directxmesh-usage

name	directxmesh-usage
description	Guide for integrating the DirectXMesh geometry processing library into a C++ project.
license	MIT
metadata	{"author":"chuckw","version":"1.0"}

DirectXMesh Usage Guide

This skill provides guidance for integrating the DirectXMesh geometry processing library into a C++ project.

When to Use

Invoke this skill when:

• Adding DirectXMesh as a dependency to a new or existing project.
• Writing code that processes mesh geometry (normals, tangents, optimization, meshlets).
• Needing to understand the typical DirectXMesh processing pipeline.

Overview

DirectXMesh is a geometry processing library for Direct3D 11 and Direct3D 12 applications. It provides support for loading and saving mesh data, and performing various geometry processing operations including normal and tangent computation, adjacency generation, and mesh optimization.

• Repository: https://github.com/microsoft/DirectXMesh
• Documentation: https://github.com/microsoft/DirectXMesh/wiki
• NuGet Packages: directxmesh_desktop_win10, directxmesh_uwp
• vcpkg Port: directxmesh

Integration Methods

vcpkg manifest-mode (Recommended)

In your vcpkg.json file, add the following:

{
  "$schema": "https://raw.githubusercontent.com/microsoft/vcpkg-tool/main/docs/vcpkg.schema.json",
  "dependencies": [
    "directxmesh"
  ]
}

vcpkg (classic)

vcpkg install directxmesh

Features: dx12 (DirectX 12 input layout support), tools (command-line tools). Triplets: x64-windows, x64-linux, arm64-windows, etc.

For DLL usage (x64-windows default triplet), define DIRECTX_MESH_IMPORT in your consuming project. For static library usage, use -static-md triplet variants.

CMakeLists.txt:

find_package(directxmesh CONFIG REQUIRED)
target_link_libraries(${PROJECT_NAME} PRIVATE Microsoft::DirectXMesh)

NuGet

Use directxmesh_desktop_win10 for Win32 desktop applications or directxmesh_uwp for UWP apps.

Project Reference

Add the appropriate .vcxproj from the DirectXMesh/ folder to your solution and add a project reference. Add the DirectXMesh directory to your Additional Include Directories.

Header Usage

#include <d3d12.h>        // or <d3d11_1.h> — include BEFORE DirectXMesh.h
#include "DirectXMesh.h"

using namespace DirectX;

All functions reside in the DirectX namespace. Most functions have overloads for both 16-bit and 32-bit index buffers.

Typical Processing Pipeline

flowchart TD
    A[Load geometry\npositions, indices, texcoords] --> B
    B[GenerateAdjacencyAndPointReps] -->|adjacency, pointRep| C
    C[Validate\noptional diagnostics] --> D
    D[Clean\nfix bowties, degenerate triangles] -->|dupVerts| E
    E[ComputeNormals / ComputeTangentFrame] --> F
    F[AttributeSort] -->|faceRemap| G
    G[OptimizeFaces] -->|faceRemap| H
    H[ReorderIB\napply face remap] --> I
    I[OptimizeVertices] -->|vertexRemap| J
    J[FinalizeIB + FinalizeVB\napply vertex remap and dupVerts] --> K
    K[CompactVB\noptional, remove trailing unused vertices] --> L
    L[ComputeMeshlets] -->|"meshlets, uniqueVertexIB (uint8_t), primitiveIndices"| M
    M[ComputeCullData\nfor mesh shader GPU culling]

Note: uniqueVertexIB from ComputeMeshlets is a packed buffer of uint16_t or uint32_t indices (matching the original IB format). Reinterpret-cast it to the appropriate type for ComputeCullData.

Error Handling

• Most functions return HRESULT. Check with SUCCEEDED(hr) or FAILED(hr).
• Functions marked noexcept never throw; they return E_OUTOFMEMORY or E_INVALIDARG on failure.
• Functions using std::vector or std::function may throw on allocation failure

Key References

• Public API header: DirectXMesh/DirectXMesh.h — read this for exact signatures and SAL annotations.
• API overview table: See reference/overview.md in this skill folder.
• Wiki documentation: https://github.com/microsoft/DirectXMesh/wiki
• Utility headers: Utilities/WaveFrontReader.h (OBJ file loading), Utilities/FlexibleVertexFormat.h (legacy FVF conversion).

Platform Notes

• Windows desktop (Win8.1+), UWP, Xbox (GDK), and Linux are supported.
• Non-Windows builds require the DirectX-Headers package and define USING_DIRECTX_HEADERS.
• The library requires C++17 to build but the public API is C++11 compatible.

Further Reading

• Getting Started
• DirectXMesh Wiki
• API Reference