ply2vri

ply2vri is a simple command line tool for converting triangle meshes in PLY format into signed-distance volumetric grids in VRI format. This is particularly useful if you want to try out Stanford's Volfill hole-filling software.

Distribution

The current release is version 1.1. The zip file includes a Windows executable, source code, Visual Studio project file, and Linux makefile:

• ply2vri-1.1.zip (162 KB)
  In case something is terribly wrong with the latest version, here are the older versions:
• ply2vri-1.0.zip (153 KB)

Documentation

The command line parameters for ply2vri are:

ply2vri [<options>] <input file> [<output file>]

• .vri (or no ouput file given): The volumetric grid will be saved in Stanford's vrip format.
• .ppm: The volumetric grid will be saved in PPM image form, as a long strip of cross-sections (similar to the example output towards the bottom of this page).
• .raw: The raw unexpanded volumetric grid will be dumped in an undocumented format.

• -r: Specifies the voxel resolution, e.g., -r0.005 indicates that the edge length of each voxel will be 0.005 units in the PLY file's coordinate system.
• -l: Specifies the ramp length, e.g., -l5 indicates that 5 voxels in each direction from the surface will be marked. This optional parameter specifies the ramp length, i.e,., the number of voxels that will be marked in each direction from the surface. The distance from the surface is saved as an unsigned short (range 0 to 65535), so 32767 indicates a voxel located on the surface, 0 indicates a voxel located ramp_length * resolution outside the surface, and 65535 indicates a voxel located ramp_length * resolution inside the surface.

  ramp length = 5

  ramp length = 10

• -h: -h1 (the default) enables hard edges. This means that voxels whose closest surface point is at the boundary of the triangle mesh are marked as empty. -h0 will fill in the true signed distance to the surface, even at boundaries (note that the sign is poorly defined in some areas). Look at the hole in the bottom of the rabbit in this example:

  hard edges

  soft edges

• -s: Often the triangles near a hole are innaccurate and so you may want to throw them away. This optional parameter lets you specify how many times you want to remove all triangles that are adjacent to a hole, e.g., -s1 removes one layer of triangles from around the edge before scan converting.
• -a: The default algorithm (-a0) iterates over each triangle and splats in the distance for each voxel within a radius of the ramp length (similar to a z-buffer algorithm). -a1 uses an alternate algorithm that uses a KD-tree-like structure to find the closest point at each voxel. This second algorithm may be faster in some situations (especially if your ramp lengths are very long).
• -v: This option lets you specify a VRI file (e.g. -vfoo.vri) that will be used to provide space-carving information. The resolution and position of the voxel grid are extracted from the VRI file, and then after scan conversion any voxels marked as empty (value = 0, weight = 0) will be copied into the output.

Example

Below is an example of an input triangle mesh and the resulting volumetric distance field, displayed as a series of cross-sections:

License

This software is Copyright (c) 2002 University of Washington. Use at your own risk. The full license for this software can be found here: license.txt