[Mesa-dev] [Mesa-bug] distorted textures

[Raul Alonso]

    I don't know whether this is really a bug but i get distorted
textures when trying to render big quads located very far away from the
camera. I'm including a proggy that behaves that way on every Mesa
version i've tested (using the FXdriver on a Voodoo Graphics board).

    The weird thing with this proggy is that it works fine with
Microsoft software-only driver and NVIDIA OpenGL (TNT board).



#include <GL/glut.h>
#include <stdlib.h>
#include <stdio.h>
#include <math.h>

/* Create checkerboard texture */
#define checkImageWidth 64
#define checkImageHeight 64
static GLubyte checkImage[checkImageHeight][checkImageWidth][4];
static GLubyte otherImage[checkImageHeight][checkImageWidth][4];

static GLuint texName[2];

void makeCheckImages(void)
{
   int i, j, c;

   for (i = 0; i < checkImageHeight; i++) {
      for (j = 0; j < checkImageWidth; j++) {
         c = ((((i&0x8)==0)^((j&0x8)==0)))*255;
         checkImage[i][j][0] = (GLubyte) c;
         checkImage[i][j][1] = (GLubyte) c;
         checkImage[i][j][2] = (GLubyte) c;
         checkImage[i][j][3] = (GLubyte) 255;
         c = ((((i&0x10)==0)^((j&0x10)==0)))*255;
         otherImage[i][j][0] = (GLubyte) c;
         otherImage[i][j][1] = (GLubyte) 0;
         otherImage[i][j][2] = (GLubyte) 0;
         otherImage[i][j][3] = (GLubyte) 255;
      }
   }
}

void init(void)
{
   glClearColor (0.0, 0.0, 0.0, 0.0);
   glShadeModel(GL_FLAT);
   glEnable(GL_DEPTH_TEST);

   makeCheckImages();
   glPixelStorei(GL_UNPACK_ALIGNMENT, 1);

   glGenTextures(2, texName);
   glBindTexture(GL_TEXTURE_2D, texName[0]);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER,
                   GL_NEAREST);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,
                   GL_NEAREST);
   glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, checkImageWidth,
                checkImageHeight, 0, GL_RGBA, GL_UNSIGNED_BYTE,
                checkImage);

   glBindTexture(GL_TEXTURE_2D, texName[1]);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
   glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);
   glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, checkImageWidth,
                checkImageHeight, 0, GL_RGBA, GL_UNSIGNED_BYTE,
                otherImage);
   glEnable(GL_TEXTURE_2D);
}

void display(void)
{
#define NUM_QUADS 32
#define DEG2RAD(x) ((x)*3.14159265358979323846/180.0)
#define RADIUS 100000000.0

   static int i;
   static double angle=0.0;

   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
   glLoadIdentity();
   glBindTexture(GL_TEXTURE_2D, texName[0]);
   glRotatef(angle,0.0,1.0,0.0);
   angle+=0.01;

   for (i=0;i<NUM_QUADS;i++) {

#define X1 (RADIUS*0.9*cos(DEG2RAD(i*(360.0/NUM_QUADS))))
#define Z1 (RADIUS*0.9*sin(DEG2RAD(i*(360.0/NUM_QUADS))))
#define X2 (RADIUS*0.9*cos(DEG2RAD((i+1)*(360.0/NUM_QUADS))))
#define Z2 (RADIUS*0.9*sin(DEG2RAD((i+1)*(360.0/NUM_QUADS))))

        glBegin(GL_QUADS);
        glTexCoord2f(1.0,1.0);      glVertex3f(X2, RADIUS/5.0, Z2);
        glTexCoord2f(0.0,1.0);      glVertex3f(X1, RADIUS/5.0, Z1);
        glTexCoord2f(0.0,0.0);      glVertex3f(X1, -RADIUS/5.0, Z1);
        glTexCoord2f(1.0,0.0);      glVertex3f(X2, -RADIUS/5.0, Z2);
        glEnd();
   }
   glutSwapBuffers();
}

void reshape(int w, int h)
{
   glViewport(0, 0, (GLsizei) w, (GLsizei) h);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   gluPerspective(45.0, (GLfloat) w/(GLfloat) h, 1000.0, 100000000.0);
   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();
}

/* ARGSUSED1 */
void keyboard(unsigned char key, int x, int y)
{
   switch (key) {
      case 27:
         exit(0);
         break;
   }
}

void idle(void)
{
 glutPostRedisplay();
}


int main(int argc, char** argv)
{
   glutInit(&argc, argv);
   glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
   glutInitWindowSize(640, 480);
   glutInitWindowPosition(100, 100);
   glutCreateWindow(argv[0]);
   init();
   glutReshapeFunc(reshape);
   glutDisplayFunc(display);
   glutKeyboardFunc (keyboard);
   glutIdleFunc(idle);
   glutMainLoop();
   return 0;
}




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