Creating multiple shape versions
To control detail, model the same shape several times:
- high detail for when the viewer is close up
- medium detail for when the viewer is nearish
- low detail for when the viewer is distant
Usually, two or three different versions is enough, but you can have as many as you want.
Controlling level of detail
Group the shape versions as levels in an LOD grouping node:
- LOD is short for Level of Detail
- List them from highest to lowest detail
Syntax: LOD
An LOD grouping node creates a group of shapes describing different levels (versions) of the same shape:
- center - the center of the shape
- range - a list of level switch ranges
- children - a list of shape levels
XML Encoding
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<LOD center='0.0 0.0 0.0' range='...'> <!-- children ... --> </LOD> |
Classic Encoding
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LOD { center 0.0 0.0 0.0 range [ ... ] children [ ... ] } |
Optimizing a shape
Suggested procedure to make different levels (versions):
- Make the high detail shape first
- Copy it to make a medium detail level
- Move the medium detail shape to a desired switch distance
- Delete parts that aren't dominant
- Repeat for a low detail level
Lower detail levels should use simpler geometry, fewer textures, and no text.
A sample LOD
XML Encoding
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<LOD center='0.0 0.0 0.0' range='7.0, 10.0'> <Inline url='"torch1.x3d"'/> <Inline url='"torch2.x3d"'/> <Inline url='"torch3.x3d"'/> </LOD> |
Classic Encoding
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LOD { center 0.0 0.0 0.0 range [ 7.0, 10.0 ] children [ Inline { url "torch1.x3dv" } Inline { url "torch2.x3dv" } Inline { url "torch3.x3dv" } ] } |
Summary
Increase performance by making multiple levels of shapes:
- High detail for close up viewing
- Lower detail for more distant viewing
Group the levels in an LOD node:
- Ordered from high detail to low detail
- Ranges to select switching distances