QC_tool: C++ library for visualization and processing of 2D and 3D meshes

This is a lightweight C++ library for visualization and processing of surface meshes and volumetric models. This library supports triangle meshes, tetrahedral meshes and voxel shapes. It is based on OpenMesh dataset and glut toolkit.

Technical report Video

Dependencies

• OpenMesh (mesh data structure)
• GMM (default linear solver)
• glut (OpenGL interface)
• glui (GUI interface for glut)
• ofxOctree (collision detection)

Binary

Windows executable: ./binary/qc_tool.exe

• It can be run in GUI or command line modes

• Additional windows libraries can be downloaded from qc_tool_libs.zip

Data formats

See ./data/ for examples of different input mesh formats

2D input

It supports .obj and .off files

3D input

Tetrahedral meshes and voxel shapes can be generated from closed surface meshes (obj , off)

Tetrahedral meshes with vertex attributes can also be loaded from .t files:

# tet mesh in .t format with a single vertex attribute
Vertex 0 -0.5  0.5 -0.5  0.0
Vertex 1 -0.5  0.5  0.5  1.0
Vertex 2  0.5  0.6 -0.4  2.0
Vertex 3  0.5 -0.6  0.4 -1.0
Tet 0 1 0 2 3

• Use scripts from ./utils/ to convert other 3D mesh files to .t format

Windows

windows	explanation
3D output	OpenGL/ GLUT main window
console output / input	info and additional inputs
GUI	Navigation and visualization of voxels and tetrahedra; lighting and mapping parameters

User manual

See animated examples in ./manual/

Data load & save

Key	explanation
'o'	load a mesh file (.obj, .off, .t)
Left CNTR + 'o'	Add tetrahedral mesh from .t file to previously loaded surface mesh
Left CNTR + 's'	Save surface mesh as .off or .obj file, and volume mesh as .t file

Camera

Key	explanation
Arrows up, down	Camera zoom in/out
Arrows right	Rotation animation
Mouse Left Button	Rotate around the origin

Voxelization

Open GUI from popup menu: Mouse Middle Button: Voxel > Voxel Properties

• This GUI divides volume contained inside a closed surface into voxels

item	possible values	explanation	image
Voxel form and number of divisions	Boolean and integers	Rectangular or cubic shapes of voxels. Cubic division and rectangular division specify how much voxels are generated along the x, y and z axes of the bounding cube and of the bounding box, respectively. See ./manual/generate_voxels.gif
Subdivisions	integers	First, bounding box is divided into specified number of cubic or rectangular voxels. Then, voxels contained inside the closed surface are recursively subdivided into a given number of sub-voxels. depth sets the maximal number of these recursive subdivisions
Cross section	X,Y,Z = doubles; sign ={-1,0,1}	It defines a cross-section of the volume for voxelization. If all parameters sign are set to zero (default), then the entire volume, contained inside the closed surface will be divided into voxels. Otherwise, each non-zero value of sign specifies a half space above (sign=1) or below (sign=-1) the planes x=X, y=Y and z=Z. The intersection of these half spaces is divided into voxels. See ./manual/cross_section.gif
Complementary cross	Boolean	Switch between the two modes: voxelize a cross-section of the volume, voxelize the complement of the cross-section

Visualization

• Standard shading modes are selected from the primary popup menu Mouse Right Button

  • Different geometry processing parameters can be visualized by selecting these parameters from the primary menu

    item	explanation
    Wireframe, Hidden lines, Solid smooth, Solid Flat	Standard shading modes
    Mean / Gaussian /Max normal curvatures, Cylindrical / Spherical coordinates and etc.	Visualization of different geometry processing parameters
    vAttribute	Color coded vertex attributes from .t mesh file

• Additional modes can be selected from the secondary popup menu Mouse Middle Button

  item	explanation	image
  Glue	Combine several visual modes. E.g., set the smooth shading with vertex normals and wireframe by clicking first Mouse Right Button: Solid Smooth , then selecting Mouse Middle Button: Glue > Glue vertex normal and Glue > Glue wireframe
  Color property	Material colors for surfaces, volumes and wireframes; directional and point source lighting (Color properties > Lighting )
  Set transparency	To enable transparent materials click MMB, select this menu item and then press '+' , '-' to adjust values of the alpha channel

• Open Voxel Navigate GUI to show cross-sections of volumes and to visualize selected mesh elements: Mouse Middle Button: Voxel > Voxel Navigate

  item	explanation	image
  Set axis for selections and cross sections	Drag and drop X,Y,Z arrow buttons. Set show coordinates to show the axes
  Cross section	In live cross section mode, drag and drop X,Y,Z arrow buttons. Otherwise press the Cross section button. Positive directions of cross planes are set according to sign elements from the Voxel Property GUI
  Selection	For volumetric meshes, press Select button to highlight the nearest vertex and its neighboring cells. Press Select face to highlighted the nearest triangular faces. Press move to selected to move coordinate axis to given indices of a vertex or a face (set index=-1 to disable selection)
  J method	Compute deformation Jacobian on the selected face / vertex.

• Press 'S' to select Edge/Face/Connected Component mode. Then, press '<' and '>' for iterating over these elements and '-' and '+' for adding/ removing neighboring elements to the selections

• Iteration over mesh elements

  item	explanation
  Select mode	Press 'S' to select Edge / Face / Connected Component modes.
  Iteration and propagation	Press '<' and '>' for iterating over these elements and '-' and '+' for adding/ removing neighboring vertices to the selections

Deformations and Parametrization

Meshes can be parametrized and deformed by selecting an appropriate item from the secondary menu ( Mouse Middle Button)

• Some of these deformations can be computed in the command line mode

• Deformations are computed with respect to the origin. Press 'a' to draw the axis and see the origin of the model

  • To align model click Mouse Right Button: Place at origin

• Press Tab to switch between the original and deformed models

  deformation	explanation	image
  UV mapping of surfaces	Compute linear parametrization for each connected component of surface mesh. Press 'u' ,'h' and 'm' to compute uniform, cotangent weighted and mean-value harmonic maps to a disc, respectively. Press 'b' for uniform harmonic mapping onto a rectangle (edges of rectangle are boundary vertices with maximal angles). Click MRB: Textured mesh , MRB: UV domain to show mesh texture and its target domain. Press '<' and '>' to rescale texture coordinates. For non-connected meshes use MMB: Color property > Component colors to highlight connected components
  Mapping of volumes/surfaces onto a ball/sphere	Click MMB:Volume Parametrization > Stretch to ball to map volumetric/ surface mesh to a ball. To enter additional mapping parameters click MMB:Volume Parametrization > Stretch to ball custom and MMB:Volume Parametrization > Stretch to ball from point and then enter these parameters in the console window ( for details see the bibliography)
  Mapping of volumes volumes/surfaces onto a cylinder	Click MMB:Volume Parametrization > Stretch to cylinder and enter the power of the mapping into the console. Note that these mappings are computed with respect to the origin ( for details see the bibliography)
  Quasi-conformal mapping of surfaces and volumes	Click MMB:Volume Parametrization > Map by folding,Map by folding, Map radial and press '-' and '+' to control the amount of the distortion. Additional deformations are computed by selecting items from the popup menu MMB:Zorich and MMB:conter power.
  Affine transformations	Open GUI Mouse Middle Button > Affine transformation to set translation, scale and rotation components of the mapping. Affine transformations can be applied to the boundary surface and to the interior volume, or to both of them.
  Noisy deformations	Click MMB:Add noise and press '-' and '+' to control the noise amplitude

Command line

It maps the given input mesh (-o) to a ball/ sphere and save results in obj, off or t files (-s)

qc_tool.exe -o input_file.t -s out_file.t -move2center -map2ball

optional flags	explanation
-move2center	First, move the center of the mass to the origin and then compute the mapping
-get_dist	Compute distortions obtained by the mapping

Source code

The source code, demo scripts and project files will be available in a near future

Bibliography

If you use this toolkit, please consider citing:

@inproceedings{naitsat2015volumetric,
  title={Volumetric quasi-conformal mappings},
  author={Naitsat, Alexander and Saucan, Emil and Zeevi, Yehoshua Y},
  booktitle={Proceedings of the 10th International Conference on Computer Graphics Theory and Applications},
  pages={46--57},
  year={2015}
}

@inproceedings{naitsat2016geometric,
  title={Geometric Approach to Estimation of Volumetric Distortions.},
  author={Naitsat, Alexander and Saucan, Emil and Zeevi, Yehoshua Y},
  booktitle={VISIGRAPP (1: GRAPP)},
  pages={105--112},
  year={2016}
}

License

This project is licensed under Mozilla Public License, version 2.0 - see the LICENSE file for details