Meshlab shading, lighting and color u3d file

Question

I am trying to create an animated 3D graph in pdf from a R 3D graph. I already saw different ways to do that (Asymptote, Meshlab, …). I want to use U3D file. So, I use rgl library to create the PLY file, and Meshlab to export my PLY file into an U3D file. File that I can export in pdf using LaTeX and Movie15/Media9 packages.

I managed to have animated 3D pdf without too much problems, but I lost colors on the way. I solve this problem, nonetheless, when I read the pdf “with colors” (vertex color or face color), I cannot have shading and lighting (whereas without colors, I have them).

Any idea how preserving shade/light and colors in the U3D file? I think it’s a problem with the U3D export or the U3D to pdf or the U3D format (?), because my PLY file opens correctly in Meshlab.

Thanks,

Answer 1

Here is what I did several years ago, starting with surfaces generated in Mathematica. I haven't used DAZ Studio or JReality lately, but this might still work.

First, the surface must be plotted with colors. Although the ContourPlot3D may appear in color on the screen in Mathematica, these colors come from the default lighting. The colors are not on the surface itself. We can draw the ContourPlot3D with colors using the following code:

superSphereColor = ContourPlot3D[x^4 + y^4 + z^4 == 1,
{x, -1, 1}, {y, -1, 1}, {z, -1, 1}, Mesh->False,
ColorFunction -> Function[{x, y, z}, Hue[z]] ]
Export["C:\\junk\\supersphereColor.obj", superSphereColor]

The Mesh->False option is highly recommended when creating plots, especially in color. Without this option, the resulting pdf file can be quite large, and can take a long time to open.

In this surface, the color, Hue[z], varies with z.

Then, export the plot as a (Wavefront) .obj file. When Mathematica exports an .obj file, it also creates an .mtl (material library) file, which contains the color information for the surface. We must then convert the .obj (and .mtl) files to a color .u3d file.

MeshLab sometimes cannot create a correct .u3d file with color information, so we must use other software to create a color .u3d file. Some non-free commercial software can do this.

DAZ Studio 4 (http://www.daz3d.com) is free software that can convert the pair of obj/mtl files into a .u3d file with color information.

JReality can also export color .u3d files, but the resulting color .u3d and .pdf files will be larger than the ones produced by DAZ Studio 4.

If a default picture comes up when you start DAZ Studio 4, use the menu option "Edit/Delete" to delete it. Use the menu option "File/Import" to import the .obj file. When importing, make sure the "Read Material Library (.mtl)" box is checked so the color information will also be imported.

You may also need to set the "Scale" to 100 so the image in the PDF file will not be too large, although this will depend on your original surface. As soon as you have imported the file, export it. Use the "File/Export" menu option to export the image to a .u3d file.

Finally, use the above LaTeX code to embed the .u3d into the pdf file. Different scaling may be required, so you may have to adjust some of the above numbers 3Daac ... 3Dcoo.

For color objects, we should use 3Dlights=CAD, not 3Dlights=Primary. The "CAD" option displays the object's own colors, and does not add artificial colors to it.

Notes: DAZ Studio 4 can also produce a monochrome .u3d file, although the resulting PDF file will be larger than if the .u3d file was created with MeshLab.