/* robot.c    */

/* E. Angel, Interactive Computer Graphics */
/* A Top-Down Approach with OpenGL, Third Edition */
/* Addison-Wesley Longman, 2003 */
/* 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 */#include <GL/glut.h>/* Let's start using #defines so we can betterinterpret 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 0.5typedef 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 matrixto its state before functions were entered and userotation, translation, and scaling to create instancesof 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 */}voidmain(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();}