Text Rendering Using GLSL in ImGui Menu (#1549)

* This is the code that renders the letter a for each vertex on the mesh paired with  a libigl-example-project

* Code for rendering just the number 12 on the 12th vertex

* Rendering vertices via glsl works, with geometry shader

* Added dynamic font scaling so accomodate ortho and perspective projections.

* Got faceids rendering

* Code cleanup

* This allows user to add custom text at some location rendered with the text shaders

* Dedicated separate VBOs for face and vertid labels

* Added in extra label rendering

* Moved texture binding to its own function and other code cleanup

* More conflict resolution when fetching upstream changes

* Resolved the relative path to font atlas

* Change scope variable for font atlas macro

* Removed PNG texture loaded from disk, and encoded font atlas into byte array. Other minor changes for VBO iterators and removed uneeded dependencies from previous commits

* Encapsulated text VBOs into struct to remove code duplication, and fixed bug for both overlay and text shaders being used at same time.

* Remove whitespace

* Tentative for Windows build fix not initializing TextGL structs in header

* Removed uniform that only belongs for text labels

* Added init and free methods for label buffers initialization and passing some args by reference on label methods

* Compressed font atlas that is under 50kB reduced from 330kB with decompression function

* Converting type from string literal to char array

* Broke up string literal

* Cleanup font atlas.

* Linux compile fix.

* Remove deprecated text pipeline.

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

tutorial/106_ViewerMenu/main.cpp

@@ -99,5 +99,6 @@ int main(int argc, char *argv[])
 
   // Plot the mesh
   viewer.data().set_mesh(V, F);
+  viewer.data().add_label(viewer.data().V.row(0) + viewer.data().V_normals.row(0).normalized()*0.005, "Hello World!");
   viewer.launch();
 }