/* rotating cube demo with trackball*/

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

#define M_PI 3.14159
#define bool int
#define false 0
#define true 1


int  winWidth, winHeight;
float angle = 0.0, axis[3], trans[3];
bool  trackingMouse = false;
bool redrawContinue = false;
bool trackballMove = false;

/* draw the cube */

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 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, int face)
{

   /* draw a polygon via list of vertices */

   glBegin(GL_POLYGON);
     glColor3fv(colors[a]);
     glVertex3fv(vertices[a]);
     glVertex3fv(vertices[b]);
     glVertex3fv(vertices[c]);
     glVertex3fv(vertices[d]);
   glEnd();
}

void colorcube()
{

    /* map vertices to faces */

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

/* These functions implement a simple trackball-like motion
control */

float lastPos[3] = {0.0F, 0.0F, 0.0F};
int curx, cury;
int startX, startY;

void trackball_ptov(int x, int y, int width, int height, float v[3])
{
    float d, a;

    /* project x,y onto a hemisphere centered within width, height */
    v[0] = (2.0F*x - width) / width;
    v[1] = (height - 2.0F*y) / height;
    d = (float) sqrt(v[0]*v[0] + v[1]*v[1]);
    v[2] = (float) cos((M_PI/2.0F) * ((d < 1.0F) ? d : 1.0F));
    a = 1.0F / (float) sqrt(v[0]*v[0] + v[1]*v[1] + v[2]*v[2]);
    v[0] *= a;
    v[1] *= a;
    v[2] *= a;
}


void mouseMotion(int x, int y)
{
    float curPos[3], dx, dy, dz;

    trackball_ptov(x, y, winWidth, winHeight, curPos);
  if(trackingMouse)
  {
    dx = curPos[0] - lastPos[0];
    dy = curPos[1] - lastPos[1];
    dz = curPos[2] - lastPos[2];

    if (dx || dy || dz)
    {
    angle = 90.0F * sqrt(dx*dx + dy*dy + dz*dz);

    axis[0] = lastPos[1]*curPos[2] - lastPos[2]*curPos[1];
    axis[1] = lastPos[2]*curPos[0] - lastPos[0]*curPos[2];
    axis[2] = lastPos[0]*curPos[1] - lastPos[1]*curPos[0];

    lastPos[0] = curPos[0];
    lastPos[1] = curPos[1];
    lastPos[2] = curPos[2];
    }
  }

    glutPostRedisplay();
}

void startMotion(int x, int y)
{

    trackingMouse = true;
    redrawContinue = false;
    startX = x; startY = y;
    curx = x; cury = y;
    trackball_ptov(x, y, winWidth, winHeight, lastPos);
    trackballMove=true;
}

void stopMotion(int x, int y)
{

    trackingMouse = false;

    if (startX != x || startY != y)
    {
    redrawContinue = true;
       } else
       {
    angle = 0.0F;
    redrawContinue = false;
    trackballMove = false;
       }
}

void display()
{
    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);

    /* view transform */

    if (trackballMove)
    {
     glRotatef(angle, axis[0], axis[1], axis[2]);

    }
 colorcube();
    glutSwapBuffers();
}


void mouseButton(int button, int state, int x, int y)
{
 if(button==GLUT_RIGHT_BUTTON) exit(0);
 if(button==GLUT_LEFT_BUTTON) switch(state)
 {
    case GLUT_DOWN:
    y=winHeight-y;
    startMotion( x,y);
    break;
    case GLUT_UP:
    stopMotion( x,y);
    break;
       }
}

void myReshape(int w, int h)
{
    glViewport(0, 0, w, h);
    winWidth = w;
    winHeight = h;
}

void spinCube()
{
    if (redrawContinue) glutPostRedisplay();
}

int main(int argc, char **argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
    glutInitWindowSize(500, 500);
    glutCreateWindow("colorcube");
    glutReshapeFunc(myReshape);
    glutDisplayFunc(display);
    glutIdleFunc(spinCube);
    glutMouseFunc(mouseButton);
    glutMotionFunc(mouseMotion);
    glEnable(GL_DEPTH_TEST);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(-2.0, 2.0, -2.0, 2.0, -2.0, 2.0);
    glMatrixMode(GL_MODELVIEW);
    glutMainLoop();
}
