What's a polygon soup?

From my understanding, a polygon soup is a mesh that consists of a collection of triangles with no particular ordering. Optimized meshes contain triangle strips, fans, etc to make drawing faster.

Yeah, except it''s more about space partitioning than triangle strips and fans. A polygon soup is the sort of thing that you create in 3D studio - i.e. just a bunch of triangles with no relation to each other. You then usually want to put those triangles into some sort of structure so that collision detection, vislibility determination and so on are easy and fast to calculate (structures like BSPs, oct trees, etc)

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From my experiences polygon soup''s are VERY bad. It makes collision detection very diificult as the polygons aren''t grouped into a coherent mesh, they can be anywhere. And if you use backface culling, there are times when you might not even see them. I was thought never ever to use polygon soups and they usually occur when a modeler makes a mistake.

Polygon soups are not bad. The term is simply given to any kind of polygonal geometry that hasn''t been clustered in any way, ie. at the stage where the octtrees, BSPs, protals, etc. have not been calculated yet.

The geometry is just a huge list of triangles at that point, with no relationship between them. If you export straight geometry out of a 3D modeling package (3DSMax, Maya, whatever) you will automatically get a polygon soup. As soon as you apply any kind of hierarchical sorting or clustering scheme, then it''s not called a polygon soup anymore.

/ Yann