[osg-users] Seeking advice: Efficient method for large grid rendering (terrain) with unique state per grid square

[John Peterson]

Thank you for your reply, Robert.

You mentioned PagedLOD nodes. While I might not use the paged version of the LODs nodes just yet, I've been thinking a lot about whether LOD nodes are the way to go in order to get OSG to cull large portions of my terrain without having to traverse and render every single grid square in the world. I'd be interested to know if the following technique might succeed for my use case, which I could later extend to PagedLOD nodes as I increase the area of my terrain.

For the purposes of this very simple example, imagine a 4x4 grid where each one of the 16 grid squares represents a 5000 m^2 area of terrain. I should have been clear in my original post and mentioned that the grid squares are literally that--four vertices to render a pair of triangles. (In other words, it's not a particular complicated terrain from a geometric standpoint.) I'm wondering if I could use LOD nodes hierarchically in order to partition the scene in such a way that OSG will simply discard entire quadrants that are too far away from the viewer. To illustrate more clearly the scene graph I envision (excuse the ASCII art):


Code:
root
  LOD
    LOD
      geometry for square at (0,0)
    LOD
      geometry for square at (1,0)
    LOD
      geometry for square at (0,1)
    LOD
      geometry for square at (1,1)
  LOD
    LOD
      geometry for square at (2,0)
    LOD
      geometry for square at (3,0)
    LOD
      geometry for square at (2,1)
    LOD
      geometry for square at (3,1)
  LOD
    LOD
      geometry for square at (0,2)
    LOD
      geometry for square at (1,2)
    LOD
      geometry for square at (0,3)
    LOD
      geometry for square at (1,3)
  LOD
    LOD
      geometry for square at (2,2)
    LOD
      geometry for square at (3,2)
    LOD
      geometry for square at (2,3)
    LOD
      geometry for square at (3,3)



Of course, I'd have to carefully choose the LOD min and max values to ensure that I'm neither discarding too much of the scene graph nor including more than I actually need.

My question is, is this technique reasonable and scalable? Are there any pitfalls that I need to watch for, or any red flags that it raises?

Best regards,
John

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http://forum.openscenegraph.org/viewtopic.php?p=65101#65101