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Curved Surfaces?


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#1 Jankey   Members   -  Reputation: 122

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Posted 15 September 2001 - 01:05 AM

If everyone of you knows Quake 3 ... you know the the Engine has Curved Surfaces ... That means ... The Object is more smooth than it has Polygons ... how does this work?`... i think there musst be a way get more information about the 3D Calculations on the 3D Card and how to manipulate then? .... does anyone of you have a Code or a link? It would be interresting to do this by the Graphics Accelator on the Graphics Card ... if you have information please post ... thx J@nkey

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#2 Anonymous Poster_Anonymous Poster_*   Guests   -  Reputation:

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Posted 15 September 2001 - 02:34 AM

There''s a BezierPatch Nehe Tutorial.

#3 Anonymous Poster_Anonymous Poster_*   Guests   -  Reputation:

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Posted 15 September 2001 - 03:27 AM

i may be wrong, but i read somewhere that the curves are tesselated at load time, and treated as vanilla triangles from then on. so they go to the 3d card as tris...

#4 zedzeek   Members   -  Reputation: 528

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Posted 15 September 2001 - 09:57 AM

yes i handle curves the same way, the info for the curves is stored as control points but i first create a surface of triangles from these points before i give it to opengl. thus it gets treated no different than normal surfaces

#5 Anonymous Poster_Anonymous Poster_*   Guests   -  Reputation:

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Posted 15 September 2001 - 10:01 AM

also, if you are interested in curved surfaces calculated in hardware, look under n-patches. The dx sdk docs have info on them, the nvidia developer site has info on them. The ati developer site has info on them.

#6 Anonymous Poster_Anonymous Poster_*   Guests   -  Reputation:

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Posted 15 September 2001 - 08:35 PM

watch out thoiugh thats only in harware with geforce3 + radeons

#7 Jankey   Members   -  Reputation: 122

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Posted 16 September 2001 - 03:28 AM

hmm i think for this i need more information of the Handling of OpenGL 2 the Graphics Acelerator ... do you know a link?

#8 Jesper T   Members   -  Reputation: 322

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Posted 16 September 2001 - 08:04 AM

Howdy, i''ve been workin a little with curved sufaces, take a look at these screens here:

http://home.online.no/~7396/delta/

All of those are based on 12 control points (cept the cylinder thingy)

Basically what i did was to make a X*X grid based on four bezier patches

I also found out that to calculate the suface itself takes some time if the grid gets much more detailed than 20*20 quads (still a lot less than a sec though, but noticable)
So i recon that the curved surfaces in quake is pre-calculated, and then how many polys it use probably depends on framerate or maybe distance from the camera (I dont know for sure, but it seems more logical to me)

The way I did this may not be the best way though, I never read any tutorials on it, just got the formula for bezier curves from a web site and found the rest out myself. But if u got any questions of how to use the bezier thingy, just ask.

JT

#9 Vlion   Members   -  Reputation: 151

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Posted 17 September 2001 - 12:34 PM

Computer Graphics: Principles and Practice.
Look up that book. Its got a section on curves in 3D.
~V''lion

I came, I saw, I got programmers block.
~V''''lion

#10 Jankey   Members   -  Reputation: 122

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Posted 17 September 2001 - 10:17 PM

hmm quite Interresting ... But i want to use more of the Graphics Accelerator Speed of my GeForce 2, I know John Carmack used his own rouines to get this with the Surface ... ( I Thing it would look nice with specular Shading *gg* )




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