| /** |
| * Test for exact point/line/polygon rasterization, or at least rasterization |
| * that fits the tolerance of the OpenGL spec. |
| * |
| * Brian Paul |
| * 9 Nov 2007 |
| */ |
| |
| /* |
| * Notes: |
| * - 'm' to cycle through point, hline, vline and quad drawing |
| * - Use cursor keys to translate coordinates (z to reset) |
| * - Resize window to check for proper rasterization |
| * - Make sure your LCD is running in its native resolution |
| * |
| * If translation is (0,0): |
| * a point will be drawn where x%2==0 and y%2==0, |
| * a horizontal line will be drawn where x%2==0, |
| * a vertical line will be drawn where y%2==0, |
| * for quads, pixels will be set where (x%4)!=3 and (y%4)!=3 |
| * |
| * XXX todo: do glReadPixels and test that the results are what's expected. |
| * Upon failure, iterate over sub-pixel translations to find the ideal offset. |
| */ |
| |
| |
| #include <stdio.h> |
| #include <stdlib.h> |
| #include <GL/glew.h> |
| #include <GL/glut.h> |
| |
| static int Width = 400, Height = 400; |
| static int Win; |
| static float Xtrans = 0, Ytrans = 0; |
| static float Step = 0.125; |
| |
| enum { |
| MODE_POINTS, |
| MODE_HLINES, |
| MODE_VLINES, |
| MODE_QUADS, |
| NUM_MODES |
| }; |
| |
| static int Mode = MODE_POINTS; |
| |
| |
| static void |
| Draw(void) |
| { |
| /* See the OpenGL Programming Guide, Appendix H, "OpenGL Correctness Tips" |
| * for information about the 0.375 translation factor. |
| */ |
| float tx = 0.375, ty = 0.375; |
| int i, j; |
| |
| glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); |
| |
| glPushMatrix(); |
| glTranslatef(tx + Xtrans, ty + Ytrans, 0); |
| |
| if (Mode == MODE_POINTS) { |
| glBegin(GL_POINTS); |
| for (j = 0; j < Height; j += 2) { |
| for (i = 0; i < Width; i += 2) { |
| glVertex2f(i, j); |
| } |
| } |
| glEnd(); |
| } |
| else if (Mode == MODE_HLINES) { |
| glBegin(GL_LINES); |
| for (i = 0; i < Height; i += 2) { |
| glVertex2f(0, i); |
| glVertex2f(Width, i); |
| } |
| glEnd(); |
| } |
| else if (Mode == MODE_VLINES) { |
| glBegin(GL_LINES); |
| for (i = 0; i < Width; i += 2) { |
| glVertex2f(i, 0 ); |
| glVertex2f(i, Height); |
| } |
| glEnd(); |
| } |
| else if (Mode == MODE_QUADS) { |
| glBegin(GL_QUADS); |
| for (j = 0; j < Height; j += 4) { |
| for (i = 0; i < Width; i += 4) { |
| glVertex2f(i, j ); |
| glVertex2f(i + 3, j ); |
| glVertex2f(i + 3, j + 3); |
| glVertex2f(i, j + 3); |
| } |
| } |
| glEnd(); |
| } |
| |
| glPopMatrix(); |
| |
| glutSwapBuffers(); |
| } |
| |
| |
| static void |
| Reshape(int width, int height) |
| { |
| Width = width; |
| Height = height; |
| glViewport(0, 0, width, height); |
| glMatrixMode(GL_PROJECTION); |
| glLoadIdentity(); |
| glOrtho(0, width, 0, height, -1, 1); |
| glMatrixMode(GL_MODELVIEW); |
| glLoadIdentity(); |
| } |
| |
| |
| static void |
| Key(unsigned char key, int x, int y) |
| { |
| (void) x; |
| (void) y; |
| switch (key) { |
| case 'm': |
| case 'M': |
| Mode = (Mode + 1) % NUM_MODES; |
| break; |
| case 'z': |
| case 'Z': |
| Xtrans = Ytrans = 0; |
| printf("Translation: %f, %f\n", Xtrans, Ytrans); |
| break; |
| case 27: |
| glutDestroyWindow(Win); |
| exit(0); |
| break; |
| } |
| glutPostRedisplay(); |
| } |
| |
| |
| static void |
| SpecialKey(int key, int x, int y) |
| { |
| (void) x; |
| (void) y; |
| switch (key) { |
| case GLUT_KEY_UP: |
| Ytrans += Step; |
| break; |
| case GLUT_KEY_DOWN: |
| Ytrans -= Step; |
| break; |
| case GLUT_KEY_LEFT: |
| Xtrans -= Step; |
| break; |
| case GLUT_KEY_RIGHT: |
| Xtrans += Step; |
| break; |
| } |
| glutPostRedisplay(); |
| printf("Translation: %f, %f\n", Xtrans, Ytrans); |
| } |
| |
| |
| static void |
| Init(void) |
| { |
| } |
| |
| |
| static void |
| Usage(void) |
| { |
| printf("Keys:\n"); |
| printf(" up/down/left/right - translate by %f\n", Step); |
| printf(" z - reset translation to zero\n"); |
| printf(" m - change rendering mode (points, hlines, vlines, quads)\n"); |
| printf(" Esc - exit\n"); |
| } |
| |
| |
| int |
| main(int argc, char *argv[]) |
| { |
| glutInit(&argc, argv); |
| glutInitWindowPosition(0, 0); |
| glutInitWindowSize(Width, Height); |
| glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE); |
| Win = glutCreateWindow(argv[0]); |
| glewInit(); |
| glutReshapeFunc(Reshape); |
| glutKeyboardFunc(Key); |
| glutSpecialFunc(SpecialKey); |
| glutDisplayFunc(Draw); |
| Init(); |
| Usage(); |
| glutMainLoop(); |
| return 0; |
| } |