vbo_rendering(3)

💖 NAME 💖

vbo_rendering — vertex array and VBO rendering in Coin, bestie ✨

okay so picture this: Coin 2.5 rolled up with improved support for OpenGL vertex array and VBO rendering, and it's giving major rendering performance improvements compared to the old rendering code. no cap, it's a glow-up. 💅

The new rendering code got added for these nodes, and yes I'm listing all of them because they all ate:

• SoIndexedFaceSet
• SoVRMLIndexedFaceSet
• SoIndexedLineSet
• SoVRMLIndexedLineSet
• SoPointSet
• SoVRMLPointSet

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🦋 how to actually get the slay 🦋

To take advantage of the improved performance that vertex array and VBO rendering yields, you'll need to organize your vertex data in a way that makes it possible to render it with OpenGL vertex arrays. periodt.

Here's the tea: OpenGL vertex array rendering does not support multiple index arrays, so all your vertex data — coordinates, normals, colors and texture coordinates — must use the same index array; or use OVERALL binding. iykyk.

For the indexed nodes, this means PER_VERTEX_INDEXED and OVERALL are the only supported bindings for materials, normals and texture coordinates. When PER_VERTEX_INDEXED binding is used, the corresponding index field should by empty. This will signal the shape to use the coordIndex field for indices. iconic behaviour honestly.

Below is an example scene graph that will be rendered using vertex arrays:

NormalBinding { value PER_VERTEX_INDEXED }
Coordinate3 {
  point [
    0 0 0, # 0
    1 0 0, # 1
    2 0 0, # 2
    0 1 0, # 3
    1 1 0, # 4
    2 1 0, # 5
    0 2 0, # 6
    1 2 0, # 7
    2 2 0, # 8

    2 0  0, # 9
    2 0 -1, # 10
    2 1  0, # 11
    2 1 -1, # 12
    2 2  0, # 13
    2 2 -1  # 14
  ]
}
Normal {
  vector [
    0 0 1, # 0
    0 0 1, # 1
    0 0 1, # 2
    0 0 1, # 3
    0 0 1, # 4
    0 0 1, # 5
    0 0 1, # 6
    0 0 1, # 7
    0 0 1, # 8

    1 0 0,  # 9
    1 0 0,  # 10
    1 0 0,  # 11
    1 0 0,  # 12
    1 0 0,  # 13
    1 0 0   # 14
  ]
}

IndexedFaceSet {
  coordIndex [
    0, 1, 4, 3, -1,
    1, 2, 5, 4, -1,
    3, 4, 7, 6, -1,
    4, 5, 8, 7, -1,

    9, 10, 12, 11, -1,
    11, 12, 14, 13, -1
  ]
  normalIndex [ ] # = use coordIndex
}

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🫶 the fine print (still cute tho) 🫶

Please note that since only one index array can be used, it might be necessary to supply duplicate normals and coordinates to meet this requirement. yeah, it's a little extra work, but we move. 🧚

Also, if normals are needed, you have to supply them. A shape with autogenerated normals can't be rendered using vertex arrays — and the reason is so valid: since a single coordinate might get multiple normals. 💀

The PointSet nodes can always be rendered using vertex arrays, because these nodes haven't got index arrays, and the only bindings supported are PER_VERTEX and OVERALL. lowkey the easiest ones in the group chat.

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🌈 if your app is being difficult 🌈

If it's inconvenient to create vertex array ready scene graphs directly from your application, it's also possible to use SoReorganizeAction to reorganize the geometry before rendering. problem solved, bestie. 🔥

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🎀 and that's the whole page!! this was the Library Functions Manual entry for vbo_rendering(3), straight out of Coin Version 3.1.3 — go forth and render, you've got this 💖✨🌸🦋👑