metal
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```
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DXC emits Vulkan SPIR-V with `-spirv`. `-TargetEnv vulkan1.2` is exposed by the
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script, but the current Windows DXC release compiled this shader successfully
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with DXC's default Vulkan target while rejecting the dotted target-env value.
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The SPIR-V script applies default Vulkan register shifts for cbuffers, textures,
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UAVs, and samplers so cross-compiled Metal buffers do not alias by resource
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class. SPIRV-Cross emits Metal Shading Language from SPIR-V on Windows; building
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an iPad-ready `.metallib` still belongs to Apple's Metal compiler on an Apple
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toolchain.
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## Doctrine
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The goal is mechanical sympathy between CPU-side authoring, native kernels, and
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GPU-side shader math. If an intrinsic exists here, it should behave like the
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shader concept unless a runtime's numeric rules make that impossible. Weird
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deviations get tests and documentation, not folklore.
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CultMath is still not a shader generator. Projects should include
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`shaders/CultMath.hlsl` directly or add that directory to their shader include
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path. If a shared operation needs CPU/GPU parity, put the primitive here and
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test it here before copying local math helpers into a renderer or daemon.
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