/* robot.c                                                            */
/* Robot program (Chapter 9). Cylinder for base, scaled cube for arms */
/* Shows use of instance transformation to define parts (symbols)     */
/* The cylinder is a quadric object from the GLU library              */
/* The cube is also obtained from GLU                                 */
/* E. Angel, Interactive Computer Graphics                            */

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

/* Let's start using #defines so we can better
interpret the constants (and change them) */

#define BASE_HEIGHT 2.0
#define BASE_RADIUS 1.0
#define LOWER_ARM_HEIGHT 5.0
#define LOWER_ARM_WIDTH 0.5
#define UPPER_ARM_HEIGHT 5.0
#define UPPER_ARM_WIDTH 0.5

typedef float point[3];

static GLfloat theta[] = {0.0,0.0,0.0};
static GLint axis = 0;
GLUquadricObj  *p; /* pointer to quadric object */

/* Define the three parts */
/* Note use of push/pop to return modelview matrix
to its state before functions were entered and use
rotation, translation, and scaling to create instances
of symbols (cube and cylinder */

void base()
{
  glPushMatrix();
  /* rotate cylinder to align with y axis */
  glRotatef(-90.0, 1.0, 0.0, 0.0);

  /* cyliner aligned with z axis, render with
  5 slices for base and 5 along length */
  gluCylinder(p, BASE_RADIUS, BASE_RADIUS, BASE_HEIGHT, 5, 5);
  glPopMatrix();
}

void upper_arm()
{
  glPushMatrix();
  glTranslatef(0.0, 0.5*UPPER_ARM_HEIGHT, 0.0);
  glScalef(UPPER_ARM_WIDTH, UPPER_ARM_HEIGHT, UPPER_ARM_WIDTH);
  glutWireCube(1.0);
  glPopMatrix();
}

void lower_arm()
{
  glPushMatrix();
  glTranslatef(0.0, 0.5*LOWER_ARM_HEIGHT, 0.0);
  glScalef(LOWER_ARM_WIDTH, LOWER_ARM_HEIGHT, LOWER_ARM_WIDTH);
  glutWireCube(1.0);
  glPopMatrix();
}

void display(void)
{
  /* Accumulate ModelView Matrix as we traverse tree */
  glClear(GL_COLOR_BUFFER_BIT);
  glLoadIdentity();
  glColor3f(1.0, 0.0, 0.0);
  glRotatef(theta[0], 0.0, 1.0, 0.0);
  base();
  glTranslatef(0.0, BASE_HEIGHT, 0.0);
  glRotatef(theta[1], 0.0, 0.0, 1.0);
  lower_arm();
  glTranslatef(0.0, LOWER_ARM_HEIGHT, 0.0);
  glRotatef(theta[2], 0.0, 0.0, 1.0);
  upper_arm();
  glFlush();
  glutSwapBuffers();
}

void mouse(int btn, int state, int x, int y)
{
  /* left button increase joint angle, right button decreases it */
  if(btn==GLUT_LEFT_BUTTON && state == GLUT_DOWN) 
  {
    theta[axis] += 5.0;
    if( theta[axis] > 360.0 ) theta[axis] -= 360.0;
  }
  if(btn==GLUT_RIGHT_BUTTON && state == GLUT_DOWN) 
  {
    theta[axis] -= 5.0;
    if( theta[axis] < 360.0 ) theta[axis] += 360.0;
  }
  display();
}

void menu(int id)
{
  /* menu selects which angle to change or whether to quit */
  if(id == 1 ) axis=0;
  if(id == 2) axis=1;
  if(id == 3 ) axis=2;
  if(id ==4 ) exit(0);
}

void myReshape(int w, int h)
{
  glViewport(0, 0, w, h);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  if (w <= h)
    glOrtho(-10.0, 10.0, -5.0 * (GLfloat) h / (GLfloat) w,
            15.0 * (GLfloat) h / (GLfloat) w, -10.0, 10.0);
  else
    glOrtho(-10.0 * (GLfloat) w / (GLfloat) h,
            10.0 * (GLfloat) w / (GLfloat) h, -5.0, 15.0, -10.0, 10.0);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
}

void myinit()
{
  glClearColor(1.0, 1.0, 1.0, 1.0);
  glColor3f(1.0, 0.0, 0.0);
  p=gluNewQuadric(); /* allocate quadric object */
  gluQuadricDrawStyle(p, GLU_LINE); /* render it as wireframe */
}

int main(int argc, char *argv[])
{
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
  glutInitWindowSize(500, 500);
  glutCreateWindow("robot");
  myinit();
  glutReshapeFunc(myReshape);
  glutDisplayFunc(display);
  glutMouseFunc(mouse);
  glutCreateMenu(menu);
  glutAddMenuEntry("base", 1);
  glutAddMenuEntry("lower arm", 2);
  glutAddMenuEntry("upper arm", 3);
  glutAddMenuEntry("quit", 4);
  glutAttachMenu(GLUT_MIDDLE_BUTTON);
  glutMainLoop();
  return 0;
}