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lun123

triangle or polygon?

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How do you define a "face" in your scene or terrain? face = triangle (3 indices/face) or polygon (>=3 indices/face)? Which one is better (faster fit to render pipeline, faster collision detection, etc.)?

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Yup same here, always face=triangle.

Its the most hardware friendly (i.e. most hardware only supports triangles). Almost all systems which allow non triangular polygons convert them to triangles at some stage.

The constraints etc make lots of the maths simpler.

The biggest VERY useful constraint I can think of is that a 3D triangle will never be concave or "twisted", it always lies in a plane. Concave stuff causes lots of "issues" for many things. The core of most collision is often a "something to plane" check. Backface culling based on winding order relies on a plane or "outness" to work properly etc...

--
Simon O''Connor
Creative Asylum Ltd
www.creative-asylum.com

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Yes, that is what I think too.

I asked this question because I just studied the Quake3 .bsp file format from gametutorials.com. The file defined a face as a polygon, and the tutorial sample code call glDrawArrays using triangle fans for every single non-culled face in render time.

So, I wonder isn''t it better to store a face as a triangle, so that it''s possible to group many faces and render by one call - using triangle lists.

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