different LOD approach?

General Discussion
1

Ive heard this somewhere and would like to know you opinion on it.
Basically with LODNode I need to have separate (not collapsed) nodes/geoms in the scene. But what about having 2 cameras: one to render the higher LOD scene and have a clip plane for the distance you want to switch LODs, then have the second camera render the lower LOD scene with Near/Far set to render after the first camera’s cliping plane? How would you do it?

2

What would the point of that be? You’d just make a simple and inexpensive process complicated. There’d also be visual artifacts in the middle.

Under a LODNode, only one (sometimes two on a FadeLODNode) level of detail is drawn at a certain time. There’s no need to worry about using up too many geoms.

3

Well, you need to have separate nodes for your objects in the scene for it to look right. This way you can have some of them flattened.

4

What’s the problem with having separate nodes? If they are under a SwitchNode, like a LODNode, then only one of them will be rendered anyway.

5

I dont mean that. I mean the number of separate nodes in the scene, not their lod levels.

6

Yes, it’s true that if you use LODNode, then your scene will have to have at least one Geom per LODNode. This is also true of almost any other thing that can make changes to the scene: if it is all one Geom, then it is a big, static thing that cannot be subdivided or changed. Changes are usually made by operating on individual Geoms, not operating within a single Geom.

But I don’t understand how playing games with two different cameras is going to make that any better.

If you want to reduce the number of Geoms used with an LODNode, what people usually do is replace a large group of LODNodes with its own low detail model, and parent that whole thing under an LODNode as well. Then when you’re sufficiently far away from the cluster, it becomes only a single node. It looks like this in the scene graph:

    LODNode
       |
  +----+---------------+
  |                    |
simple                root
model                  |
             +------------------+
             |                  |
           LODNode           LODNode
             |                  |
        +----+-----+       +----+-----+
        |          |       |          |
       low        high    low        high