prog4-cube_perspective.c

// 4. Draw a color cube and allow the user to move the camera suitably to experiment with perspective viewing.

/*
ALGORITHM
1. Initialize vertices, normals and colors of the color cube. Also initialize theta, axis and viewer position.
2. Define main()
		- Enable display mode as double and depth buffer.
		- Register mouse and keyboard callback function.
		- Enable depth test.
3. Define reshape(). Enable either glFrustum or gluPerspective for perspective viewing.
4. Define mouse callback mouse()
		- Program for left, middle and right buttons for x, y and z axis respectively.
		- Increment theta for every click.
		- Reinitialize theta, If theta > 360 then theta = 0
		- Call display()
5. Define keyboard callback keys()
		Program for moving the viewer towards or away from the object by incrementing or decrementing by 1,
		for x, y & z keys for respective directions accordingly.
6. Define callback function display()
		- Load identity matrix and gluLookAt for viewer.
		- Define rotation function for x, y & z axis.
		- Draw the colorcube using righthand rule.
		- Swap buffers for there is animation in the scene.
*/

#include <stdlib.h>
#include <GL/glut.h>

	GLfloat vertices[][3] = {{-1.0,-1.0,-1.0},{1.0,-1.0,-1.0},
	{1.0,1.0,-1.0}, {-1.0,1.0,-1.0}, {-1.0,-1.0,1.0},
	{1.0,-1.0,1.0}, {1.0,1.0,1.0}, {-1.0,1.0,1.0}};

	GLfloat normals[][3] = {{-1.0,-1.0,-1.0},{1.0,-1.0,-1.0},
	{1.0,1.0,-1.0}, {-1.0,1.0,-1.0}, {-1.0,-1.0,1.0},
	{1.0,-1.0,1.0}, {1.0,1.0,1.0}, {-1.0,1.0,1.0}};

	GLfloat colors[][3] = {{0.0,0.0,0.0},{1.0,0.0,0.0},
	{1.0,1.0,0.0}, {0.0,1.0,0.0}, {0.0,0.0,1.0},
	{1.0,0.0,1.0}, {1.0,1.0,1.0}, {0.0,1.0,1.0}};

void polygon(int a, int b, int c , int d)
{
	glBegin(GL_POLYGON);
		glColor3fv(colors[a]);
		glNormal3fv(normals[a]);
		glVertex3fv(vertices[a]);
		glColor3fv(colors[b]);
		glNormal3fv(normals[b]);
		glVertex3fv(vertices[b]);
		glColor3fv(colors[c]);
		glNormal3fv(normals[c]);
		glVertex3fv(vertices[c]);
		glColor3fv(colors[d]);
		glNormal3fv(normals[d]);
		glVertex3fv(vertices[d]);
	glEnd();
}


void colorcube()
{
	polygon(0,3,2,1);
	polygon(2,3,7,6);
	polygon(0,4,7,3);
	polygon(1,2,6,5);
	polygon(4,5,6,7);
	polygon(0,1,5,4);
}

static GLfloat theta[] = {0.0,0.0,0.0};
static GLint axis = 2;
static GLdouble viewer[]= {0.0, 0.0, 5.0}; /* initial viewer location */

void display(void)
{

 glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

/* Update viewer position in modelview matrix */

	glLoadIdentity();
	gluLookAt(viewer[0],viewer[1],viewer[2], 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);

/* rotate cube */

	glRotatef(theta[0], 1.0, 0.0, 0.0);
	glRotatef(theta[1], 0.0, 1.0, 0.0);
	glRotatef(theta[2], 0.0, 0.0, 1.0);

 colorcube();

 glFlush();
	glutSwapBuffers();
}

void mouse(int btn, int state, int x, int y)
{
	if(btn==GLUT_LEFT_BUTTON && state == GLUT_DOWN) axis = 0;
	if(btn==GLUT_MIDDLE_BUTTON && state == GLUT_DOWN) axis = 1;
	if(btn==GLUT_RIGHT_BUTTON && state == GLUT_DOWN) axis = 2;
	theta[axis] += 2.0;
	if( theta[axis] > 360.0 ) theta[axis] -= 360.0;
	display();
}

void keys(unsigned char key, int x, int y)
{
/* Use x, X, y, Y, z, and Z keys to move viewer */

   if(key == 'x') viewer[0]-= 1.0;
   if(key == 'X') viewer[0]+= 1.0;
   if(key == 'y') viewer[1]-= 1.0;
   if(key == 'Y') viewer[1]+= 1.0;
   if(key == 'z') viewer[2]-= 1.0;
   if(key == 'Z') viewer[2]+= 1.0;
   display();
}

void myReshape(int w, int h)
{
 glViewport(0, 0, w, h);

/* Use a perspective view */

 glMatrixMode(GL_PROJECTION);
 glLoadIdentity();
	if(w<=h) glFrustum(-2.0, 2.0, -2.0 * (GLfloat) h/ (GLfloat) w,
       2.0* (GLfloat) h / (GLfloat) w, 2.0, 20.0);
	else glFrustum(-2.0, 2.0, -2.0 * (GLfloat) w/ (GLfloat) h,
       2.0* (GLfloat) w / (GLfloat) h, 2.0, 20.0);

 glMatrixMode(GL_MODELVIEW);
}

int  main(int argc, char **argv)
{
 glutInit(&argc, argv);
 glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
 glutInitWindowSize(500, 500);
 glutCreateWindow("Colorcube Viewer");
 glutReshapeFunc(myReshape);
 glutDisplayFunc(display);
	 glutMouseFunc(mouse);
	 glutKeyboardFunc(keys);
	 glEnable(GL_DEPTH_TEST);
 	 glutMainLoop();
 return 0;
}