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Solution to Assignment 5, Problem 2
/*
CSCI 384 Assign 5.
Problem 2--shadow of a pyramid.
*/
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <GL/glut.h>
#define PI 3.14159
GLfloat spin= 0.0;
GLfloat m[16]; /*Shadow projection matrix*/
GLfloat xLight = 0.0, zLight = 0.0, yLight = 250.0;
void myinit(void)
{
glClearColor(1.0, 1.0, 1.0, 1.0);
glColor3f(1.0, 0.0, 0.0);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(-250, 250, -250, 250, -250, 250); /*Note, not ortho2D*/
glMatrixMode(GL_MODELVIEW);
}
/*Set up shadow projection matrix*/
void initShadowMatrix(void){
int i;
for (i = 0; i < 16; i++){
m[i] = 0.0;
}
m[0] = m[5] = m[10] = 1.0;
m[7] = -1.0/yLight;
}
void display(void){
/*Note 3D points here. Set up array of 3D vertices*/
typedef GLfloat point3[3];
point3 vertices[5] = { {0.0, 0.0, 100.0}, {100.0, 0.0, 0.0},
{0.0, 100.0, 0.0}, {-100.0, 0.0, 0.0},
{0.0, 0.0, -100.0} };
int i;
/*Note use of Depth buffer bit for hidden surface removal*/
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
/*Draw regular pyramid*/
glLoadIdentity();
glRotatef(30.0, 1.0, 0.0, 0.0); /*Rotate a bit so can see x-z plane*/
glTranslatef(0.0, 100.0, 0.0);
glRotatef(spin, 0.0, 1.0, 0.0); /*Rotate pyramid*/
glScalef(0.75, 0.75, 0.75);
/*Draw pyramid*/
glBegin(GL_TRIANGLES);
glColor3f(1.0, 0.0, 0.0);
for (i=0; i<3; i++){
glVertex3fv(vertices[i]);
}
glColor3f(0.0, 1.0, 0.0);
glVertex3fv(vertices[0]);
glVertex3fv(vertices[2]);
glVertex3fv(vertices[3]);
glColor3f(0.0, 0.0, 1.0);
glVertex3fv(vertices[3]);
glVertex3fv(vertices[2]);
glVertex3fv(vertices[4]);
glColor3f(1.0, 0.0, 1.0);
glVertex3fv(vertices[4]);
glVertex3fv(vertices[2]);
glVertex3fv(vertices[1]);
glEnd();
glBegin(GL_QUADS);
glColor3f(1.0, 1.0, 0.0);
glVertex3fv(vertices[0]);
glVertex3fv(vertices[3]);
glVertex3fv(vertices[4]);
glVertex3fv(vertices[1]);
glEnd();
glPushMatrix(); /*Save current state*/
/*Draw shadow*/
glLoadIdentity();
glRotatef(30.0, 1.0, 0.0, 0.0);
glTranslatef(xLight, yLight, zLight); /*Translate back*/
glMultMatrixf(m); /*Multiply by shadow projection matrix*/
glTranslatef(-xLight, -yLight, -zLight); /*Translate so lightsource is at origin*/
glTranslatef(0.0, 100.0, 0.0);
glRotatef(spin, 0.0, 1.0, 0.0); /*Rotate pyramid*/
glScalef(0.75, 0.75, 0.75);
glColor3f(0.3, 0.3, 0.3);
/*Draw shadow pyramid*/
glBegin(GL_TRIANGLES);
for (i=0; i<3; i++){
glVertex3fv(vertices[i]);
}
glVertex3fv(vertices[0]);
glVertex3fv(vertices[2]);
glVertex3fv(vertices[3]);
glVertex3fv(vertices[3]);
glVertex3fv(vertices[2]);
glVertex3fv(vertices[4]);
glVertex3fv(vertices[4]);
glVertex3fv(vertices[2]);
glVertex3fv(vertices[1]);
glEnd();
glBegin(GL_QUADS);
/*Bottom of pyramid*/
glVertex3fv(vertices[0]);
glVertex3fv(vertices[3]);
glVertex3fv(vertices[4]);
glVertex3fv(vertices[1]);
glEnd();
glPopMatrix();
glFlush();
glutSwapBuffers(); /*Display next buffer*/
}
void idle(void){
spin += 2.0;
if (spin > 360.0)
spin = spin - 360.0;
glutPostRedisplay();
}
int main(int argc, char** argv)
{
glutInit(&argc, argv);
/*Note the GLUT_DOUBLE and GLUT_DEPTH here*/
glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
myinit();
initShadowMatrix();
glutInitWindowSize(500,500);
glutInitWindowPosition(50,50);
glutCreateWindow("Shadow Pyramid");
glutDisplayFunc(display);
glutKeyboardFunc(keys); /*Keyboard function, spins pyramid*/
glutIdleFunc(idle);
glEnable(GL_DEPTH_TEST); /*For hidden surface removal*/
myinit();
glutMainLoop();
return 0;
}
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Constance Royden--croyden@mathcs.holycross.edu
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