Question on loading my own PCA model

[Xingyu-Lin]

Hi, thank you for your code, it has been very helpful to me. But when I try to load my own pca model, I wonder how is your triangleList arranged?

[patrikhuber]

Hi Xingyu, Thanks, I'm glad it's helpful!

The triangle_list is a list of triangles that make up the mesh of the model. A mesh consists of vertices - but you also need to know how they're arranged to make up the triangles. triangle_list is just an array with each entry having 3 int's, and these are the vertex indices of one triangle.

Let's say your model has 20 vertices - the first few entries of triangle_list could look like:

{0, 1, 2} // the first triangle consists of vertices 0, 1 and 2
{1, 5, 7} // second triangle consists of vertices 1, 5 and 7
{1, 2, 9} // etc...
...

I hope that answers your question!

[Xingyu-Lin]

Yes, that solve my confuse. One little question regardless of this project: how to get a triangle list when I have the point clouds? OpenCV seems to support only 2D delaunay algorithm.

[patrikhuber]

Cool. In principle, you only need the triangle_list when you call functions like draw_sample, that will return a Mesh. So parts of eos should run without it.

I don't have much experience with mesh triangulation, but it's a standard problem in computer graphics. There must be many libraries out there that you can just quickly use to generate a triangle list. Even Blender can most likely do it, and that might actually be the quickest way!

[Xingyu-Lin]

Yeah, I solved that one through matlab interfere. Now I have another problem:( It seems that when you generate the mesh, you have considered the situation when there is no texture coordinate(I don't know what that is, maybe something for visualise in .obj file?), MorphableModel.hpp,line 173. But when you try to extract texture, you miss the case and in render_affine.pp line 76, in the reference to mesh.texcorrds[i], it will go wrong. Is there an easy way to fix this?

Really curious about what does the texture coordinates do in the morphable model

[patrikhuber]

I see your problem. First of all, think about what you are trying to do: You are trying to extract the texture (i.e. map the image-texture onto the mesh), and for that, I'm sure you understand that your model needs to have texture coordinates. If you're not familiar with texture (or UV) coordinates, it's the standard approach in graphics/games to texture a mesh. Have a quick read through that: UV mapping

So the fix is the following: Do you need/want to extract the original texture?

• If yes, your model needs texture-coordinates, for obvious reasons. I think Blender might be able to generate them too. For our model, we used a so-called "isomap projection" to get them.
• If no, then, just don't use extract_texture(...)?

Let me know if that helps, and if not, I'm sure we can work out a solution :-)

[Xingyu-Lin]

I took a few days on this issue and it seems like once I fit the image into my 3DMM, the texture on the image can be put into correspondence with the vertices naturally. The isomap does not seem necessary?

[patrikhuber]

Yes, after the fitting, you got this correspondence. But the isomap is for storing the texture. How would you store this information instead?

[patrikhuber]

Going to close this as the initial problem seems resolved. Feel free to re-open or create a new issue if you have other issues.