Interest in cross compiling to webassembly

[bwrsandman]

I'm very interested in using libigl for interactive simulations and posting them online. Supporting webassembly and webgl through emscripten could make any application linking against this library more accessible.

I've created a branch which can do this with minimal changes. A few #ifdef, extracting the main loop, disabling comiso and embree, disabling popen and disabling wireframe mode.

If there is interest in this, I can contribute my changes as a few PRs.

This is my branch: https://github.com/bwrsandman/libigl/tree/emscripten

Here is the webassembly interactive draw mesh tutorial: https://bwrsandman.github.io/libigl

[jdumas]

That is really cool. We've considered working on a emscripten version a while back (in fact I had a branch myself enabling this), but we never had time to polish it out. Now our new python bindings come with a WebGL viewer as well, so we don't have a strong incentive to work on an emscripten port.

That being said if the changes are minimal I'd be interested in seeing a PR with the list of changes. Not sure if we'd be able to merge them, but I can at least take a look. You'd need to base it off of the dev branch though, since master is now a bit old.

[bwrsandman]

I rebased to dev. It get compile errors in eigen which I didn't have before. Not sure if its already known.

libigl/include/igl/arap_rhs.h:38:12: error: no template named 'SparseCompressedBase' in namespace 'Eigen'
    Eigen::SparseCompressedBase<DerivedK>& K);
    ~~~~~~~^
libigl/include/igl/arap_dof.cpp:227:3: error: no matching function for call to 'arap_rhs'
  arap_rhs(V,F,V.cols(),data.energy,K);

Here are the changes from dev. https://github.com/libigl/libigl/compare/dev...bwrsandman:emscripten-dev

[BruegelN]

Hi @bwrsandman the version of Eigen used in masterand dev differs. Set the cmake variable LIBIGL_EIGEN_VERSION to 3.3.7 should do the trick.

[bwrsandman]

Thanks. That seems to have fixed it. Is there an option to not use SIMD as webassembly simd is a bit different from emmintrin.h?

[Philius]

I forked libigl and have an inline/header-only build in event-horizon-webassembly that builds to desktop and the web with a "dear imgui" menu and the bunny mesh.

set "USE_EMSCRIPTEN = 1" in the makefile for a web build, "USE_EMSCRIPTEN = 0" for a desktop build

It's loosely based on sketchpunk/FunWithWebGL2 I hit a wall getting barycentric wireframe creation - something to do with the number of columns = 4. The shader implementations expect a "w" vertex paramater as well as x,y,z to do it's thing, but I've no idea how to proceed. I hit an eigen assert that I don't understand.

set "USE_BARYCENTRIC = 1" in the makefile for a barycentric wireframe build, "USE_BARYCENTRIC = 0" otherwise

[Philius]

I got it working ! Now if somwone who understands uniforms in WebGL can step in to wire up the face and edge colours, no backface culling, probably more that I missed, your feedback is welcome!