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marcus256
09-11-2003, 02:43 AM
Does ATI support their much hyped PN triangles extension? The ATI developer site says:


The RADEON™ does not support ATI_pn_triangles in hardware. The experimental extension (ATIX_pn_triangles) which exposed PN Triangles through software has been deprecated and is no longer available on RADEON.

What does this mean?

Has anyone ever used the ATI_pn_triangles extension?

kehziah
09-11-2003, 03:28 AM
It's available on R200 and up. Info you found on ATI's developer website is just garbage. The spec (http://oss.sgi.com/projects/ogl-sample/registry/ATI/pn_triangles.txt) at the registry was updated in late 2002. R200 accepts integer values for level of tesselation while R300 supports floats as well.

EDIT : well in fact it's not garbage. It's just old. It talks about R100, which does not support pn triangles in hardware, so the extension is not exposed (apparently it was exposed as experimental, and later removed).

[This message has been edited by kehziah (edited 09-11-2003).]

marcus256
09-11-2003, 03:35 AM
So, basically I can check for the support of "GL_ATI_pn_triangles", and then glEnable(GL_PN_TRIANGLES_ATI)? What about hardware performance and visual quality (real world examples, not ATIs happy papers)? Are there any apps using it today?

Ostsol
09-11-2003, 03:40 AM
The R3xx series does not fully support the feature in hardware. As such, those cards receive a relatively large performance hit for using the feature as compared to the R2xx line.

kehziah
09-11-2003, 03:56 AM
Here you can find a list of games with truform support : http://www.ati.com/products/gamesupport/index.html

One of the most popular is Half-Life / Counter-Strike. Works really well on human models. See the example on this page : http://www.hardware.fr/articles/388/page2.html

As far as performance goes, the hit is not that big on my 8500, provided that you don't use the max tesselation level (which increases triangle count insanely). Don't have practical experience with R300.

PanzerSchreck
09-11-2003, 07:13 AM
Ostsol is right.I own a Radeon9700 and i've written a md2/md3-viewer that supports PN-Triangles (you can get in on my HP, but it's written in Delphi).And since PN-Triangles are implemented in Software on the R3xx-Core, you'll encounter a bigger performance decrease especially when using higher tesselation levels.But for many cases, a low tesseltation is enough (as you can see in my viewer), so the hit won't be too big.

BTW : AFAIK the R3xx-Core supports TRUFORM2 (Don't know if it's called that), which gives you more freedom in terms of tesselation, but it also seems only to be supported under DirectX.

[This message has been edited by PanzerSchreck (edited 09-11-2003).]

[This message has been edited by PanzerSchreck (edited 09-11-2003).]