From: Craig M. <cr...@to...> - 2001-02-09 03:23:41
Attachments:
orbit_glut.c
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I searched the sourceforge bug database for this, but I found nothing. I will include as much info as I can so you can help me figure out if this really is a bug. So I am writing a very simple example from the OpenGL Programming Guide by Mason Woo and friends. It is the example of a sun (wire sphere) centered at the origin and a planet which can revolve and rotate. The basic program works. So I wanted to play with glFrustum, and thats when I noticed something strange. If I made the (x,y) coordinates of the bottom left or top right point of the near clipping plane (0.0, 0.0), I get some lines running from each sphere to the center of my viewport. However, if I use a really small number instead (or any non-zero number), the stupid lines do not show up. They say pictures are worth a thousand words, so I took screen shots for the following variations of my glFrustum call. /* This works correctly */ glFrustum(0.00001,0.5,0.00001,0.5,1.0,20.0); http://lothos.tool.net/planet_normal.jpg /* This does not */ glFrustum(0.0,0.5,0.0,0.5,1.0,20.0); http://lothos.tool.net/planet_bug.jpg I have also included the buggy version of my source code as an attachment should anyone wish to try it with their installation. I am running Mesa-3.4 on Debian Linux (potato/stable), X version 3.3.6 Later, \ Craig "Cowboy" McDaniel /_\ Software Engineer /_/_\ Internet Tool & Die /_/_/_\ cr...@to... /_/_/_/_\ (502) 584-8665 ext 108 |
From: Brian P. <br...@va...> - 2001-02-09 15:32:26
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Craig McDaniel wrote: > > I searched the sourceforge bug database for this, > but I found nothing. I will include as much info > as I can so you can help me figure out if this > really is a bug. > > So I am writing a very simple example from the > OpenGL Programming Guide by Mason Woo and friends. > It is the example of a sun (wire sphere) centered > at the origin and a planet which can revolve and > rotate. The basic program works. > > So I wanted to play with glFrustum, and thats when > I noticed something strange. If I made the (x,y) > coordinates of the bottom left or top right point > of the near clipping plane (0.0, 0.0), I get some > lines running from each sphere to the center of > my viewport. However, if I use a really small number > instead (or any non-zero number), the stupid lines > do not show up. > > They say pictures are worth a thousand words, so I > took screen shots for the following variations of > my glFrustum call. > > /* This works correctly */ > glFrustum(0.00001,0.5,0.00001,0.5,1.0,20.0); > http://lothos.tool.net/planet_normal.jpg > > /* This does not */ > glFrustum(0.0,0.5,0.0,0.5,1.0,20.0); > http://lothos.tool.net/planet_bug.jpg > > I have also included the buggy version of my source > code as an attachment should anyone wish to try it > with their installation. I am running Mesa-3.4 on > Debian Linux (potato/stable), X version 3.3.6 I've reproduced the problem here. It's a clipping bug. If you rotate the planets just right it also segfaults. I'm looking into this now and will try to have it fixed for Mesa 3.4.1 -Brian |
From: Brian P. <br...@va...> - 2001-02-09 16:53:05
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Craig McDaniel wrote: > > I searched the sourceforge bug database for this, > but I found nothing. I will include as much info > as I can so you can help me figure out if this > really is a bug. > > So I am writing a very simple example from the > OpenGL Programming Guide by Mason Woo and friends. > It is the example of a sun (wire sphere) centered > at the origin and a planet which can revolve and > rotate. The basic program works. > > So I wanted to play with glFrustum, and thats when > I noticed something strange. If I made the (x,y) > coordinates of the bottom left or top right point > of the near clipping plane (0.0, 0.0), I get some > lines running from each sphere to the center of > my viewport. However, if I use a really small number > instead (or any non-zero number), the stupid lines > do not show up. > > They say pictures are worth a thousand words, so I > took screen shots for the following variations of > my glFrustum call. > > /* This works correctly */ > glFrustum(0.00001,0.5,0.00001,0.5,1.0,20.0); > http://lothos.tool.net/planet_normal.jpg > > /* This does not */ > glFrustum(0.0,0.5,0.0,0.5,1.0,20.0); > http://lothos.tool.net/planet_bug.jpg > > I have also included the buggy version of my source > code as an attachment should anyone wish to try it > with their installation. I am running Mesa-3.4 on > Debian Linux (potato/stable), X version 3.3.6 OK, I found the problem. Basically, the problem occured when clipping a line for which one vertex was outside the clip volume and the other vertex was exactly on the clip boundary. I'm surprised that this didn't turn up long ago. Keith seemed to have already made the appropriate change for Mesa 3.5. The patch to Mesa-3.4/src/clip.c is: diff -r1.8 clip.c 304,311c304,305 < < #if 0 < #define NEGATIVE(x) ((*(int *)&x)<0) < #define DIFFERENT_SIGNS(a,b) ((a*b) < 0) < #else < #define NEGATIVE(x) (x < 0) < #define DIFFERENT_SIGNS(a,b) ((a*b) < 0) < #endif --- > #define NEGATIVE(x) ((x) < 0.0) > #define DIFFERENT_SIGNS(a, b) (((a) * (b)) <= 0.0 && ((a) != (b))) Or, wait for the 3.4.1 release which I'm planning for today (unless anymore last-minute issues come up). -Brian |
From: Carey F. C. <cf...@co...> - 2001-02-09 17:10:30
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On Fri, 9 Feb 2001, Brian Paul wrote: > > Or, wait for the 3.4.1 release which I'm planning for today (unless > anymore last-minute issues come up). > Brian, Does this release also contain the corrections for the problems that I was facing with the compilation of the motif widget set? I am still having some problems getting everything to compile. Thanks, Carey -- ====================================================================== <> Carey F. Cox, PhD | PHONE: (318) 257-3770 <> <> Assistant Professor | FAX: (318) 257-2306 <> <> Dept. of Mech. Eng. | EMAIL: cf...@co... <> <> Louisiana Tech University | WEB: http://www.latech.edu/~cfcox <> ====================================================================== |
From: Brian P. <br...@va...> - 2001-02-09 17:15:30
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"Carey F. Cox" wrote: > > On Fri, 9 Feb 2001, Brian Paul wrote: > > > > > Or, wait for the 3.4.1 release which I'm planning for today (unless > > anymore last-minute issues come up). > > > > Brian, > > Does this release also contain the corrections for the problems > that I was facing with the compilation of the motif widget set? > I am still having some problems getting everything to compile. Can you remind me what the problem is? I don't see it in the Mesa bug database. -Brian |
From: Brian P. <br...@va...> - 2001-02-09 17:18:07
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Brian Paul wrote: > > "Carey F. Cox" wrote: > > > > On Fri, 9 Feb 2001, Brian Paul wrote: > > > > > > > > Or, wait for the 3.4.1 release which I'm planning for today (unless > > > anymore last-minute issues come up). > > > > > > > Brian, > > > > Does this release also contain the corrections for the problems > > that I was facing with the compilation of the motif widget set? > > I am still having some problems getting everything to compile. > > Can you remind me what the problem is? I don't see it in the > Mesa bug database. Nevermind, I found your previous message. I had sent you a new copy of MesaDrawingArea.c to try out but didn't hear from you if that worked or not. -Brian |