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View Full Version : how to draw a geometry with higher teseellation



pango
08-23-2003, 09:31 PM
the geometry with higher tessellation looks more reasonable in some effects,but how to draw it?

AdrianD
08-24-2003, 05:32 AM
Originally posted by pango:
the geometry with higher tessellation looks more reasonable in some effects,but how to draw it?

how to render more polygons ? just throw more polygons at your gpu !!! http://www.opengl.org/discussion_boards/ubb/wink.gif
but seriously: i think you are lookng for tesselation and subdivision algorithms. just google for: "subdivision surfaces", "bezier","bezier patches" or "polygon tesselation".

matt_weird
08-24-2003, 10:41 PM
another thing is that chip vendors are providing specific technology/extensions for such kind of polygon tesselation. i don't know what nVidia did exactly, but ATI has their TRUFORM technology, which does the polygon tesselation assuming the polygon vertex normals and gives a subdivision of a particular polygon and represents a convex shape of it in a set of a smaller triangles, giving a smoother looking surface as a result. Minus of this one is that it is done in software(driver) http://www.opengl.org/discussion_boards/ubb/frown.gif , but i believe it is optimized in any way so that it can work better than any algorithm you will use http://www.opengl.org/discussion_boards/ubb/wink.gif Here you can find some info on TRUFORM technology and PN Triangles extension for it(ATI_pn_triangles):
http://www.ati.com/developer/truform_faq.html
http://www.ati.com/developer/sdk/RADEONSDK/Html/Info/ATIX_pn_triangles.txt

vember
08-25-2003, 12:58 AM
"ATI's TRUFORM™ implementation occurs completely in silicon."

says so in the doc.

matt_weird
08-25-2003, 06:16 AM
oops, sorry -- this what i've read that confused me a bit about it, heh:


Some games may actually allow TRUFORM™ to be rendered in a "software" mode on hardware which does not directly support TRUFORM™. While this will add visual appeal, it requires more of the system CPU cycles. This can significantly reduce a game's frame rate.
http://mirror.ati.com/support/infobase/3945.html

Anyway,


With a product that supports TRUFORM™ in hardware, such as the RADEON 8500, the graphics rendering occurs within the Graphics Processing Unit (GPU). The games visual appearance is greatly improved, while having a minimal affect on frame rates.

sorry for a confusion! http://www.opengl.org/discussion_boards/ubb/smile.gif

zeckensack
08-25-2003, 07:14 AM
ATI's marketing material is a bit misleading. There are exactly two graphics cards known to man that implement n-patch tesselation (aka TruForm) in hardware:
Radeon 8500 (/LE)
Radeon 9100

Everything else is software preprocessing. And slow.