//example robot program
//www.timestocome.com


//to compile under mac osx gcc -framework OpenGL -framework GLUT -o robot robot.c
#include <GLUT/glut.h>



#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;						



void base(){



	glPushMatrix();

	//rotate to align w/ y axis

	glRotatef(-90.0, 1.0, 0.0, 0.0);		//angle, x, y, z

	//cylinder aligned w/ z axis render w/ 5 slices for base and length

	gluCylinder(p, BASE_RADIUS, BASE_RADIUS, BASE_HEIGHT, 15, 10);//pointer, base radius, top radius, height, slices, stacks

	glPopMatrix();

}



void upper_arm(){



	glPushMatrix();

	glTranslatef(0.0, 0.5*LOWER_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*UPPER_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 increases joint angle, right decreases

	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){

	//select which angle to change or quit

	if(id == 1) axis = 0;
	if(id == 2) axis = 1;
	if(id == 3) axis = 2;
	if(id == 4) axis = 3;

}



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*(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 object
	gluQuadricDrawStyle(p, GLU_LINE);		//wireframe rendering

}



void 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_RIGHT_BUTTON);



		glutMainLoop();

}