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Geforce 4 Transformations

Started by AndrewSmart May 28, 2002 at 8:54 AM 1 replies 200+ views

Original Post

May 28, 2002 at 8:54 AM

Hi all, I recently upgraded my Geforce 2 GTS to a blistering Geforce 4 Ti 4400. Trouble is the 3D application I''m developing is now exhibiting some strange artifacts.. The problem seems to be with the object transformations to world space. Each object in my world is tranformed to it''s world position by defining a pitch,yaw,roll angle and translation to the world position. This allows me to orientate it at any angle. With the Geforce 2 this all worked great. With the same app running on Geforce 4, any objects which have pitch applied, seem to render incorrectly. They appear in the wrong places, completely corrupted !! Does anyone have any clues as to why this may be, or can anyone point me in the direction of where to look for this nasty... Did something change in the transformation pipeline between Geforce 2 and 4 ? I know that G4 now supports pixel shaders etc, could it be to do with this not being configured correctly (i.e. is there something I need to set in order to tell it to act like a Geforce 2 ? ).... Yours puzzled, Andrew

DeltaVee

May 28, 2002 at 9:56 AM

I have had similar 'problems'.

For instance stuff that would render perfectly ok on an ATI AllInWonder Pro 128 would not on a Voodoo 5500 and vica versa.

Here is the problem, some drivers are more strict than others on what you give them to work with.

In other words, as with one of my problem, I had a buffer that was the wrong size, it was too small by 1 or 2 elements, it worked perfectly well on the ATI but rendered incorrectly on the Voodoo. No errors reported, go figure... Once I had fixed the buffer size problem, it would render correctly on both boxes.

In another case the scene would render on one box and not at all on another. In this case the failure was reported by the debug kernal and I could fix it quickly.

I then emailed the demo to a friend to test on thier NVidia grafix card and DX failed all together. ?????

The Moral : When developing software, periodically, run it on another machine that is configured differently. This will help catch bugs early on.

I know it is as annoying as hell, my very first completed game (DX 7) is a 3D asteroids, it is competely unplayable in anything other than my older Acer laptop (on which it was written). The scene rendering is totally screwed up and something is up with the Z-Buffering on my other two machines.

D.V.

Carpe Diem

[edited by - DeltaVee on May 28, 2002 11:00:37 AM]

AndrewSmart

Author

AndrewSmart

May 28, 2002 at 10:10 AM

Thanks for the reply..

There are certain upgrades you might expect problems with.. like from Voodoo''s to other cards, since Voodoo had a different texture pipeline setup which required textures to be loaded to the correct texture stage in the blending pipeline..

But when you upgrade a Geforce to a Geforce, I really didn''t expect any problems... Probably me just being naive... !!!

Looks like I''ll have to dig deep for this one..

Andrew

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