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