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Colby Toland
08-04-2004, 10:43 AM
I build a structure up from triangles (not strips) going down the y-axis along the x-axis. However the triangles drawn last appear on top whether they actually exist behind or in front.

Here is my code setting up the depth buffer:

glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
glDepthMask(GL_TRUE);
glClearDepth(1.0f);
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LEQUAL);

I clear the depth buffer one time before I draw the the object.

Any ideas on what could cause this?

Colby

plasmonster
08-04-2004, 01:51 PM
I would post the code that does the rendering, along with all the state changes you make.

Colby Toland
08-05-2004, 05:00 AM
I believe it is either a hardware or driver problem because my depth testing is not working period. The program below shows a red sphere in back, a green box in the middle, and a blue sphere in front... the order in which they are drawn not the order of their depth relative to the camera.


#include <GL\glut.h>

void display()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glViewport(0, 0, 800, 600);

glMatrixMode(GL_PROJECTION);
glLoadIdentity();

gluPerspective(45, 4/3, 0, 2);
gluLookAt(0, 0, 0, 0, 0, 1, 0, 1, 0);

glMatrixMode(GL_MODELVIEW);
glLoadIdentity();

glPushMatrix();
glColor3f(1, 0, 0);
glTranslatef(.05, .05, .5);

glutSolidSphere(.05, 20, 20);
glPopMatrix();

glPushMatrix();
glColor3f(0, 1, 0);
glTranslatef(0, 0, 1);

glutSolidCube(.1);
glPopMatrix();

glPushMatrix();
glColor3f(0, 0, 1);
glTranslatef(-.1, -.1, 1.5);

glutSolidSphere(.05, 20, 20);
glPopMatrix();

glutSwapBuffers();
}

int main(int argc, char ** argv)
{
glutInit(&amp;argc, argv);

glutInitDisplayMode(GLUT_DOUBLE | GLUT_DEPTH | GLUT_RGBA);
glutInitWindowSize(800, 600);
glutInitWindowPosition(0, 0);
glutCreateWindow("Demonstration");

glEnable(GL_LIGHTING);
GLfloat diffuseLight[] = {.75, .75, .75, 1};
GLfloat lightPosition[] = {-1, -1, -1, 1};
glLightfv(GL_LIGHT0, GL_DIFFUSE, diffuseLight);
glLightfv(GL_LIGHT0, GL_POSITION, lightPosition);
glEnable(GL_LIGHT0);

glEnable(GL_COLOR_MATERIAL);
glColorMaterial(GL_FRONT, GL_AMBIENT_AND_DIFFUSE);

glDepthMask(GL_TRUE);
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LEQUAL);

glShadeModel(GL_SMOOTH);

glClearColor(0, 0, 0, 0);

glutDisplayFunc(display);

glutMainLoop();

return 0;
}
My graphics card is a GeForce2 MX 400 and I'm using the Nvidia driver version 5.6.7.2 (released in March 2004). I also have Nvidia's latest stereo driver installed. I'm compiling the code in MS VC++ 6 on a WinXP system.

Has anyone seen this before?

Colby

08-05-2004, 06:18 AM
It amazes me everytime when I see someone questioning something that is proven to work for years.

Its quiet simple. The znear clipping plane must be a positive value (as in greater then zero) as defined in the manual.

So if you use:


gluPerspective(45, 4/3, 0.1, 2);everything will be fine.

Sumpfratte
08-05-2004, 06:29 AM
not fast enough, i wanted to post the same.

...by the way you should use 4.0/3 instead of 4/3 for the aspect ratio, because in c and c++ 4/3 = 1.

Colby Toland
08-05-2004, 08:08 AM
I should have realized that. Thanks.

08-05-2004, 12:59 PM
Originally posted by Sumpfratte:
not fast enough, i wanted to post the same.
:D


Originally posted by Sumpfratte:
...by the way you should use 4.0/3 instead of 4/3 for the aspect ratio, because in c and c++ 4/3 = 1.Right you are, I missed that.