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authorBrian Paul <brian.paul@tungstengraphics.com>2005-08-25 23:25:25 +0000
committerBrian Paul <brian.paul@tungstengraphics.com>2005-08-25 23:25:25 +0000
commit59d680db22572a4ec3780b6bf12f82c50099ec98 (patch)
tree990bf3948afb1bf1762ae40468cbadc56923f21f /progs/demos
parent713635adef160b6dffaa929a00bfd72703f0b873 (diff)
Demo of how to do (nearly) flicker-free rendering with a single color buffer.
Diffstat (limited to 'progs/demos')
-rw-r--r--progs/demos/Makefile1
-rw-r--r--progs/demos/singlebuffer.c269
2 files changed, 270 insertions, 0 deletions
diff --git a/progs/demos/Makefile b/progs/demos/Makefile
index 4bd72d8a5c..109d0aca91 100644
--- a/progs/demos/Makefile
+++ b/progs/demos/Makefile
@@ -44,6 +44,7 @@ PROGS = \
reflect \
renormal \
shadowtex \
+ singlebuffer \
spectex \
spriteblast \
stex3d \
diff --git a/progs/demos/singlebuffer.c b/progs/demos/singlebuffer.c
new file mode 100644
index 0000000000..9899c245b2
--- /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;
+}