/* Demonstration of jittering to achieve the depth-of-field effect

Written by Caroline Geiersbach and Scott D. Anderson
scott.anderson@acm.org
Summer 2003
*/

#include <stdio.h>
#include <GL/glut.h>
#include <tw.h>
#include <math.h>

/* values for the camera.  compute near and far based on a bounding box of
(-5,5,-5,5,-5,5).*/
GLfloat fovy=90;
GLfloat ar=1;
GLfloat near=3.0;
GLfloat far=21.0;
GLfloat left=-3;
GLfloat right=3;
GLfloat bottom=-3;
GLfloat top=3;

void reshape(int width, int height) {
  glViewport(0,0,width,height);
}


/* Set up camera. Note that near, far, and focus remain fixed; all that
is modified with the accumulation buffer is the eye location.*/
void accCamera(GLfloat eyedx, GLfloat eyedy, GLfloat focus) { 
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(90,1,near,far);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    gluLookAt(0+eyedx,0+eyedy,0,0,0,focus,0,1,0);
}

/*Draw teapot at the location (x,y,z) with the color (red, green, blue) */
void drawObject(GLfloat x, GLfloat y, GLfloat z, GLfloat scale, 
                GLfloat red, GLfloat green, GLfloat blue) {
    glPushMatrix();
    glTranslatef(x,y,z);
    glScalef(scale,scale,scale);
    twTriple color = {red, green, blue};
    twColor(color,0.9,128.0);
    glBegin(GL_POLYGON);
    glVertex3f(-1,-1,0);
    glVertex3f(-1,1,0);
    glVertex3f(1,1,0);
    glVertex3f(1,-1,0);
    glEnd();
    glPopMatrix();
}                    

void display(void) {
    int jitter;
    int numJitters = 8;
    glClear(GL_ACCUM_BUFFER_BIT);
    for(jitter=0; jitter<numJitters; jitter++) { //draw scene 8 times
      glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
      accCamera(0.04*jitter,0.04*jitter,-6); //focus on green object
      drawObject(0,0,-4,1,1,0,0); //red
      drawObject(0,0,-6,3,0,1,0);   //green
      drawObject(0,0,-8,5,0,0,1);   //blue
      drawObject(0,0,-10,9,0,1,1);   //cyan
      glAccum(GL_ACCUM, 1.0/numJitters);
    }
    glAccum(GL_RETURN, 1.0);
    glFlush();
    glutSwapBuffers();
}

void myInit() {
  printf("version using gluPerspective and gluLookAt;only eye vals changed.\n");
    glEnable(GL_DEPTH_TEST);
    glEnable(GL_NORMALIZE);
    glEnable(GL_LEQUAL);

    //lighting
    GLfloat ambDiff[] = {1.0,1.0,1.0,1.0};
    GLfloat spec[] = {1.0,1.0,1.0,1.0};
    GLfloat position[] = {1.0,3.0,3.0,0.0};
    glLightfv(GL_LIGHT0, GL_AMBIENT_AND_DIFFUSE, ambDiff);
    glLightfv(GL_LIGHT0, GL_SPECULAR, spec);
    glLightfv(GL_LIGHT0, GL_POSITION, position);
    twAmbient(1.0);
    glLightModelf(GL_LIGHT_MODEL_LOCAL_VIEWER, 0.0);
    glEnable(GL_LIGHTING);
    glEnable(GL_LIGHT0);

    //clear
    glClearColor(0,0,0,0);
    glClearAccum(0,0,0,0);
}

int main(int argc, char** argv) {
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_ACCUM | GLUT_DEPTH);
    glutInitWindowSize(600,600);
    glutCreateWindow(argv[0]);
    glutReshapeFunc(reshape);
    glutDisplayFunc(display);
    myInit();
    glutMainLoop();
    return 0;
}