ATI's fglrx linux driver and the depthbuffer

Started by vanbirk July 26, 2004 11:29 AM

5 comments, last by Ravuya 20 years, 6 months ago

Author

122

July 26, 2004 11:29 AM

Hi, I recently managed to get the driver working on a nForce2 board and an ATI Radeon 9600XT. Question: Did anyone ever try to read a value from the depthbuffer with this driver ? I wonder if it's only my setup, but under windows it works fine ... The issue is that when I try to read a depthbuffer value with glReadPixels(), it returns a wrong value everytime. For example, on a freshly cleared depthbuffer with ranges from [0, 1] it should return a "1" at every location, but nope, it returns something like 0.0396... . It also returns wrong values if I read back the whole depthbuffer. So if anyone could be so kind who has the 3.7.6 or 3.7.9 drivers from ATI installed to read back a single value ;)


#include <iostream>
using namespace std;

#include <GL/gl.h>
#include <GL/glu.h>
#include <GL/glut.h>

void idle( void ) {}
void reshape( int w, int h ) {}
void display( void )
{
  float val;
  glClearDepth( 1 );
  glClear( GL_DEPTH_BUFFER_BIT );
  glReadPixels( 0, 0, 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT, &val );
  cout << "Read: " << val << endl;
  exit( 0 );
}

int main( int argc, char **argv )
{
  glutInit( &argc, argv );
  glutInitWindowPosition( 100, 100 );
  glutInitWindowSize( 256, 256 );
  glutInitDisplayMode( GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH );
  glutCreateWindow( "depth test" );
  glutReshapeFunc( reshape );
  glutDisplayFunc( display );
  glutIdleFunc( idle );
  glutMainLoop();
}

The program is written from scratch for testing purposes and compiles. It should return "Read: 1.0" but returns 0.0369...and so forth.

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666_1337

122

July 27, 2004 03:56 AM

shouldn't you call glFlush or glFinish before trying to read from the graphics memory?

our new version has many new and good features. sadly, the good ones are not new and the new ones are not good

Malone1234

139

July 29, 2004 11:58 AM

Hey could you post a link or something to tell us how you got ATI's driver to work on an nForce2 in Linux? You will be my personal hero!

Brother Bob

10,350

July 29, 2004 01:16 PM

Quote:
Original post by 666_1337
shouldn't you call glFlush or glFinish before trying to read from the graphics memory?

No, there's no need for that.

Drevay

100

August 01, 2004 02:59 AM

ATi's fglrx drivers suck ASS. They're releasing a revamped version eventually, but compared to nVidia's, they suck.

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Ravuya

136

August 03, 2004 08:46 AM

Quote:
Original post by Drevay
ATi's fglrx drivers suck ASS. They're releasing a revamped version eventually, but compared to nVidia's, they suck.

I concur. It's nice to see the expensive video card you have get reduced to nothing more than a cheap framebuffer; ATI's drivers suck so much on 3D acceleration it's not funny.

ATI's fglrx linux driver and the depthbuffer

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ATI's fglrx linux driver and the depthbuffer

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