Description

Application

Problems

Approach

VRML, the Virtual Reality Modeling Language, is a standard format for 3-D objects and scenes. Complex 3-D objects easily overload even hardware- assisted rendering and compromise interactive frame rates needed for VR applications. To overcome this restriction, objects (usually defined as a polygonal representation) are stored in multiple levels of detail with progressively decreasing polygon counts. At runtime, an appropriate level of detail is selected to obtain the maximum image quality, and avoid overload of the rendering pipeline.

However, manual creation of levels of detail for complex models is too labor intensive. Therefore, a tool is needed to generate LODs (levels of detail) automatically.

We have implemented such a tool that supports VRML. It is able to reduce indexed face sets (polygonal data) and indexed line sets that embody the bulk of VRML data commonly found in VRML models. The algorithm is based on octree quantization of vertices (originally developed for color reduction by Prof. Michael Gervautz already in 1987).

The tool reads a VRML file and generates LODs for each IndexedFaceSet and IndexedLineSet. Further the tool removes double defined coordinates, materials, normals, texture coordinates, faces and lines within the VRML nodes. The resulting VRML scene will be written into a new file.

Publications