TexMetro

A tool for evaluating a number of quality metrics on textured 3D models. It computes a number of measures on arbitrary user provided photo-reconstruction models. This tool can be used to assess and compare existing or future alternative photo-reconstruction tools (e.g. starting from the same set of images), as well as to assess the efficacy of existing or future methods aimed to improve the quality of the texturing of 3D models.

The UV-map, geometry, and connectivity of the an input models are analyzed. The statistics in full are collected in a JSON file while only a relevant subset of them is displayed on the standard output, consisting of salient information about the mesh geometry, its parameterization and texture data. A description of the JSON file structure can be found below.

The tool is used to compute the statistics shown in the benchmark Real-World Textured Things

A few of the measures are dependent on the texture resolution (in texels). In order to compute these, TexMetro takes as input the actual texture image, or, simply, its dimensions, provided as command-line arguments. The TexMetro tool is OpenSource and is implemented in C++ using vcg library for mesh processing, Qt (for and image loading and interfacing), and OpenGL (to accelerate texture overlap detecting, which is implemented by rasterization over off-screen buffers)

Usage

Texmetro supports OBJ, PLY and FBX 3D models. To compute the metrics for a given model simply run

texmetro path/to/model.obj

By default, texmetro creates a JSON output file named texmetro.json. You can use the -j --json option to specify a custom name:

texmetro path/to/model.obj --json model_data.json

If your model has texure coordinates but no actual texture data, you can use the -t --texsize option to specify a virtual texture size that will be used to compute the texture-related metrics (with the exception of the seam color discrepancy, for obvious reasons):

texmetro path/to/model_without_texture.obj -t 2048x1024

Metrics and JSON format

The JSON file contains a single object that encoding a dictionary of all the metrics computed by TexMetro. The structure of the object is for the most part straightforward.

General mesh-related metrics

Entry	Description
mesh	The name of the mesh file
fn	Number of faces
vn	Number of vertices
en	Number of edges
en_b	Number of boundary edges
area	Surface area
boundary_len	Boundary length
area_normalized	Normalized surface area (max bounding box side equal to 1)
boundary_len_normalized	Normalized boundary length (max bounding box side equal to 1)
boundary_loops	Number of boundary loops
nonmanif_edge	Number of non-manifold edges
nonmanif_vert	Number of non-manifold vertices
connected_components	Number of connected components
genus	Surface genus
fndup	Number of duplicated faces
fnzero	Number of zero-area faces
fndegen	Number of degenerate faces (non 3-simplexes)
vnunref	Number of unreferenced vertices
oriented	Mesh is coheriently oriented (bool)
orientable	Mesh is orientable (bool)

UV and texture related metrics

Entry	Description
num_charts	Number of UV charts
en_uv	Number of UV edges
en_uv_b	Number of UV boundary edges
area_uv	UV area
boundary_len_uv	UV boundary length
num_null_charts	Number of charts with zero UV area
mapped_fraction	Fraction of the 3D surface that is UV mapped
nfolds	Number of inverted UV triangles (an inverted triangle is a triangle whose signed area does not agree with the signed area of its chart)
ntex	Number of texture files
textures	List of texture file names
texture_N	List of raster stats for texture N at various MIP levels (see Raster statistics below for details)
occupancy	Fraction of the available texture area that is mapped to the 3D surface
seam_discrepancy_avg	Average seam color discrepancy (weighted by 3D edge length)
seam_discrepancy_min	Minimum seam color discrepancy
seam_discrepancy_max	Maximum seam color discrepancy
seam_discrepancy_stddev	Seam color discrepancy standard deviation
qcd_perc1	Quasi-conformal distortion 1st percentile
qcd_perc10	Quasi-conformal distortion 10th percentile
qcd_perc20	Quasi-conformal distortion 20th percentile
qcd_perc30	Quasi-conformal distortion 30th percentile
qcd_perc40	Quasi-conformal distortion 40th percentile
qcd_perc50	Quasi-conformal distortion 50th percentile
qcd_perc60	Quasi-conformal distortion 60th percentile
qcd_perc70	Quasi-conformal distortion 70th percentile
qcd_perc80	Quasi-conformal distortion 80th percentile
qcd_perc90	Quasi-conformal distortion 90th percentile
qcd_perc99	Quasi-conformal distortion 99th percentile
qcd_min	Minimum Quasi-conformal distortion
qcd_max	Maximum Quasi-conformal distortion
qcd_avg	Average Quasi-conformal distortion (weighted by 3D area)
qcd_stddev	Quasi-conformal distortion standard deviation
qcd_discardedArea	3D area of outlier elements that were discarded when computing qcd statistics
sf_perc1	UV-scaling 1st percentile
sf_perc10	UV-scaling 10th percentile
sf_perc20	UV-scaling 20th percentile
sf_perc30	UV-scaling 30th percentile
sf_perc40	UV-scaling 40th percentile
sf_perc50	UV-scaling 50th percentile
sf_perc60	UV-scaling 60th percentile
sf_perc70	UV-scaling 70th percentile
sf_perc80	UV-scaling 80th percentile
sf_perc90	UV-scaling 90th percentile
sf_perc99	UV-scaling 99th percentile
sf_min	Minimum UV-scaling
sf_max	Maximum UV-scaling
sf_avg	Average UV-scaling (weighted by 3D area)
sf_stddev	UV-scaling standard deviation
sf_discardedArea	3D area of outlier elements that were discarded when computing sf statistics

Raster statistics

For each texture image, TexMetro computes the following statistics at multiple MIP levels and groups them in a list sorted by increasing MIP level

Entry	Description
rw	Raster width at the current MIP level
rh	Raster height at the current MIP level
totalTexels	Number of mapped texels in the texture
totalTexels_bilinear	Number of texels involved in bilinear interpolations
overwrittenTexels	Number of texels that are mapped to at least two different triangles
lostTexels	Number of texels that are lost due to overwrites
texelClashes	Number of texels that can interfere in the bilinear interpolation of texels from different charts
boundaryTexels	Number of boundary texels