Thread: 3D ball problem

I'm trying to swing two balls so that when the first ball swings from -20 degrees to zero it stops and sends the second ball swinging out to 20 degrees and returning back to zero again.

However, that problem is that whilst I can get both balls swinging between the ranges at the same time I can't get the one ball to move whilst the second is still and vice versa. I tried a switch case but that failed totally.

any ideas?
then I can get a Newton's Cradle working

Code:

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

using namespace std;
HDC hdc;

int slices = 40;
	int stacks = 40;
	float radius = 0.1;

float angle[2] = {0.0f, 0.0f};



GLfloat mat_ambient[] = {0.5, 0.5, 0.5, 0.01};
GLfloat mat_specular[] = {0.1, 0.1, 0.1, 0.01};
GLfloat mat_shininess[] = {50.0};
GLfloat light_position[] = {10.0, 10.0, 20.0, 0.0};
GLfloat model_ambient[] = {0.5, 0.5, 0.5, 0.0};

void setupMaterials() {
	glMaterialfv(GL_FRONT, GL_AMBIENT, mat_ambient);
	glMaterialfv(GL_FRONT, GL_SPECULAR, mat_specular);
	glMaterialfv(GL_FRONT, GL_SHININESS, mat_shininess);
	glLightfv(GL_LIGHT0, GL_POSITION, light_position);
	glLightModelfv(GL_LIGHT_MODEL_AMBIENT, model_ambient);
}

void changeColour(GLfloat r, GLfloat g, GLfloat b, GLfloat A) {
	model_ambient[0] = r;
	model_ambient[1] = g;
	model_ambient[2] = b;
	model_ambient[3] = A;
	glLightModelfv(GL_LIGHT_MODEL_AMBIENT, model_ambient);
}

void init(void) {
	glClearColor(0.0, 0.0, 0.0, 0.01);
	setupMaterials();
	glEnable(GL_LIGHTING);
	glEnable(GL_LIGHT0);
	glEnable(GL_DEPTH_TEST);
	glEnable(GL_CULL_FACE);
	glFrontFace(GL_CCW);
	glShadeModel(GL_SMOOTH);
}

void reshape(int w, int h) {
	GLfloat fAspect;
	if(h==0) h=1;

	glViewport(0,0,w,h);

	fAspect = (GLfloat)w / (GLfloat)h;

	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();

	gluPerspective(60, fAspect, 0.5, 1000.0);
	glTranslatef(0,0,-1);
	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();
}
void DrawSphere(){

glPushMatrix();


  changeColour(0.3, 0.3, 0.35, 0.0);
        glTranslatef(0.0f, 0.5f,0.0f);
        glBegin(GL_LINES);

        glVertex2f(0.0, 0.0);
        glVertex2f(0.0, -0.5);
        glEnd();

        glTranslatef(0.0, -0.5, 0.0);
        glutSolidSphere(radius, slices, stacks);


    glPopMatrix();
}
void DrawSphere2(){

glPushMatrix();
  changeColour(0.3, 0.3, 0.35, 0.0);
        glTranslatef(0.0f,0.5f,0.0f);
        glBegin(GL_LINES);

        glVertex2f(0.2, 0.0);
        glVertex2f(0.2, -0.5);
        glEnd();
    glTranslatef(0.2, -0.5, 0.0);

        glutSolidSphere(radius, slices, stacks);


    glPopMatrix();
}
void display(void) {

bool static sphere= false;
    bool static sphere2=true;
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);



if (sphere){
    angle[0] = angle[0] +1.0f;
}
else {
    angle[0] = angle[0] -1.0f;
}
if (sphere2){
    angle[1] = angle[1] +1.0f;
}
else {
    angle[1] = angle[1] -1.0f;
}

    if(angle[0]<=-20.0f){
    sphere = true;

    }

if(angle[0]>=0.0f){
    sphere = false;

}
glPushMatrix();
    glTranslatef(0.0, 0.5,0.0);
    glRotatef(angle[0],0.0,0.0,1.0);
    glTranslatef(-0.0, -0.5, 0.0);
   DrawSphere();
   glPopMatrix();

 if(angle[1]<=0.0f){
    sphere2 = true;
    }

if(angle[1]>=20.0f){
    sphere2 = false;
}
   glPushMatrix();
   glTranslatef(0.2, 0.5,0.0);
    glRotatef(angle[1],0.0,0.0,1.0);
    glTranslatef(-0.2,-0.5,0.0);
   DrawSphere2();

  glPopMatrix();

    glutSwapBuffers();
}


void keyboard(unsigned char key, int x, int y) {
	switch (key) {
		case 27:
			exit(0); // Exit the application if 'Esc' key is pressed
	}
}

void animate() {
    Sleep(100);

    glutPostRedisplay();
}
void processMouse(int button, int state, int x, int y){
if (state==GLUT_DOWN){
if((button==GLUT_LEFT_BUTTON) && x<350 && x>450){
glTranslatef(0.0, 0.5,0.0);
glRotatef(x, 0.0 ,0.0, 1.0);
glTranslatef(0.0, -0.5,0.0);
angle[0] = angle[0]+x;
}
}
if (state==GLUT_UP){
if (button==GLUT_LEFT_BUTTON && angle[0]!=0){
animate();
}
}
}
int main(int argc, char * argv[]) {
    glutInit(&argc, argv);
    glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
    glutInitWindowSize (800, 600);
    glutCreateWindow (argv[0]);   init();
    glutKeyboardFunc (keyboard);
    PaintDesktop(hdc);
    glCullFace(GL_BACK);
    glutDisplayFunc (display);
    glutReshapeFunc (reshape);
    glutMouseFunc(processMouse);
    glutIdleFunc(animate);
    glutMainLoop();
    return 0;
}