This post is out-of-date. Check out V-HACD 2.0!

**V**-HACD: Hierarchical Approximate Convex Decomposition Revisited

Lately, I have found time to work on improving the HACD algorithm. The new

**V**-HACD library tries to tackle the problem of convex-hulls inter-penetration usually encountered when using HACD. Figure 1 illustrates this limitation by comparing V-HACD results to those generated by using HACD.
Figure 1.

**V**-HACD vs. HACD:**V**-HACD generates non-overlapping convex-hulls.
V-HACD works only with manifold closed meshes of arbitrary genus, which makes it less general than HACD algorithm (which handles open and non-manifold meshes). The V-HACD code is available under New BSD License. However, the current version relies on the following other libraries:

The first results are encouraging. However, the code is still buggy and not optimized. I hope that people would be interested in helping me improve this first version.

- Triangle to compute constrained delaunay triangulation which has a non permissive license, which should be replaced [Thanks to Erwin Coumans for noticing that]
- Ole Kniemeyer's implementation of the convex-hull algorithm provided with bullet
- John Tsiombikas's kd-tree algorithm

The first results are encouraging. However, the code is still buggy and not optimized. I hope that people would be interested in helping me improve this first version.

To play with the algorithm, a pre-compiled win32 executable is available here

Pre-computed decomposition results are available here

Pre-computed decomposition results are available here

V-HACD parameters are the following:

testVHACD fileName.off depth maxConcavity invertInputFaces posSampling angleSampling posRefine angleRefine alpha targetNTrianglesDecimatedMesh

- fileName.off: 3D mesh in off format (type: string, example: block.off )
- depth: maximum number of decomposition stages (type: integer, default: 10)
- maxConcavity: maximum allowed concavity (type: float, default 0.01)
- invertInputFaces: indicates whether mesh normals should be inverted or not (type: boolean, default 0)
- posSampling: clipping plane position sampling resolution for coarse search (type: int, default 10)
- angleSampling: clipping plane orientation sampling resolution for coarse search (type: int, default 10)
- posRefine: clipping plane position sampling resolution for refined search (type: int, default 5)
- angleRefine: clipping plane orientation sampling resolution for refined search (type: int, default 5)
- alpha: parameter controlling the compromise between concavity and balance between convex-hulls. (type: float, default: 0.01)
- targetNTrianglesDecimatedMesh: number of triangles in the decimated mesh. V-HACD decimates the input mesh to reduce computation times. (type: integer, default: 1000)

To apply V-HACD to the input mesh "input.off" use the following command line:

testVHACD.exe input.off 30 0.01 0 64 32 8 64 0.001 2000

The current version of V-HACD provides poor results or errors for the following three meshes. As soon as I get some free time I'll try to fix these bugs.

- dancer2
- elk
- hand1
- hand2
- hero
- octopus
- polygirl
- shark_b
- Sketched-Brunnen
- torus
- tstTorusModel
- tstTorusModel3

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