/* Demonstrates the use of shadows */

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


/* set up yellow light from origin */
void lighting() {
  GLfloat lightPosition [] = {0,0,0,1.0}; //point light source at origin
  GLfloat ambient [] = {1,1,0,1};
  GLfloat diffuse [] = {1,1,0,1};
  GLfloat specular [] = {1,1,1,1};
  glShadeModel(GL_FLAT);
  glLightfv(GL_LIGHT0, GL_POSITION, lightPosition);
  glLightfv(GL_LIGHT0, GL_AMBIENT, ambient);
  glLightfv(GL_LIGHT0, GL_DIFFUSE, diffuse);
  glLightfv(GL_LIGHT0, GL_SPECULAR, specular);
 
  glEnable(GL_LIGHT0);
  glLightModeli(GL_LIGHT_MODEL_LOCAL_VIEWER, GL_TRUE);
  glEnable(GL_LIGHTING);
}

void display (void) {
  //code borrowed from Angel pg. 263
  int i;
  GLfloat yl=5;
  GLfloat m[16]; //shadow projection matrix
  for (i=0;i<15;i++) m[i]=0.0;
  m[0]=m[5]=1.0;
  m[10]=1;
  m[7]=-1.0/yl;

  glClearColor(1,1,1,1);   // clear screen to white
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  twCamera(); // sets up camera based on bounding box coords.
  twTriple lightGray = {0.7, 0.7, 0.7};
  twColor(lightGray,0,0);
  glBegin(GL_POLYGON);
  glVertex3f(-10,10,5);
  glVertex3f(10,10,6);
  glVertex3f(0,10,-3);
  glEnd();
  glMatrixMode(GL_MODELVIEW);
  glPushMatrix();
  glTranslatef(-12,20,-2);
  twColorName(TW_YELLOW);
  glutSolidSphere(1,10,10);
  glMultMatrixf(m);
  glTranslatef(12,-20,2);
  twColorName(TW_RED);                //original object
  glBegin(GL_POLYGON);
  glVertex3f(-10,10,5);
  glVertex3f(10,10,6);
  glVertex3f(0,10,-3);
  glEnd();
  glPopMatrix();

  glTranslatef(-10,0,0);
  twTriple gray = {0.6, 0.6, 0.6};
  twColor(gray,0,0);        // shadow color
  glutSolidTorus(2,5,20,20);
  glMatrixMode(GL_MODELVIEW);
  glPushMatrix();
  // glTranslatef(-12,20,-2);
  glTranslatef(12,-20,2);
  twColorName(TW_BLUE);
  glutSolidSphere(1,10,10);
  glMultMatrixf(m);
  //glTranslatef(12,-20,2);
  glTranslatef(-12,20,-2);
  twColorName(TW_GREEN);
  glutSolidTorus(2,5,20,20);
  glPopMatrix();
  
  glFlush();
  glutSwapBuffers();       // necessary for animation
}

  


/*void display(void) {
  //this code is borrowed from Angel pg. 263
  int i;
  GLfloat a=0;
  GLfloat b=-7;
  GLfloat c=0;
  GLfloat d=-2;
  GLfloat m[16];  // shadow projection matrix
   for (i=0;i<15;i++) m[i]=0.0;
  m[0]=m[5]=m[10]=-d;
  m[3]=a;
  m[7]=b;
  m[11]=c;

  glClearColor(1,1,1,1);   // clear screen to white
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  twCamera(); // sets up camera based on bounding box coords.
  glPushMatrix();
  glPushAttrib(GL_LIGHTING_BIT);
  twColor(0.7,0.7,0.7,70);

  glPopMatrix();
  
  glMatrixMode(GL_MODELVIEW);
  glPushMatrix();
  glTranslatef(a,b,c);
  glMultMatrixf(m);
  glTranslatef(-a,-b,-c);
  glDisable(GL_LIGHTING);
  twColor(0.7,0.7,0.7,10);
  glutSolidTeapot(10);
  glPopAttrib();
  glPopMatrix();

  glEnable(GL_LIGHTING);
  glFlush();
  glutSwapBuffers();       // necessary for animation
}
*/

int main(int argc, char** argv) {
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
  twInitWindowSize(500,500);
  glutCreateWindow(argv[0]);
  twBoundingBox(-20,20,-20,20,-20,20); // calculate near and far 
  glutDisplayFunc(display);
  twMainInit();
//lighting();
  glutMainLoop();
  return 0;
}