The teapots are drawn several times into the accumulation buffer.
The viewing volume is jittered, except at the focal point, where the viewing volume is at the same position, each time.
In this case, the gold teapot remains in focus.
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Shoreline Blvd., Mountain View, CA 94039-7311. * * OpenGL(TM) is a trademark of Silicon Graphics, Inc. */ #include <GL/openglut.h> #include <stdlib.h> #include <math.h> #include "jitter.h" #define PI_ 3.14159265358979323846 /* accFrustum() * The first 6 arguments are identical to the glFrustum() call. * * pixdx and pixdy are anti-alias jitter in pixels. * Set both equal to 0.0 for no anti-alias jitter. * eyedx and eyedy are depth-of field jitter in pixels. * Set both equal to 0.0 for no depth of field effects. * * focus is distance from eye to plane in focus. * focus must be greater than, but not equal to 0.0. * * Note that accFrustum() calls glTranslatef(). You will * probably want to insure that your ModelView matrix has been * initialized to identity before calling accFrustum(). */ void accFrustum(GLdouble left, GLdouble right, GLdouble bottom, GLdouble top, GLdouble nnear, GLdouble ffar, GLdouble pixdx, GLdouble pixdy, GLdouble eyedx, GLdouble eyedy, GLdouble focus) { GLdouble xwsize, ywsize; GLdouble dx, dy; GLint viewport[4]; glGetIntegerv (GL_VIEWPORT, viewport); xwsize = right - left; ywsize = top - bottom; dx = -(pixdx*xwsize/(GLdouble) viewport[2] + eyedx*nnear/focus); dy = -(pixdy*ywsize/(GLdouble) viewport[3] + eyedy*nnear/focus); glMatrixMode(GL_PROJECTION); glLoadIdentity(); glFrustum (left + dx, right + dx, bottom + dy, top + dy, nnear, ffar); glMatrixMode(GL_MODELVIEW); glLoadIdentity(); glTranslatef (-eyedx, -eyedy, 0.0); } /* accPerspective() * * The first 4 arguments are identical to the gluPerspective() call. * pixdx and pixdy are anti-alias jitter in pixels. * Set both equal to 0.0 for no anti-alias jitter. * eyedx and eyedy are depth-of field jitter in pixels. * Set both equal to 0.0 for no depth of field effects. * * focus is distance from eye to plane in focus. * focus must be greater than, but not equal to 0.0. * * Note that accPerspective() calls accFrustum(). */ void accPerspective(GLdouble fovy, GLdouble aspect, GLdouble nnear, GLdouble ffar, GLdouble pixdx, GLdouble pixdy, GLdouble eyedx, GLdouble eyedy, GLdouble focus) { GLdouble fov2,left,right,bottom,top; fov2 = ((fovy*PI_) / 180.0) / 2.0; top = nnear / (cos(fov2) / sin(fov2)); bottom = -top; right = top * aspect; left = -right; accFrustum (left, right, bottom, top, nnear, ffar, pixdx, pixdy, eyedx, eyedy, focus); } void myinit(void) { GLfloat ambient[] = { 0.0, 0.0, 0.0, 1.0 }; GLfloat diffuse[] = { 1.0, 1.0, 1.0, 1.0 }; GLfloat position[] = { 0.0, 3.0, 3.0, 0.0 }; GLfloat lmodel_ambient[] = { 0.2, 0.2, 0.2, 1.0 }; GLfloat local_view[] = { 0.0 }; glEnable(GL_DEPTH_TEST); glDepthFunc(GL_LESS); glLightfv(GL_LIGHT0, GL_AMBIENT, ambient); glLightfv(GL_LIGHT0, GL_DIFFUSE, diffuse); glLightfv(GL_LIGHT0, GL_POSITION, position); glLightModelfv(GL_LIGHT_MODEL_AMBIENT, lmodel_ambient); glLightModelfv(GL_LIGHT_MODEL_LOCAL_VIEWER, local_view); glFrontFace (GL_CW); glEnable(GL_LIGHTING); glEnable(GL_LIGHT0); glEnable(GL_AUTO_NORMAL); glEnable(GL_NORMALIZE); glMatrixMode (GL_MODELVIEW); glLoadIdentity (); glClearColor(0.0, 0.0, 0.0, 0.0); glClearAccum(0.0, 0.0, 0.0, 0.0); } void renderTeapot (GLfloat x, GLfloat y, GLfloat z, GLfloat ambr, GLfloat ambg, GLfloat ambb, GLfloat difr, GLfloat difg, GLfloat difb, GLfloat specr, GLfloat specg, GLfloat specb, GLfloat shine) { float mat[4]; glPushMatrix(); glTranslatef (x, y, z); mat[0] = ambr; mat[1] = ambg; mat[2] = ambb; mat[3] = 1.0; glMaterialfv (GL_FRONT, GL_AMBIENT, mat); mat[0] = difr; mat[1] = difg; mat[2] = difb; glMaterialfv (GL_FRONT, GL_DIFFUSE, mat); mat[0] = specr; mat[1] = specg; mat[2] = specb; glMaterialfv (GL_FRONT, GL_SPECULAR, mat); glMaterialf (GL_FRONT, GL_SHININESS, shine*128.0); glutSolidTeapot(0.5); glPopMatrix(); } /* display() draws 5 teapots into the accumulation buffer * several times; each time with a jittered perspective. * The focal point is at z = 5.0, so the gold teapot will * stay in focus. The amount of jitter is adjusted by the * magnitude of the accPerspective() jitter; in this example, 0.33. * In this example, the teapots are drawn 8 times. See jitter.h */ void display(void) { int jitter; GLint viewport[4]; glGetIntegerv (GL_VIEWPORT, viewport); glClear(GL_ACCUM_BUFFER_BIT); for (jitter = 0; jitter < 8; jitter++) { glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); accPerspective (45.0, (GLdouble) viewport[2]/(GLdouble) viewport[3], 1.0, 15.0, 0.0, 0.0, 0.33*j8[jitter].x, 0.33*j8[jitter].y, 5.0); /* ruby, gold, silver, emerald, and cyan teapots */ renderTeapot (-1.1, -0.5, -4.5, 0.1745, 0.01175, 0.01175, 0.61424, 0.04136, 0.04136, 0.727811, 0.626959, 0.626959, 0.6); renderTeapot (-0.5, -0.5, -5.0, 0.24725, 0.1995, 0.0745, 0.75164, 0.60648, 0.22648, 0.628281, 0.555802, 0.366065, 0.4); renderTeapot (0.2, -0.5, -5.5, 0.19225, 0.19225, 0.19225, 0.50754, 0.50754, 0.50754, 0.508273, 0.508273, 0.508273, 0.4); renderTeapot (1.0, -0.5, -6.0, 0.0215, 0.1745, 0.0215, 0.07568, 0.61424, 0.07568, 0.633, 0.727811, 0.633, 0.6); renderTeapot (1.8, -0.5, -6.5, 0.0, 0.1, 0.06, 0.0, 0.50980392, 0.50980392, 0.50196078, 0.50196078, 0.50196078, .25); glAccum (GL_ACCUM, 0.125); } glAccum (GL_RETURN, 1.0); glFlush(); } void myReshape(int w, int h) { glViewport(0, 0, w, h); } static void key(unsigned char k, int x, int y) { switch (k) { case 27: /* Escape */ exit(0); break; default: return; } glutPostRedisplay(); } /* Main Loop * Open window with initial window size, title bar, * RGBA display mode, depth buffer, and handle input events. */ int main(int argc, char** argv) { glutInit(&argc, argv); glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB | GLUT_ACCUM | GLUT_DEPTH); glutCreateWindow (argv[0]); myinit(); glutReshapeFunc(myReshape); glutDisplayFunc(display); glutKeyboardFunc(key); glutMainLoop(); return 0; /* ANSI C requires main to return int. */ }