.TH "vbo_rendering" 3 "Thu May 29 2014" "Version 4.0.0a" "Coin" \" -*- nroff -*-
.ad l
.nh
.SH NAME
vbo_rendering \- Vertex array and VBO rendering in Coin 
Coin 2\&.5 added improved support for OpenGL vertex array and VBO rendering\&. This might lead to major rendering performance improvements compared to the old rendering code\&. The new rendering code has been added for the \fBSoIndexedFaceSet\fP, \fBSoVRMLIndexedFaceSet\fP, \fBSoIndexedLineSet\fP, \fBSoVRMLIndexedLineSet\fP, \fBSoPointSet\fP, \fBSoFaceSet\fP and \fBSoVRMLPointSet\fP nodes\&.
.PP
To take advantage of the improved performance 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\&. 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\&. For the indexed nodes, this means that 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\&. Below is an example scene graph that will be rendered using vertex arrays:
.PP
.PP
.nf
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
}
.fi
.PP
.PP
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\&.
.PP
Also, if normals are needed, you have to supply them\&. A shape with autogenerated normals can't be rendered using vertex arrays (since a single coordinate might get multiple normals)\&.
.PP
The PointSet nodes can always be rendered using vertex arrays since these nodes haven't got index arrays, and the only bindings supported are PER_VERTEX and OVERALL\&.
.PP
If it's inconvenient to create vertex array ready scene graphs directly from your application, it's also possible to use \fBSoReorganizeAction\fP to reorganize the geometry before rendering\&.