OpenGL Help!

Wes_Poole · March 21, 2000, 11:45pm

I’m working on a quick OpenGL demo for SDL, basically I took the
aliens demo and dropped the resolution down to 256x256, then I mapped
it to an OpenGL texture and mapped that on a cube (well I borrowed
code to do that). The problem is it runs for about a second
(accelerated, 3 seconds under raw mesa because of lag) and then it
dies and mesa complains, but for the life of me I can’t figure out
what is causing the crash.

members.xoom.com/kokido/glaliens.html

has a link to the code

Phoenix Kokido
members.xoom.com/kokido
@Wes_Poole

Andreas_Umbach · March 22, 2000, 10:18am

Phoenix Kokido schrieb am 21 Mar 2000:

I’m working on a quick OpenGL demo for SDL, basically I took the
aliens demo and dropped the resolution down to 256x256, then I mapped
it to an OpenGL texture and mapped that on a cube (well I borrowed
code to do that).

Hm. I thought that code looks familiar

The problem is it runs for about a second
(accelerated, 3 seconds under raw mesa because of lag) and then it
dies and mesa complains, but for the life of me I can’t figure out
what is causing the crash.

In your attempt to keep aliens from having 666 lines you accidently deleted
a ‘numupdates = 0;’ line, resulting in an array index out-of-bound. The
attached patch fixes that problem and another one:

It’s not a good idea to generate a new texture ID every frame. You will
quickly eat all available memory. Generate the texture ID once and reuse
it, if you don’t need the old texture contents anymore.

Andreas–
Probably one of the smallest 3D-Games in the world: http://www.gltron.org
More than 60’000 Downloads of the latest version (0.53)
-------------- next part --------------
*** aliens.c.orig Wed Mar 22 11:13:34 2000
— aliens.c Wed Mar 22 11:15:53 2000

*** 154,161 ****
format = (bpp == 24) ? GL_RGB : GL_RGBA;

/* load the texture into OGL */

! glGenTextures(1, &tex_id);
! glBindTexture(GL_TEXTURE_2D, tex_id);
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glTexImage2D(GL_TEXTURE_2D, 0, format, image->w, image->h, 0,
format, GL_UNSIGNED_BYTE, data);
— 154,160 ----
format = (bpp == 24) ? GL_RGB : GL_RGBA;

/* load the texture into OGL */

!
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glTexImage2D(GL_TEXTURE_2D, 0, format, image->w, image->h, 0,
format, GL_UNSIGNED_BYTE, data);

*** 331,337 ****
screen, blits[i].dstrect);
}
SDL_UpdateRects(screen, numupdates, dstupdate);
! //ConvertTexture(screen);

glClearColor(0, 0, 0.5, 0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

— 330,337 ----
screen, blits[i].dstrect);
}
SDL_UpdateRects(screen, numupdates, dstupdate);
! numupdates = 0;
! ConvertTexture(screen);

glClearColor(0, 0, 0.5, 0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

*** 603,608 ****
— 603,609 ----

main(int argc, char *argv[])
{

```
    int tex_id;
```
/* Initialize the SDL library */
if ( SDL_Init(SDL_INIT_AUDIO|SDL_INIT_VIDEO) < 0 ) {
fprintf(stderr, “Couldn’t initialize SDL: %s\n”,SDL_GetError());

*** 635,640 ****
— 636,644 ----
gluLookAt(0, 0, 2,
0, 0, 0,
0, 1, 0);
+

glGenTextures(1, &tex_id);
glBindTexture(GL_TEXTURE_2D, tex_id);

screen=SDL_CreateRGBSurface(SDL_SWSURFACE, 256, 256, 24, 0,
0,

Wes_Poole · March 22, 2000, 1:02pm

I was pretty sure I had done something very stupid, thanks for
helping. I actually thought that the problem might have been related
to using all my available texture memory at one time, but now I see
that my code never actually ran that long.