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Copyright Alec Jacobson 2015

Cocoa and GLUT applications wrapping the Skinning class for prototyping linear blend skinning and other real time deformations methods. This also functions as the demo code for the SIGGRAPH paper "Fast Automatic Skinning Transformations" by Jacobson et al. 2013. To jump to the relevant code for that paper, see igl/arap_dof.h in libigl

Note about name

The previous name of the project files was "skinning". Since this program is really a prototype program for "Fast Automatic Skinning Transformations", this old name was a bit too general. Nevertheless some of the files and projects keep this name as a legacy to avoid the ugly refactoring required when renaming.


  • git submodule:
    • libigl (IGL's header library)
      • Eigen3 (matrix library)
      • AntTweakBar (OpenGL GUI toolkit)
  • OpenGL (realtime rendering)
  • Cocoa (UI on Mac OS X)
  • GLUT (extra openGL utilities: displaying text, UI on everything else)
  • Optional dependencies
    • tetgen (tetrahedral meshing)
    • mosek (quadratic programming optimization)

Compilation notes

Eigen's Block.h was giving some warnings, so I've temporarily turned of warnings for implicitly converting 64-bit types to 32-bit types: GCC_WARN_64_TO_32_BIT_CONVERSION



libigl is included as a git submodule, so it's frozen to a commit that is known to be compatible with this application. Libigl contains in libigl/external, the AntTweakBar, tetgen, and eigen depedencies. Libigl and eigen are header only, thus you will only need to build libraries for AntTweakBar and Tetgen.


AntTweakBar is an OpenGL/DirectX library for simple UI. Use the version in libigl/external/AntTweakBar. There are a variety of Makefile.*s in libigl/external/AntTweakBar/src. Use Makefile.osx.igl if you're on Mac OS X. E.g.,

make -C libigl/external/AntTweakBar/src -f Makefile.osx.igl


Tetgen is used to tetrahedralize 3D solids given a surface mesh. This is optional in the sense that you should be able to disable any use of it without disrupting the "FAST" portion of the code. Tetgen is easy to compile:

make -C libigl/external/tetgen tetlib

Compilation and Execution

Linux/Unix command line

cd skinning/
./skinning ogre/

Mac OS X

open skinning.xcodeproj

You'll probably have to adjust the header search paths and library locations. Then you should be able to:

Build and Run


Completely possible. Not supported. Try your luck with the VS project.


To run the command line program issue

./skinning ogre/

This will open the ogre example.

Press 't' to toggle displaying the filled triangles of the mesh.

Press 'l' to toggle displaying the wireframe of the mesh.

The "state" of this program is partly determined by which shader is being used. To toggle between shaders, use the '<' and '>' keys.

Switch to the LBS shader.

Press 's' to toggle displaying the skeleton

Click on individual bones or endpoints to select them.

Press 'r' to reset all bones to their rest positions.

Press 'R' to reset selected bones.

Right-click and drag on an endpoint to rotate the bone about its parent

Right-click and drag on a bone to wist about its axis

Left-click and drag on a bone or endpoint to translate (not so useful, yet)

The "Fast Automatic Skinning Transformations" method may be activated by setting appropriate parameters in the "AutoDOF" group of the GUI and toggling "Auto DOF" by pressing 'D'.

Press 'D' to turn on "Auto DOF" and wait for precomputation to complete.

Left-click and drag on Yellow endpoints to set position constraints.

Select an endpoint and hit 'f' to toggle its type:

Color Constraint type
Red fully constrained
Pink linearly constrained (position is free)
Yellow positionally constrained (linear part is free)
Green completely free

Right-click and drag red endpoints to apply full rigid transformations

Help for the GUI is available by clicking the little question mark in the bottom left corner.


Zip this direcotry without .hg litter using:

make -C skinning clean
rm -rf build
zip -9 -r --exclude=@exclude.lst ../skinning

Bundling dependencies

Download Alec's patched version of dylibbundler and run the following:

dylibbundler -od -b -x ./ -d ./
install_name_tool -change @loader_path/libmosek64.7.0.dylib @executable_path/../libs/libmosek64.7.0.dylib  ./


Please use the issues page or contact Alec Jacobson if you have questions or comments.


Fast Automatic Skinning Transformations







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