Multi-material example

[elalish]

Fixes #196
Fixes #286

This is a follow-on to #290 to demonstrate that the new property APIs work end-to-end by connecting them to glTF output. I've expanded MeshGL with a different style of MeshRelation data. I'm thinking I'll remove the old MeshRelation and triProperties input entirely now, basically saying Mesh is only for pure, simple geometry, while MeshGL is for anything requiring mesh properties and relationships.

[elalish]

Oops, I jumped the gun a bit; I still need to add the triangle reference into MeshGL so the tests can pass. Shouldn't be hard, hopefully I'll get to that tomorrow.

The next PR will be addressing #282 by adding a transforms vector that corresponds to the meshID vector. I think I'll even add some optional parameters to GetMeshGL() to specify which properties are normals so I can update them automatically.

[codecov-commenter]

Codecov Report

Base: 91.54% // Head: 91.36% // Decreases project coverage by -0.18% ⚠️

Coverage data is based on head (276f29f) compared to base (422c7f2).
Patch coverage: 87.75% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #309      +/-   ##
==========================================
- Coverage   91.54%   91.36%   -0.18%     
==========================================
  Files          33       33              
  Lines        3608     3626      +18     
==========================================
+ Hits         3303     3313      +10     
- Misses        305      313       +8     

Impacted Files	Coverage Δ
src/manifold/include/manifold.h	100.00% <ø> (ø)
src/manifold/src/impl.h	70.00% <ø> (ø)
src/manifold/src/shared.h	58.90% <ø> (ø)
src/utilities/include/public.h	73.49% <ø> (-0.32%)	⬇️
src/manifold/src/impl.cpp	94.42% <83.33%> (-1.26%)	⬇️
src/manifold/src/manifold.cpp	86.57% <90.32%> (-0.62%)	⬇️

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[elalish]

@geoffder FYI, I removed the MeshRelation API and removed them from your cbindings too, but you'll probably want to add in the other API changes.

[geoffder]

Is Mesh on it's way to be a purely internal class? I see that LevelSet still returns one, and there remains a Mesh constructor for Manifold, yet Smooth has been switched to take MeshGL.

[elalish]

I'm considering it. Definitely I'll update things like LevelSet to return one. The other constructor was superfluous since MeshGL already has a constructor that takes a Mesh, so really both are supported anyway.

[geoffder]

Huh, giving a Mesh to Smooth still compiles? Pardon my ignorance, but does C++ implicitly find the single argument constructor of MeshGL and just use that? Never would have expected that.

[elalish]

Yup, indeed it does. I think it's basically the same system that let's you pass 2 (an int) when the function wants a float.

[geoffder]

Interesting that it does the same on it's own for user defined types with no "class/inheritance relationship". Maybe just surprising to me due to my minimal C++ experience.

[geoffder]

@elalish Opened a PR with the new meshgl accessors: #311. Let me know if I've missed something!

[pca006132]

I won't be able to review this soon, I am currently on vacation for 7 days in Japan without my computer.

[elalish]

@pca006132 No problem, enjoy your vacation!

[elalish]

Good news: meshID is no longer needed as part of the public API - it is now internal-only. Likewise, no need for triProperties and such in the public API as we can use MeshGL for this input instead. I'm keeping the explicit Mesh constructors for now simply because they avoid some computation. I'd recommend that Mesh remain a C++-only construct though. For bindings to other libraries, better to directly create a Manifold and use MeshGL as the only I/O struct.