Bullet Physics - Learning LibGDX Game Development - page 436

The buttons are simply sprites that on selection will be ticked with a green tick mark.
The InputAdapter interface processes the touch input from the user. The touchup()
function in InputAdapter will check whether the current touch is inside any button.
If the user selects any button, then the button is set, or the program will continue
with the throw/raypicking functions.
To throw the physics object, the applyCentralImpulse() function is called. The
object is thrown at the direction cast by the ray.
The following is the code for ray picking:
Ray ray = cam.getPickRay(screenX, screenY);
Vector3 position = ray.origin.cpy();
rayFrom.set(ray.origin);
rayTo.set(ray.direction).scl(50f).add(rayFrom); // 50 meters
max
rayTestCB.setCollisionObject(null);
rayTestCB.setClosestHitFraction(1f);
worldInstance.getWorld().rayTest(rayFrom, rayTo, rayTestCB);
if (rayTestCB.hasHit()) {
final btCollisionObject obj =
rayTestCB.getCollisionObject();
/**
Do something
*/
}
Here, a ray is created from the input coordinates by the getPickRay() function.
The rayFrom value, a Vector3 value, is set to the origin of the ray, whereas rayTo
is set at a distance of 50 units from the origin point in the ray direction. The callback
object, rayTestCB , is cleared by setting null to the setCollisionObject() function.
Finally, by calling rayTest() , we check whether the ray has hit any object within the
rayFrom and rayTo points.
Finally, dispose everything as shown here:
@Override
public void dispose() {
for (UserData data : UserData.data) {
data.dispose();
}
worldInstance.dispose();