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Julien Cayzac
06-23-2002, 05:51 AM
I've never used evaluators, so I was wondering: are they slow ? I mean, is it possible to write a game engine using exclusively Bezier patches, or is it still SF ?

Thanks,
Julien.

Bob
06-23-2002, 06:47 AM
And what is "fast" for you?

If they are fast enough for you, then yes, you can use them in your game engine. And what's fast enough and what isn't is up to you to decide. Why not try them, and see if they are fast or not?

Whether they are software or hardware accelerated is irrelevant. Would you skip them just because they are software, even if they are fast? Software is not the same as slow.

Julien Cayzac
06-23-2002, 07:33 AM
Originally posted by Bob:
And what is "fast" for you?
I answered to that in my original post. Fast = suitable for a game engine which exclusively use them. ie, 0 triangle-based models, and 1000s patches. Fast also means >60fps, of course http://www.opengl.org/discussion_boards/ubb/smile.gif


Why not try them, and see if they are fast or not?
Why not trying marching cubes and implicit surfaces ? http://www.opengl.org/discussion_boards/ubb/smile.gif
I don't want to waste my time working on something everybody (but me) knows to be slow. What's why I ask...

To make the scope of my question clearer: are they fast when HW accelerated (on NV20) ?

Julien.

jwatte
06-23-2002, 09:48 AM
Everyone else may be using it differently from you.

It's not THAT hard to code up a cheap GLUT app which throws 1000 randomly generated textured patches on the screen. Then run this app on 3 different cards (GF2, Radeon and Intel Built-in Graphics Decellerator, say) to get your own opinion. This should be two days, tops.

Compare two days to the ten man-years of creating an actual shippable game engine and it's very cheap and worthwhile research to do up-front. Who knows, perhaps you even learn something new by doing it!

knackered
06-23-2002, 12:43 PM
Higher Order Surfaces
19. What types of higher order surfaces are supported by GeForce3?
B-Splines, Bezier patches, and Catmull-Rom splines are all supported in hardware.

20. Are these tessellated by the driver or by the hardware?
GeForce3 has hardware support for curved surface tessellation. It is not done in the driver.

21. Is it possible to modify control points using vertex shaders?
No. Surfaces are tessellated before getting to the vertex shader, so control points are not available at that point in the pipeline. However, you can use vertex shaders to operate on the vertices generated by the hardware tessellator.

I think this is new to the geforce range - so it starts at geforce3 in hardware.

(this is from: http://developer.nvidia.com/view.asp?IO=geforce3_faq )