kyy13/mc-mesher

marching cubes mesh generator for c++, c#, and unity

mc-mesher

by Kyle J Burgess (github.com/kyy13)

Summary

mc-mesher is a lightweight marching cubes mesh generator for c, c++, c#, and Unity.

Features

details

Mesh Generation

• Generate 3D Marching Cubes meshes from a 3D scalar field and custom ISO level.
• Produces mesh indices, vertices, and normal vector data
• Choose between face normal vectors, and vertex normal vectors.

Algorithms

• Trace rays through a scalar field used to generate a mesh without requiring the mesh to be generated first; detects collision with the mesh and returns the point of intersection. This method will detect collision much faster than ray tracing implementations operating on the mesh data itself.

Performance

details

Notes

• mc-mesher is designed to produce indexed marching cubes meshes with minimal vertices.
• Meshes generated with face normals tend to be much larger due to the inability to index vertices that share the same position, because they have different normal vectors.
• Mesh generation functions have O(X*Y*Z) time complexity where X, Y, and Z refer to the dimensions of the scalar field used to produce the mesh.
• Meshes with face normals have O(1) temporary memory usage.
• Meshes with vertex normals have O(X*Y) temporary memory usage.

Quick Start

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Unity Steps

1. Download the latest release from the releases page.
2. Drop the DLL into the your Assets folder
3. Drop the mc_mesher.cs wrapper file into your Assets folder.

Build

details

Notes

• There are precompiled binaries available on the releases page.
• See the build scripts in the scripts folder for examples on how to build with cmake.
  The scripts are setup to target mingw-w64 for 64-bit windows.

Requirements

1. A working c++17 (or higher) compiler.
2. CMake version 3.7 or higher

Steps

1. Run cmake with DCMAKE_BUILD_TYPE=Release to generate the build files
2. Run make to compile

mc-mesher uses lookup tables modified from the transvoxel algorithm [1].

[1] Lengyel, Eric. “Voxel-Based Terrain for Real-Time Virtual Simulations”. PhD diss., University of California at Davis, 2010.

mc-mesher's Issues

reduce temp cache size

alternate between cache maps for each z coordinate, in order to avoid huge memory cost for generating a mesh.

test for vertex uniqueness in vn meshes

set unity mesh bounds manually instead of Recalculate bounds

small performance optimization

add virtual mesh contains point method

unity example update

should probably take a ref to Mesh instead of a MeshFilter for generate functions

does cache need to store v and n?

should be able to get away with just storing indices

mesh generator flags

MCM_VERTEX_NORMALS
MCM_FACE_NORMALS (use face instead of vertex)

MCM_WINDING_RHCS_CCW
MCM_WINDING_RHCS_CW
MCM_WINDING_LHCS_CCW
MCM_WINDING_LHCS_CW

MCM_VERTEX_EDGE_LERP

and a function that takes bytes instead of floats

McmGenerateMesh
McmGenerateMesh_U8

also add segment-intersect-mesh for early out detection

McmMeshIntersectsSegment()
McmMeshIntersectsSegment_U8()
McmMeshIntersectsRay()
McmMeshIntersectsRay_U8()

and contains point method...

McmMeshContainsPoint()
McmMeshContainsPoint_U8()

and cleanup function to clean clean a scalar field of voxel noise that isn't part of the surface. (optimize for compression)

McmCleanEmptyVoxels()
McmCleanEmptyVoxels_U8()

Add link to PHD paper in README

remove unused mcmComputeEdgeCacheKey

Implement IDisposable to c# interface

IDisposable is made for freeing unmanaged respurces.

https://docs.microsoft.com/en-us/dotnet/api/system.idisposable

change examples to wrappers

cleanup

exceptions: use throw enum.ToString()

enums: set explicit enum types

ray intersection flags

for optionally including aabb intersection from inside or outside or both

update build scripts

has personal paths and artifacts from previous sdl2 project... needs to be cleaned up and probly changed to *.bat

add dll toggle for unity platform

https://stackoverflow.com/questions/10852634/using-a-32bit-or-64bit-dll-in-c-sharp-dllimport

https://docs.unity3d.com/560/Documentation/Manual/PlatformDependentCompilation.html

vn optimization

separate meshgen vn function, so that memBoundedOffets don't need to be recalculated in every iteration

edge identifier

mcmGenerateUniqueEdgeID(uniqueVertexID, vertexData)

where uniqueVertexID is calculated incrementally in main loops

ray intersection aabb

ray cast returns no intersection when positioned outside of mesh aabb. it should step ray to edge, then continue ray casting instead.

pictures for vn and fn

remove unity skybox and provide simple color shader for vn and fn mesh