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hemicube

OpenGL Strange GL_LINE_STRIP behaviour

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Ok, so I'm getting these really strange gaps in continuous line-strips. I've never seen this happen before and I've done my share of OpenGL/GFX programming. My graphics card is an ATI mobility x1400 running on Vista :S My actual application is drawing lots of fairly tessellated B-Splines, but right around where the tangent on the curve is close to pi/2 I get these annoying gaps!! I thought it might have something to do with my tessellation code but it's really impossible to get a gap with a single LINE_STRIP prim... Here are some pics of the problem and a small code clip that exhibits the same problem, just as a sanity check! :) Cropped version, 1:1 no scaling of any sort. Zoomed in quite a bit to get a clear view of that lovely gap and obvious lack of a pixel.
glBegin(GL_LINE_STRIP);
for (u32 i = 0; i < 32; i++)
{
	f32 t = (f32)i / (32.0f - 1.0f);
	f32 x = cosf(t*kPi)*4.0f;
	f32 y = sinf(t*kPi)*4.0f;

	glVertex2f(x, y);
}
glEnd();


I have a feeling this has something to do with Vista's mediocre OpenGL driver support, any insight on this would be awesome as I'm getting ready for another release and this is kinda holding me back... Chris __

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You can try updating your driver or just switch to a software rasterizer. At least with the soft rast, you and your users always get the same result.
For the soft rast, www.mesa3d.org and it's pretty fast.

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I am using the latest driver, and there is no way I'm going to be able to use a software rasterizer. I'm drawing on the order of 30k-40k line segments @ 60FPS so I need the acceleration.

I think it must be a driver issue as I'm having the same problem in D3D using similar code. I guess it's not something I should worry about too much as hopefully others won't have this problem.

It's just a little surprising that the Vista drivers are really this bad on a decent system.

Dell E1505 Core Duo @ 2Ghz, 2GB Ram and an ATI X1400...

Has anyone else even seen this sort of behavior in OGL via drivers?


Chris
__

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Well I just tried it in Linux and got the same results, I should add that you only see it when the object is translating out at certain points. Grrrr!

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