Efficient encodings for triangle meshes have recently become subject of great interest. The need for compact representations is fueled by the increasing popularity of 3D content on the Internet, where transmission bandwidth is a scarce resource.

In general compression schemes encode the topology seperately from the geometry of a triangle mesh. During geometry (de-)compression adjacency information can be exploited when using prediction and error correction schemes to encode the vertex positions.

Our work focuses on encoding the topology. I briefly speak about Mesh Collapse Compression, a vertex-based encoding scheme, which originated here at ICSI during my summer 98 stay and which was presented at SIBGRAPI 99.

Then I will present Triangle Fixer, a novel edge-based encoding scheme. Its main advantage over other schemes are its 'natural' extensions:

- Triangle Strip Compression
Decomposing a triangle mesh into triangle strips is desireable for fast rendering. "Good" stripifications reduce the number of vertices to be sent through the graphics pipeline by a factor of 2 ~ 3. Finding an optimal stripification seems to be in NP. All current mesh compression schemes loose the stripification, which needs to be recomputed each time after decoding the mesh. We present a scheme that stores both, topology and stripification in a very efficient manner.

- Face Fixer
The majority of meshes is not purely triangular. There are polygon meshes containing quadrilaterals, pentagons, hexagons, etc ... All current mesh compression schemes triangulate such meshes prior to compression. The original connectivity information is lost. This has disadvantages as it increases the number of faces and corners of the mesh. Those often have properties associated (normals, texture, colour) which then need to be specified multiple times. We show how to include such properties into the compression scheme. Furthermore a structure that groups faces of the mesh into logical units can be easily incorporated into the scheme. We consider the contributions of Face Fixer to be very significant and will submit it to SIGGRAPH 2000.