| /* |
| * Test the GL_PERSPECTIVE_CORRECTION_HINT setting and its effect on |
| * color interpolation. |
| * |
| * Press 'i' to toggle between GL_NICEST/GL_FASTEST/GL_DONT_CARE. |
| * |
| * Depending on the driver, the hint may make a difference, or not. |
| */ |
| |
| |
| #include <stdlib.h> |
| #include <stdio.h> |
| #include <GL/glut.h> |
| |
| |
| static GLenum PerspHint = GL_DONT_CARE; |
| |
| |
| static void |
| init(void) |
| { |
| GLubyte image[256][256][4]; |
| GLuint i, j; |
| for (i = 0; i < 256; i++) { |
| for (j = 0; j < 256; j++) { |
| image[i][j][0] = j; |
| image[i][j][1] = j; |
| image[i][j][2] = j; |
| image[i][j][3] = 255; |
| } |
| } |
| glTexImage2D(GL_TEXTURE_2D, 0, 4, 256, 256, 0, |
| GL_RGBA, GL_UNSIGNED_BYTE, image); |
| glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT); |
| glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT); |
| glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); |
| glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); |
| glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL); |
| |
| printf("GL_RENDERER = %s\n", (char *) glGetString(GL_RENDERER)); |
| } |
| |
| |
| static void |
| display(void) |
| { |
| switch (PerspHint) { |
| case GL_NICEST: |
| printf("hint = GL_NICEST\n"); |
| break; |
| case GL_FASTEST: |
| printf("hint = GL_FASTEST\n"); |
| break; |
| case GL_DONT_CARE: |
| printf("hint = GL_DONT_CARE\n"); |
| break; |
| default: |
| ; |
| } |
| |
| glClear(GL_COLOR_BUFFER_BIT); |
| |
| #if 1 |
| glBegin(GL_QUADS); |
| /* exercise perspective interpolation */ |
| glColor3f(0.0, 0.0, 0.0); glVertex3f(-1.0, -1.0, -1.0); |
| glColor3f(0.0, 0.0, 0.0); glVertex3f(-1.0, 1.0, -1.0); |
| glColor3f(0.0, 1.0, 0.0); glVertex3f( 7.0, 1.0, -7.0); |
| glColor3f(0.0, 1.0, 0.0); glVertex3f( 7.0, -1.0, -7.0); |
| |
| /* stripe of linear interpolation */ |
| glColor3f(0.0, 0.0, 0.0); glVertex3f(-1.0, -0.1, -1.001); |
| glColor3f(0.0, 0.0, 0.0); glVertex3f(-1.0, 0.1, -1.001); |
| glColor3f(0.0, 1.0, 0.0); glVertex3f( 1.0, 0.1, -1.001); |
| glColor3f(0.0, 1.0, 0.0); glVertex3f( 1.0, -0.1, -1.001); |
| glEnd(); |
| #else |
| glEnable(GL_TEXTURE_2D); |
| glBegin(GL_QUADS); |
| glTexCoord2f(0.0, 0.0); glVertex3f(-1.0, 0.0, -1.0); |
| glTexCoord2f(0.0, 1.0); glVertex3f(-1.0, 1.0, -1.0); |
| glTexCoord2f(1.0, 1.0); glVertex3f( 5.0, 1.0, -7.0); |
| glTexCoord2f(1.0, 0.0); glVertex3f( 5.0, 0.0, -7.0); |
| |
| glTexCoord2f(0.0, 0.0); glVertex3f(-1.0, -1.0, -1.001); |
| glTexCoord2f(0.0, 1.0); glVertex3f(-1.0, 0.0, -1.001); |
| glTexCoord2f(1.0, 1.0); glVertex3f( 1.0, 0.0, -1.001); |
| glTexCoord2f(1.0, 0.0); glVertex3f( 1.0, -1.0, -1.001); |
| glEnd(); |
| #endif |
| |
| glFlush(); |
| } |
| |
| |
| static void |
| reshape(int w, int h) |
| { |
| glViewport(0, 0, w, h); |
| glMatrixMode(GL_PROJECTION); |
| glLoadIdentity(); |
| gluPerspective(90.0, (GLfloat) w / h, 1.0, 300.0); |
| glMatrixMode(GL_MODELVIEW); |
| glLoadIdentity(); |
| } |
| |
| |
| static void |
| key(unsigned char k, int x, int y) |
| { |
| switch (k) { |
| case 27: /* Escape */ |
| exit(0); |
| break; |
| case 'i': |
| if (PerspHint == GL_FASTEST) |
| PerspHint = GL_NICEST; |
| else if (PerspHint == GL_NICEST) |
| PerspHint = GL_DONT_CARE; |
| else |
| PerspHint = GL_FASTEST; |
| glHint(GL_PERSPECTIVE_CORRECTION_HINT, PerspHint); |
| break; |
| default: |
| return; |
| } |
| glutPostRedisplay(); |
| } |
| |
| |
| int |
| main(int argc, char** argv) |
| { |
| glutInit(&argc, argv); |
| glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB); |
| glutInitWindowSize (500, 500); |
| glutCreateWindow (argv[0]); |
| glutReshapeFunc (reshape); |
| glutDisplayFunc(display); |
| glutKeyboardFunc(key); |
| |
| printf("Main quad: perspective projection\n"); |
| printf("Middle stripe: linear interpolation\n"); |
| printf("Press 'i' to toggle interpolation hint\n"); |
| init(); |
| |
| glutMainLoop(); |
| return 0; |
| } |