/* prac5a.c  */

/* 
	Purpose:	This program constructs a house, and uses function keys
				to control the projection transfomations. 
*/


#ifdef __APPLE__
#include <GLUT/glut.h>
#else
#include <GL/glut.h>
#endif

#include <stdlib.h>
#include <stdio.h>

#define KEY_ESC 27      /* glut doesn't define this one */


/* Global Definitions */
static const float mV0[3] = {0.0,0.0,0.0};
static const float mV1[3] = {1.0,0.0,0.0};
static const float mV2[3] = {1.0,1.0,0.0};
static const float mV3[3] = {0.0,1.0,0.0};
static const float mV4[3] = {0.0,0.0,1.0};
static const float mV5[3] = {1.0,0.0,1.0};
static const float mV6[3] = {1.0,1.0,1.0};
static const float mV7[3] = {0.0,1.0,1.0};
static const float mV8[3] = {0.5,1.25,0.0};
static const float mV9[3] = {0.5,1.25,1.0};


void printHelp( void )
{

	fprintf(stdout, 
		"\nHouse\n\n"
                "Escape key - exit the program\n\n"
		"F2  - 2D orthographic projection\n"
		"F3  - 3D orthographic projection\n"
		"F4  - 3D perspective projection\n"
		"F5  - rotate model\n");

}

GLvoid keyboard( GLubyte key, GLint x, GLint y)
{
    switch (key) 
	{
		case KEY_ESC:   /* exit when escape key is pressed */
			exit(0);
    }
}


GLvoid specialkeys( GLint key, GLint x, GLint y)
{
    switch (key) 
    {

	case GLUT_KEY_F1:   /* print Help information */
	    printHelp ( );
    break;

	case GLUT_KEY_F2:   /* 2D orthographic projection */
		glMatrixMode(GL_PROJECTION);
		glLoadIdentity();
		gluOrtho2D(-2.0, 2.0, -2.0, 2.0);
		/* Note that this is equivalent to glOrtho(-2,2,-2,2,-1,1);  */
		glMatrixMode(GL_MODELVIEW);
		glLoadIdentity();
	break;

	case GLUT_KEY_F3:   /* 3D orthographic projection*/
		glMatrixMode(GL_PROJECTION);
		glLoadIdentity();
		glOrtho(-2.0, 2.0, -2.0, 2.0, -2.0, 2.0);
		glMatrixMode(GL_MODELVIEW);
		glLoadIdentity();
	break;

	case GLUT_KEY_F4:   /* Perspective projection*/
		glMatrixMode(GL_PROJECTION);
		glLoadIdentity();
		gluPerspective(50, 1.0, 1.0, 8.0);
		glMatrixMode(GL_MODELVIEW);
		glLoadIdentity();
		glTranslatef(0.0, 0.0, -4.0);
	break;

	case GLUT_KEY_F5:   /* Rotate*/
		glRotatef(30.0, 0, 1, 0);
	break;
    }
	glutPostRedisplay();
}

GLvoid checkError( const char* const label )
{
	GLenum error;

	error = glGetError();
	while ( GL_NO_ERROR != error )
	{
		fprintf( stderr,"%s: %s\n", label, gluErrorString(error) );
		error = glGetError();
	}
}

GLvoid drawHouse( GLvoid )
{
	/* draw rear of house */
	glBegin(GL_LINE_LOOP);
	  glVertex3fv(mV0);
	  glVertex3fv(mV1);
	  glVertex3fv(mV2);
	  glVertex3fv(mV3);
	glEnd();

	/* draw front of house */
	glBegin(GL_LINE_LOOP);
	  glVertex3fv(mV4);
	  glVertex3fv(mV5);
	  glVertex3fv(mV6);
	  glVertex3fv(mV7);
	glEnd();

	/* draw roof gable at rear and front of house, and connect the two pieces */
	glBegin(GL_LINES);
	  glVertex3fv(mV2);
	  glVertex3fv(mV8);
	  glVertex3fv(mV8);
	  glVertex3fv(mV3);
	  glVertex3fv(mV6);
	  glVertex3fv(mV9);
	  glVertex3fv(mV9);
	  glVertex3fv(mV7);
	  glVertex3fv(mV8);
	  glVertex3fv(mV9);

	  /* join front frame to back frame (the sides of the house) */
	  glVertex3fv(mV0);
	  glVertex3fv(mV4);
	  glVertex3fv(mV1);
	  glVertex3fv(mV5);
	  glVertex3fv(mV3);
	  glVertex3fv(mV7);
	  glVertex3fv(mV2);
	  glVertex3fv(mV6);
	glEnd();
}

GLvoid init( GLvoid )
{
    glClearColor( 1.0, 1.0, 1.0, 1.0);
    glColor3f(1.0,0.0,0.0);
	glLineWidth(1.0);

	/* Initially do a 2D orthographic projection */
	glMatrixMode(GL_PROJECTION);
	gluOrtho2D(-2.0, 2.0, -2.0, 2.0);
	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();
}


GLvoid display( GLvoid )
{
	glClear( GL_COLOR_BUFFER_BIT );

	/* Do all your OpenGL rendering here */

	/* Note that we have deliberately NOT set the modelview matrix to the identity.
		This allows rotations by pressing F5 to build up. In general, this
		is _bad_ programming practice.  */

	drawHouse();

	checkError( "display" );

	glFlush();
}


int main( int argc, char *argv[] )
{
	glutInit( &argc, argv );

	glutInitDisplayMode( GLUT_SINGLE | GLUT_RGB );
	glutCreateWindow( argv[0] );

	init();

    glutKeyboardFunc( keyboard );
    glutSpecialFunc( specialkeys );
	glutDisplayFunc( display ); 

	printHelp( );

	glutMainLoop();

	return 0;
}