/* 
solid 3D unit cube with one vertex at the origin
*/

#include <stdio.h>
#include <GL/gl.h>
#include <GL/glut.h>

struct point {
	float x;
	float y;
	float z;
	};

void setup_da_viewvol()
{
struct point eye;
struct point view;
struct point up;

glEnable(GL_DEPTH_TEST);

/* specify size and shape of view volume */
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(45.0,1.0,0.1,20.0);

/* specify position for view volume */
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();

eye.x = 2.0; eye.y = 2.0; eye.z = 2.0;
view.x = 0.0; view.y = 0.0; view.z = 0.0;
up.x = 0.0; up.y = 1.0; up.z = 0.0;

gluLookAt(eye.x,eye.y,eye.z,view.x,view.y,view.z,up.x,up.y,up.z);
}

void draw_stuff()
{
int i;
struct point front[4]={{0.0,0.0,1.0},{1.0,0.0,1.0},{1.0,1.0,1.0},{0.0,1.0,1.0}};
struct point back[4]={{0.0,0.0,0.0},{0.0,1.0,0.0},{1.0,1.0,0.0},{1.0,0.0,0.0}};
struct point left[4]={{0.0,0.0,0.0},{0.0,0.0,1.0},{0.0,1.0,1.0},{0.0,1.0,0.0}};
struct point right[4]={{1.0,0.0,0.0},{1.0,1.0,0.0},{1.0,1.0,1.0},{1.0,0.0,1.0}};
struct point top[4]={{0.0,1.0,0.0},{0.0,1.0,1.0},{1.0,1.0,1.0},{1.0,1.0,0.0}};
struct point bottom[4]={{0.0,0.0,0.0},{0.0,0.0,1.0},{1.0,0.0,1.0},{1.0,0.0,0.0}};

/* gray background */
glClearColor(0.35,0.35,0.35,0.0);
glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);

glBegin(GL_QUADS); 
glNormal3f(0.0,0.0,1.0);
for(i=0;i<4;i++) glVertex3f(front[i].x,front[i].y,front[i].z);
glNormal3f(0.0,0.0,-1.0);
for(i=0;i<4;i++) glVertex3f(back[i].x,back[i].y,back[i].z);
glNormal3f(-1.0,0.0,0.0);
for(i=0;i<4;i++) glVertex3f(left[i].x,left[i].y,left[i].z);
glNormal3f(1.0,0.0,0.0);
for(i=0;i<4;i++) glVertex3f(right[i].x,right[i].y,right[i].z);
glNormal3f(0.0,1.0,0.0);
for(i=0;i<4;i++) glVertex3f(top[i].x,top[i].y,top[i].z);
glNormal3f(0.0,-1.0,0.0);
for(i=0;i<4;i++) glVertex3f(bottom[i].x,bottom[i].y,bottom[i].z);
glEnd();
}

void do_lights()
{
/* white light */
float light0_ambient[] = { 0.0, 0.0, 0.0, 0.0 };
float light0_diffuse[] = { 1.0, 1.0, 1.0, 0.0 };
float light0_specular[] = { 1.0, 1.0, 1.0, 0.0 };
float light0_position[] = { 1.5, 2.0, 2.0, 1.0 };
float light0_direction[] = { -1.5, -2.0, -2.0, 1.0};

/* turn off scene default ambient */
glLightModelfv(GL_LIGHT_MODEL_AMBIENT,light0_ambient);

/* make specular correct for spots */
glLightModeli(GL_LIGHT_MODEL_LOCAL_VIEWER,1);

glLightfv(GL_LIGHT0,GL_AMBIENT,light0_ambient);
glLightfv(GL_LIGHT0,GL_DIFFUSE,light0_diffuse);
glLightfv(GL_LIGHT0,GL_SPECULAR,light0_specular);
glLightf(GL_LIGHT0,GL_SPOT_EXPONENT,1.0);
glLightf(GL_LIGHT0,GL_SPOT_CUTOFF,180.0);
glLightf(GL_LIGHT0,GL_CONSTANT_ATTENUATION,0.5);
glLightf(GL_LIGHT0,GL_LINEAR_ATTENUATION,0.1);
glLightf(GL_LIGHT0,GL_QUADRATIC_ATTENUATION,0.01);
glLightfv(GL_LIGHT0,GL_POSITION,light0_position);
glLightfv(GL_LIGHT0,GL_SPOT_DIRECTION,light0_direction);

glEnable(GL_LIGHTING);
glEnable(GL_LIGHT0);
}

void do_material()
{
float mat_ambient[] = {0.0,0.0,0.0,1.0};
float mat_diffuse[] = {0.9,0.9,0.1,1.0};
float mat_specular[] = {1.0,1.0,1.0,1.0};
float mat_shininess[] = {2.0};

glMaterialfv(GL_FRONT,GL_AMBIENT,mat_ambient);
glMaterialfv(GL_FRONT,GL_DIFFUSE,mat_diffuse);
glMaterialfv(GL_FRONT,GL_SPECULAR,mat_specular);
glMaterialfv(GL_FRONT,GL_SHININESS,mat_shininess);
}

void do_stuff()
{
setup_da_viewvol();
do_lights();
do_material();
draw_stuff();
}

int main()
{
glutInitDisplayMode(GLUT_RGBA|GLUT_DEPTH);
glutInitWindowSize(512,512);
glutInitWindowPosition(100,50);
glutCreateWindow("my_cool_cube");
glutDisplayFunc(do_stuff);
glutMainLoop();
return 0;
}