/* accumaa.c - by Tom McReynolds, SGI */
/* Using the accumulation buffer for scene antialiasing. */
#include <GL/glut.h>
#include <stdlib.h>
#include <stdio.h>
const GLdouble FRUSTDIM = 100.f;
/* Create a single component texture map */
GLfloat *
make_texture(int maxs, int maxt)
{
int s, t;
static GLfloat *texture;
texture = (GLfloat *) malloc(maxs * maxt * sizeof(GLfloat));
for (t = 0; t < maxt; t++) {
for (s = 0; s < maxs; s++) {
texture[s + maxs * t] = ((s >> 4) & 0x1) ^ ((t >> 4) & 0x1);
}
}
return texture;
}
enum {
SPHERE = 1, CONE
};
void
render(void)
{
/* material properties for objects in scene */
static GLfloat wall_mat[] =
{1.f, 1.f, 1.f, 1.f};
glClear(GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT);
/* Note: wall verticies are ordered so they are all front facing this lets
me do back face culling to speed things up. */
glMaterialfv(GL_FRONT, GL_AMBIENT_AND_DIFFUSE, wall_mat);
/* floor */
/* make the floor textured */
glEnable(GL_TEXTURE_2D);
/* Since we want to turn texturing on for floor only, we have to make floor
a separate glBegin()/glEnd() sequence. You can't turn texturing on and
off between begin and end calls */
glBegin(GL_QUADS);
glNormal3f(0.f, 1.f, 0.f);
glTexCoord2i(0, 0);
glVertex3f(-100.f, -100.f, -320.f);
glTexCoord2i(1, 0);
glVertex3f(100.f, -100.f, -320.f);
glTexCoord2i(1, 1);
glVertex3f(100.f, -100.f, -520.f);
glTexCoord2i(0, 1);
glVertex3f(-100.f, -100.f, -520.f);
glEnd();
glDisable(GL_TEXTURE_2D);
/* walls */
glBegin(GL_QUADS);
/* left wall */
glNormal3f(1.f, 0.f, 0.f);
glVertex3f(-100.f, -100.f, -320.f);
glVertex3f(-100.f, -100.f, -520.f);
glVertex3f(-100.f, 100.f, -520.f);
glVertex3f(-100.f, 100.f, -320.f);
/* right wall */
glNormal3f(-1.f, 0.f, 0.f);
glVertex3f(100.f, -100.f, -320.f);
glVertex3f(100.f, 100.f, -320.f);
glVertex3f(100.f, 100.f, -520.f);
glVertex3f(100.f, -100.f, -520.f);
/* ceiling */
glNormal3f(0.f, -1.f, 0.f);
glVertex3f(-100.f, 100.f, -320.f);
glVertex3f(-100.f, 100.f, -520.f);
glVertex3f(100.f, 100.f, -520.f);
glVertex3f(100.f, 100.f, -320.f);
/* back wall */
glNormal3f(0.f, 0.f, 1.f);
glVertex3f(-100.f, -100.f, -520.f);
glVertex3f(100.f, -100.f, -520.f);
glVertex3f(100.f, 100.f, -520.f);
glVertex3f(-100.f, 100.f, -520.f);
glEnd();
glPushMatrix();
glTranslatef(-80.f, -60.f, -420.f);
glCallList(SPHERE);
glPopMatrix();
glPushMatrix();
glTranslatef(-20.f, -80.f, -500.f);
glCallList(CONE);
glPopMatrix();
if (glGetError()) /* to catch programming errors; should never happen */
printf("Oops! I screwed up my OpenGL calls somewhere\n");
glFlush(); /* high end machines may need this */
}
/* compute scale factor for window->object space transform could use
gluUnProject(), but probably too much trouble */
void
computescale(GLfloat * sx, GLfloat * sy)
{
enum {
XORG, YORG, WID, HT
};
GLint viewport[4];
glGetIntegerv(GL_VIEWPORT, viewport);
*sx = 2 * FRUSTDIM / viewport[WID];
*sy = 2 * FRUSTDIM / viewport[WID];
}
enum {
NONE, AA
};
int rendermode = NONE;
void
menu(int selection)
{
rendermode = selection;
glutPostRedisplay();
}
/* Called when window needs to be redrawn */
void
redraw(void)
{
int i, j;
int min, max;
int count;
GLfloat invx, invy;
GLfloat scale, dx, dy;
switch (rendermode) {
case NONE:
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glFrustum(-FRUSTDIM, FRUSTDIM, -FRUSTDIM, FRUSTDIM, 320., 640.);
glMatrixMode(GL_MODELVIEW);
render();
break;
case AA:
min = -2;
max = -min + 1;
count = -2 * min + 1;
count *= count;
/* uniform scaling, less than one pixel wide */
scale = -.9f / min;
computescale(&invx, &invy);
glClear(GL_ACCUM_BUFFER_BIT);
for (j = min; j < max; j++) {
for (i = min; i < max; i++) {
dx = invx * scale * i;
dy = invy * scale * j;
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glFrustum(-FRUSTDIM + dx,
FRUSTDIM + dy,
-FRUSTDIM + dx,
FRUSTDIM + dy,
320., 640.);
glMatrixMode(GL_MODELVIEW);
render();
glAccum(GL_ACCUM, 1.f / count);
}
}
glAccum(GL_RETURN, 1.f);
break;
}
glutSwapBuffers();
}
/* ARGSUSED1 */
void
key(unsigned char key, int x, int y)
{
if (key == '\033')
exit(0);
}
const int TEXDIM = 256;
/* Parse arguments, and set up interface between OpenGL and window system */
int
main(int argc, char *argv[])
{
GLfloat *tex;
static GLfloat lightpos[] =
{50.f, 50.f, -320.f, 1.f};
static GLfloat sphere_mat[] =
{1.f, .5f, 0.f, 1.f};
static GLfloat cone_mat[] =
{0.f, .5f, 1.f, 1.f};
GLUquadricObj *sphere, *cone, *base;
glutInit(&argc, argv);
glutInitWindowSize(512, 512);
glutInitDisplayMode(GLUT_RGBA | GLUT_DEPTH | GLUT_ACCUM | GLUT_DOUBLE);
(void) glutCreateWindow("scene antialiasing");
glutDisplayFunc(redraw);
glutKeyboardFunc(key);
glutCreateMenu(menu);
glutAddMenuEntry("Aliased View", NONE);
glutAddMenuEntry("AntiAliased", AA);
glutAttachMenu(GLUT_RIGHT_BUTTON);
/* draw a perspective scene */
glMatrixMode(GL_PROJECTION);
glFrustum(-FRUSTDIM, FRUSTDIM, -FRUSTDIM, FRUSTDIM, 320., 640.);
glMatrixMode(GL_MODELVIEW);
/* turn on features */
glEnable(GL_DEPTH_TEST);
glEnable(GL_LIGHTING);
glEnable(GL_LIGHT0);
/* place light 0 in the right place */
glLightfv(GL_LIGHT0, GL_POSITION, lightpos);
/* remove back faces to speed things up */
glCullFace(GL_BACK);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glNewList(SPHERE, GL_COMPILE);
/* make display lists for sphere and cone; for efficiency */
sphere = gluNewQuadric();
glMaterialfv(GL_FRONT, GL_AMBIENT_AND_DIFFUSE, sphere_mat);
gluSphere(sphere, 20.f, 20, 20);
gluDeleteQuadric(sphere);
glEndList();
glNewList(CONE, GL_COMPILE);
cone = gluNewQuadric();
base = gluNewQuadric();
glRotatef(-90.f, 1.f, 0.f, 0.f);
glMaterialfv(GL_FRONT, GL_AMBIENT_AND_DIFFUSE, cone_mat);
gluDisk(base, 0., 20., 20, 1);
gluCylinder(cone, 20., 0., 60., 20, 20);
gluDeleteQuadric(cone);
gluDeleteQuadric(base);
glEndList();
/* load pattern for current 2d texture */
tex = make_texture(TEXDIM, TEXDIM);
glTexImage2D(GL_TEXTURE_2D, 0, 1, TEXDIM, TEXDIM, 0, GL_RED, GL_FLOAT, tex);
free(tex);
glReadBuffer(GL_BACK); /* input to accum buffer */
glutMainLoop();
return 0; /* ANSI C requires main to return int. */
}