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Diffstat (limited to 'progs/demos/singlebuffer.c')
| -rw-r--r-- | progs/demos/singlebuffer.c | 269 |
1 files changed, 269 insertions, 0 deletions
diff --git a/progs/demos/singlebuffer.c b/progs/demos/singlebuffer.c new file mode 100644 index 00000000000..9899c245b2a --- /dev/null +++ b/progs/demos/singlebuffer.c @@ -0,0 +1,269 @@ +/* + * 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; +} |