I am seeing rendering errors on two GeForce cards. Front faces are being culled or clipped inapproipriately. I am trying to understand whether I am doing something wrong.
I know it’s not usually good form to post C code, but this is a simple demo that most anyone on this forum should be able to compile.
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#include <GL/gl.h>
#include <GL/glu.h>
#include <GL/glut.h>
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
// Useful Constants
#define PI 3.14159
#define NEAR_CUTOFF 4.0
#define FAR_CUTOFF 80000.0
#define FOV_Y 60.0
void printInstructions(void){
// Print a summary of the user-interface.
printf("This program demonstrates a bug in the torus rendering.
“);
printf(” * ‘Esc’ quits the program
“);
printf(”
");
}
void display(void)
{
// Set up the view matrix.
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
float viewMatrix[16] = {
-0.098, -0.882, -0.460, 0.000,
-0.995, 0.087, 0.045, 0.000,
-0.000, 0.462, -0.887, 0.000,
1312.500, 1628.035, 43550.770, 1.000};
glMultMatrixf(viewMatrix);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// Draw an object at the origin
// glShadeModel (GL_SMOOTH);
glShadeModel (GL_FLAT);
GLfloat mat_specular[] = { 1.0, 1.0, 1.0, 1.0 };
GLfloat mat_shininess[] = { 70.0 };
GLfloat light_position[] = { 0.0, -100000.0, 100000.0, 0.0 };
glMaterialfv(GL_FRONT, GL_SPECULAR, mat_specular);
glMaterialfv(GL_FRONT, GL_SHININESS, mat_shininess);
glEnable(GL_LIGHTING);
glLightfv(GL_LIGHT0, GL_POSITION, light_position);
glEnable(GL_LIGHT0);
glEnable(GL_DEPTH_TEST);
glutSolidTorus(3000, 10000, 15, 42);
// glutWireTorus (3000, 10000, 15, 42);
glutSwapBuffers();
int i = glGetError();
printf ("after glutSwapBuffers(), glGetError() returned %d
", i);
}
void reshape(int w, int h)
// Called when window changes dimensions. Set up viewport & projection matrix.
//
// Reshape the display using manual vector computations instead of gluPerspective
{
glViewport(0, 0, (GLsizei)w, (GLsizei)h);
//
// Set up projection matrix.
// This is slightly non-standard, since I prefer right-handed
// view coordinates, while OpenGL defaults to a left-handed system.
//
float nearz = NEAR_CUTOFF;
float farz = FAR_CUTOFF;
float fovy = FOV_Y;
float AspectRatio = float(h) / float(w);
float ViewAngleH = fovy * (PI / 180);
float ViewAngleV = atan(tan(ViewAngleH/2) * AspectRatio) * 2;
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
float m[16];
int i;
for (i = 0; i < 16; i++) m[i] = 0;
m[0] = -1.0 / tan(ViewAngleH / 2);
m[5] = -m[0] / AspectRatio;
m[10] = (farz + nearz) / (farz - nearz);
m[11] = 1;
m[14] = - 2 * farz * nearz / (farz - nearz);
glMultMatrixf(m);
// gluPerspective(fovy, (GLfloat) w/(GLfloat) h, nearz, farz);
glMatrixMode(GL_MODELVIEW);
}
void keyboard (unsigned char key, int x, int y)
{
switch (key) {
case 27:
exit(0);
break;
default:
printf ("Key pressed: %d
", key);
break;
}
}
int main(int argc, char** argv)
{
printInstructions();
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
glEnable (GL_DEPTH_TEST);
glutInitWindowSize(250, 250);
glutInitWindowPosition(100, 100);
glutCreateWindow(argv[0]);
glutDisplayFunc(display);
glutReshapeFunc(reshape);
glutKeyboardFunc(keyboard);
glutMainLoop();
return 0;
}