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Matcaps (material captures aka environment maps) in Viewer#1482

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jdumas merged 4 commits intomasterfrom
matcap
May 2, 2020
Merged

Matcaps (material captures aka environment maps) in Viewer#1482
jdumas merged 4 commits intomasterfrom
matcap

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@alecjacobson alecjacobson commented Apr 13, 2020

Texture slot can be used as a material capture (also known as environment map). Swapping in a matcap from an image is very simple.

Here's a minimal example

#include <igl/opengl/glfw/Viewer.h>
#include <igl/read_triangle_mesh.h>
#include <igl/png/readPNG.h>

int main(int argc, char *argv[])
{
  igl::opengl::glfw::Viewer v;
  Eigen::MatrixXd V;
  Eigen::MatrixXi F;
  igl::read_triangle_mesh(argv[1],V,F);
  Eigen::Matrix<unsigned char,Eigen::Dynamic,Eigen::Dynamic> R,G,B,A;
  igl::png::readPNG(argv[2],R,G,B,A);
  v.data().set_mesh(V,F);
  v.data().set_texture(R,G,B,A);
  v.data().use_matcap = true;
  v.data().show_lines = false;
  v.launch();
}

For example, then
./main beetle.off Chrome.png will produce

Screen Shot 2020-04-12 at 8 30 59 PM

Chrome.png.zip

Note: I've disabled the automatic call to grid_texture() in ViewerData. I wonder if this was really being used as is like this. I made the judgement call that putting a default matcap in the texture is more useful (and that leaving the V_uv empty is more correct).

related posts:

@jdumas jdumas added the viewer label Apr 13, 2020
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This is cool! But I'm wondering if there's a use-case for showing a textured material with a matcap (e.g. to show a shiny heat equation solution or smth). If so, we should use different texture slots maybe?

include/igl/opengl/ViewerData.cpp Outdated
grid_texture();
// Alec: is anyone really using this default? It uses trivial UVs and
// produces an anisotropic checkerboard...
//grid_texture();
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Hmm I think this may be confusing to new users. If I enable textures I'd expect to see a (crappy) checkerboard more than a matcap I think?

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I can't imagine a circumstance where I want to see nonsense UVs + checkboard by default. Maybe we can trigger checkerboard texture generation if set_UV is called and use_matcap is (still) false?

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As said in my latest answer, I think we can kill the grid_texture() function, and as default behavior maybe do nothing? That way = no surprise.

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alecjacobson commented Apr 13, 2020 via email

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jdumas commented Apr 13, 2020

Sounds good. I'd still vote for keeping the grid_texture() by default though, otherwise lgtm.

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alecjacobson commented Apr 13, 2020 via email

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jdumas commented Apr 13, 2020

Oh right, I had in mind the grid from tutorial 501. It doesn't look like grid_texture() is very useful at all, maybe we should remove the method altogether? In that case I think the default behavior should be to not generate any UV/texture at all. Calling normal_matcap() by default would change the behavior of tutorial 501, and show the normal texture instead of the default checkerboard, which I think is a bit weird (if I load a mesh with a UV texture I'd rather see the checkerboard atlas than the mesh normal).

Do you think this matcap tick is worth a new tutorial entry btw?

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I've updated the grid_texture() function to only generate a checkerboard texture, but without UVs. Removing it entirely breaks tutorial 501.

@jdumas jdumas merged commit 29b7579 into master May 2, 2020
@jdumas jdumas deleted the matcap branch May 2, 2020 20:04
@jdumas jdumas added the feature label May 2, 2020
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jdumas commented May 2, 2020

Do you think it's worth a tutorial entry btw?

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alecjacobson commented May 2, 2020 via email

skoch9 pushed a commit to skoch9/libigl that referenced this pull request Jun 3, 2020
@alecjacobson @jdumas @skoch9
Matcaps (material captures aka environment maps) in Viewer (libigl#1482)
08dd106 
* matcap from texture, default normal image matcap

* update grid_texture() to generate checkerboard texture, but without UVs

Co-authored-by: Jérémie Dumas <jeremie.dumas@ens-lyon.org>
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