UV Projection Mapping and Gladius

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I am making my way slowly into the world of 3d gaming, focusing exclusively on Gladius so far. It can be a bit overwhelming looking through code. In a previous life, I could fake my way through Hamiltonian physics, but I may have a breakdown if I need to figure out quarternions. Up tonight, I hope to get a better grasp on something a little easier: some of the options in "meshes" and how they relate, if at all, to Gladius CubicVR.

The Cubic VR JavaScript project bills itself as a WebGL-based 3d engine. Gladius is also an engine, but a game engine, not a 3d engine. Probably in an effort to cut down on confusion, Gladius calls Cubic VR a rendering backend, not another "engine". Similarly, the Gladius Box2D extension is a physics backend, not an engine. So Gladius is a game engine that is comprised of a number of backends that typically think of themselves as engines of one sort or another. I think that makes sense in a weird way.

Anyhow, the mesh in the cube example has two entries that I don't quite understand:

  var mesh =
  {
    // ...
    uv: [
      [ [0, 1], [1, 1], [1, 0], [0, 0] ],
      [ [0, 1], [1, 1], [1, 0], [0, 0] ],
      [ [0, 1], [1, 1], [1, 0], [0, 0] ],
      [ [0, 1], [1, 1], [1, 0], [0, 0] ],
      [ [0, 1], [1, 1], [1, 0], [0, 0] ],
      [ [0, 1], [1, 1], [1, 0], [0, 0] ]
    ],
    uvmapper: {
            projectionMode: "cubic",
            scale: [1, 1, 1]
    }
  };

I am none too sure what "uv" represents, but there are six sides to a cube and there are six entries in the uv property. A quick bit of research (in other words, I looked it up on Wikipedia), turns up that UV mapping is the mapping done onto a projected space. So, on each of the faces of a cubic (with cubic projection), u and v are what x and y would be in normal 2d Cartesian space. At least that's what I think it is.

I am not sure what mucking with UV order would do. I rotate the first face's UV mapping:

  var mesh =
  {
    // ...
    uv: [
      [ [1, 0], [0, 0], [0, 1], [1, 1] ],
      [ [0, 1], [1, 1], [1, 0], [0, 0] ],
      [ [0, 1], [1, 1], [1, 0], [0, 0] ],
      [ [0, 1], [1, 1], [1, 0], [0, 0] ],
      [ [0, 1], [1, 1], [1, 0], [0, 0] ],
      [ [0, 1], [1, 1], [1, 0], [0, 0] ]
    ],
    // ...
  };

But that has no effect that I can discern:



Looking through the CubicVR documentation on Mesh it seems like I can set a color for each face point, but I cannot figure out why I would want to do that.

It seems, at least superficially, like there is more interesting stuff to be done in the material settings. Per the CubicVR.js documentation on Material, I ought to be able to add an image on each projection. So I grab an image from the CubicVR.js project:

wget https://github.com/cjcliffe/CubicVR.js/raw/master/samples/images/1422-diffuse.jpg

And add it to the material definition for my cubes:

        return {
          textures: {
            color: '/images/1422-diffuse.jpg'
          },
          opacity: 0.9
        };

With that, I get cool textured cubes spinning about:



I think this UV projection stuff is starting to make some sense. To be sure, I will probably continue with this tomorrow, possibly experimenting with other shapes.


Day #407