Problem creating a TCastleScene by code

Creating data (models, textures...)
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I’m playing with the example in Writing Code To Modify Scenes And Transformations. I 'm trying to create a scene from code using an old OpenGL 1.1 program I wrote time ago.

The problem is that I was using GL_TRIANGLES while Castle Engine seems to use GL_TRIANGLE_STRIP so when rendering the vertices seems in the correct places but the mesh is a mess (pun not intended) with all triangles overlapping. Am I right?

So is there a way to tell CGE to use GL_TRIANGLES?

Later I’ll dig in the sources and see if it’s possible to write my very own TCastleScene class. Maybe somebody can guide me in that travel…

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Replace TIndexedFaceSetNode (which is basically the equivalent of GL_QUADS) in the example with either TTriangleSetNode or TIndexedTriangleSetNode should work. Both use GL_TRIANGLES underneath.

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Thankyou kagamma. It works. :slight_smile:

I’ll look for more “SetNode” classes. I didn’t realize that it should be more.

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Adding to @kagamma answer:

  • While I also recommend to use TTriangleSetNode or TIndexedTriangleSetNode if you have only triangles, as it will be most straightforward…

  • …note that TIndexedFaceSetNode shown in Writing code to modify scenes and transformations | Manual | Castle Game Engine is also possible to use. TIndexedFaceSetNode renders a set of polygons, each polygon separated by -1 in the indexes. Polygons can be triangles, quads, or larger n-gons. They can be convex or concave (when TIndexedFaceSet.Convex = true, they must be convex; when it’s = false, they can be any kind). The example shows TIndexedFaceSetNode exactly because it allows to cover so many cases :slight_smile:

    I would not say that TIndexedFaceSetNode is like GL_QUADS or GL_TRIANGLE_STRIP (which were mentioned in this thread), and it actually never does use these primitive types.

    What it does:

    • Determine the polygons, looking at -1 separators in the indexes.
    • For each polygon, render it using a number of GL_TRIANGLES.
      • If Convex = true, each polygon is triangulated in a simple fast way, a bit like “triangles fan” (but not actually using GL_TRIANGLES_FAN, as it would prevent from having multiple fans in one draw call, unless one would do dirty tricks with degenerate polygons).
      • If Convex = false, each polygon is triangulated using ear clipping algorithm.

E.g. modify IndexedFaceSet.SetCoordIndex from Writing code to modify scenes and transformations | Manual | Castle Game Engine like this to have 3 triangles:

IndexedFaceSet.SetCoordIndex([
  0, 1, 2, -1,  // 1st triangle
  3, 4, 5, -1, // 2nd triangle
  6, 7, 8, -1, // 3rd triangle (note: ending -1 is allowed but  optional, doesn't really matter)
]);

See docs, in this case X3D spec for IndexedFaceSet node is helpful,

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