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Real-world examples of bezier patch meshes with vertex colors

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2020-04-12
2020-04-12
  • Michail Vidiassov

    Dear All,

    please, point me at examples of something like smoothelevation.asy
    from Asymptote gallery, mesh of Bezier patches with per-vertex colors,
    put to some real use, interactive use preferred.
    The reason: a convincing use case may help to push vertex colored
    NURBS into the next version of X3D standard, making it a better future
    output format for Asymptote (when, FSM willing, I'll have time to
    modify my 3D PDF output routines to produce X3D).
    I can find examples of meshes of Bezier, NURBS, or other curved
    triangles or quads and, easily, examples of flat triangle or rectangle
    meshes with vertex colors.
    But when I look for meshes with both non-flat elements and vertex
    colors I fail to find examples but among Asymptote examples.
    Sincerely, Michail

     
  • John Bowman

    John Bowman - 2020-04-12

    A good example, which I use in education is the complex Gamma Function:
    https://asymptote.sourceforge.io/gallery/3Dgraphs/gamma3.html
    If you press the m key you will see that the patches are not flat.

    A simpler example is the Bezier triangle in
    https://asymptote.sourceforge.io/gallery/3Dwebgl/vertexshading.html

    Here are two further examples from physics:
    https://asymptote.sourceforge.io/gallery/3Dwebgl/sphericalharmonic.html
    https://asymptote.sourceforge.io/gallery/3Dwebgl/p-orbital.html

    If you look at the PRC versions of these examples, you will see that they look "pixelated" (or worse, in the case of vertexshading) since each of the 4 vertices of a patch are forced to share the same color.

     
    • Michail Vidiassov

      Dear John (and All),
      I am looking for something out of Asymptote gallery.
      For example Asymptote output (bezier patches and verstex shaiding) used in a published work (not one about Asymptote).
      To convince people some feature is worth including in a public format I'd better show that there is demand for vertexcolored NURBS, not just that there is one tool that produces such obscure constructs.
      "Supply will create its own demand" is an argument, but demonstrating existing demand is better.

      Sincerely, Michail

       
  • John Bowman

    John Bowman - 2020-04-12

    It depends what you mean by published. Here is an online textbook that I co-authored:

    http://www.math.ualberta.ca/~bowman/m411/m411.pdf

    It will be difficult to find a 3D interactive non-tesselated example with vertex-dependent colors that wasn't drawn with Asymptote since none of the existing 3D graphics formats support this.
    That is precisely why we need v3d. :-)

     

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