| /* |
| * Demo of (nearly) flicker-free drawing with a single color buffer. |
| * |
| * Basically, draw the scene into the Z buffer first, then draw the |
| * scene into the color buffer. Finally, "clear" the background by |
| * setting the fragments we didn't hit earlier. |
| * |
| * This won't work if you need blending. The technique works best |
| * when the scene is relatively simple and can be rendered quickly |
| * (i.e. with hardware), and when the objects don't move too much from |
| * one frame to the next. |
| * |
| * Brian Paul |
| * 25 August 2005 |
| * |
| * See Mesa license for terms. |
| */ |
| |
| |
| #include <stdio.h> |
| #include <stdlib.h> |
| #include <GL/glut.h> |
| |
| |
| #define FLICKER 0 |
| #define NO_FLICKER 1 |
| |
| static GLint Mode = NO_FLICKER; |
| static GLfloat Xrot = 0, Yrot = 0, Zrot = 0; |
| static GLboolean Anim = GL_TRUE; |
| static GLfloat ClearColor[4] = {0.2, 0.2, 0.9, 0.0}; |
| static GLfloat NearClip = 5.0, FarClip = 25.0, ViewDist = 7.0; |
| static double PrevTime = -1; |
| |
| struct box { |
| float tx, ty, tz; |
| float rx, ry, rz, ra; |
| float sx, sy, sz; |
| float color[4]; |
| }; |
| |
| #define NUM_BOXES 25 |
| |
| struct box Boxes[NUM_BOXES]; |
| |
| |
| /* Return random float in [0,1] */ |
| static float |
| Random(void) |
| { |
| int i = rand(); |
| return (float) (i % 1000) / 1000.0; |
| } |
| |
| |
| static void |
| MakeBoxes(void) |
| { |
| int i; |
| for (i = 0; i < NUM_BOXES; i++) { |
| Boxes[i].tx = -1.0 + 2.0 * Random(); |
| Boxes[i].ty = -1.0 + 2.0 * Random(); |
| Boxes[i].tz = -1.0 + 2.0 * Random(); |
| Boxes[i].sx = 0.1 + Random() * 0.4; |
| Boxes[i].sy = 0.1 + Random() * 0.4; |
| Boxes[i].sz = 0.1 + Random() * 0.4; |
| Boxes[i].rx = Random(); |
| Boxes[i].ry = Random(); |
| Boxes[i].rz = Random(); |
| Boxes[i].ra = Random() * 360.0; |
| Boxes[i].color[0] = Random(); |
| Boxes[i].color[1] = Random(); |
| Boxes[i].color[2] = Random(); |
| Boxes[i].color[3] = 1.0; |
| } |
| } |
| |
| |
| static void |
| DrawBoxes(void) |
| { |
| int i; |
| for (i = 0; i < NUM_BOXES; i++) { |
| glPushMatrix(); |
| glTranslatef(Boxes[i].tx, Boxes[i].ty, Boxes[i].tz); |
| glRotatef(Boxes[i].ra, Boxes[i].rx, Boxes[i].ry, Boxes[i].rz); |
| glScalef(Boxes[i].sx, Boxes[i].sy, Boxes[i].sz); |
| glMaterialfv(GL_FRONT, GL_AMBIENT_AND_DIFFUSE, Boxes[i].color); |
| glutSolidCube(1.0); |
| glPopMatrix(); |
| } |
| } |
| |
| |
| static void |
| Idle(void) |
| { |
| double dt, t = glutGet(GLUT_ELAPSED_TIME) * 0.001; |
| if (PrevTime < 0.0) |
| PrevTime = t; |
| dt = t - PrevTime; |
| PrevTime = t; |
| Xrot += 16.0 * dt; |
| Yrot += 12.0 * dt; |
| Zrot += 8.0 * dt; |
| glutPostRedisplay(); |
| } |
| |
| |
| static void |
| Draw(void) |
| { |
| if (Mode == FLICKER) { |
| glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); |
| } |
| else { |
| /* don't clear color buffer */ |
| glClear(GL_DEPTH_BUFFER_BIT); |
| /* update Z buffer only */ |
| glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE); |
| } |
| |
| glPushMatrix(); |
| glRotatef(Xrot, 1, 0, 0); |
| glRotatef(Yrot, 0, 1, 0); |
| glRotatef(Zrot, 0, 0, 1); |
| |
| DrawBoxes(); |
| |
| if (Mode == NO_FLICKER) { |
| /* update color buffer now */ |
| glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE); |
| glDepthFunc(GL_EQUAL); |
| DrawBoxes(); |
| glDepthFunc(GL_LESS); |
| } |
| |
| glPopMatrix(); |
| |
| if (Mode == NO_FLICKER) { |
| /* "clear" the untouched pixels now. |
| * Note: if you comment-out this code you'll see something interesting. |
| */ |
| GLfloat x = FarClip / NearClip; |
| GLfloat z = -(FarClip - ViewDist - 1.0); |
| glDisable(GL_LIGHTING); |
| glColor4fv(ClearColor); |
| glBegin(GL_POLYGON); |
| glVertex3f(-x, -x, z); |
| glVertex3f( x, -x, z); |
| glVertex3f( x, x, z); |
| glVertex3f(-x, x, z); |
| glEnd(); |
| glEnable(GL_LIGHTING); |
| } |
| |
| /* This is where you'd normally do SwapBuffers */ |
| glFinish(); |
| } |
| |
| |
| static void |
| Reshape(int width, int height) |
| { |
| glViewport(0, 0, width, height); |
| glMatrixMode(GL_PROJECTION); |
| glLoadIdentity(); |
| glFrustum(-1.0, 1.0, -1.0, 1.0, NearClip, FarClip); |
| glMatrixMode(GL_MODELVIEW); |
| glLoadIdentity(); |
| glTranslatef(0.0, 0.0, -ViewDist); |
| } |
| |
| |
| static void |
| Key(unsigned char key, int x, int y) |
| { |
| (void) x; |
| (void) y; |
| switch (key) { |
| case 'a': |
| Anim = !Anim; |
| if (Anim) |
| glutIdleFunc(Idle); |
| else |
| glutIdleFunc(NULL); |
| PrevTime = -1; |
| break; |
| case 'm': |
| Mode = !Mode; |
| break; |
| case 'b': |
| MakeBoxes(); |
| break; |
| case 27: |
| exit(0); |
| break; |
| } |
| glutPostRedisplay(); |
| } |
| |
| |
| static void |
| SpecialKey(int key, int x, int y) |
| { |
| const GLfloat step = 3.0; |
| (void) x; |
| (void) y; |
| switch (key) { |
| case GLUT_KEY_UP: |
| Xrot -= step; |
| break; |
| case GLUT_KEY_DOWN: |
| Xrot += step; |
| break; |
| case GLUT_KEY_LEFT: |
| Yrot -= step; |
| break; |
| case GLUT_KEY_RIGHT: |
| Yrot += step; |
| break; |
| } |
| glutPostRedisplay(); |
| } |
| |
| |
| static void |
| Init(void) |
| { |
| glClearColor(ClearColor[0], ClearColor[1], ClearColor[2], ClearColor[3]); |
| glEnable(GL_DEPTH_TEST); |
| glEnable(GL_LIGHTING); |
| glEnable(GL_LIGHT0); |
| glEnable(GL_CULL_FACE); |
| glEnable(GL_NORMALIZE); |
| MakeBoxes(); |
| } |
| |
| |
| static void |
| Usage(void) |
| { |
| printf("Keys:\n"); |
| printf(" m - toggle drawing mode (flicker vs. no flicker)\n"); |
| printf(" a - toggle animation\n"); |
| printf(" b - generate new boxes\n"); |
| printf(" ARROWS - rotate scene\n"); |
| printf(" ESC - exit\n"); |
| } |
| |
| |
| int |
| main(int argc, char *argv[]) |
| { |
| glutInit(&argc, argv); |
| glutInitWindowSize(800, 800); |
| glutInitDisplayMode(GLUT_RGB | GLUT_SINGLE | GLUT_DEPTH); |
| glutCreateWindow(argv[0]); |
| glutReshapeFunc(Reshape); |
| glutKeyboardFunc(Key); |
| glutSpecialFunc(SpecialKey); |
| glutDisplayFunc(Draw); |
| if (Anim) |
| glutIdleFunc(Idle); |
| Init(); |
| Usage(); |
| glutMainLoop(); |
| return 0; |
| } |