3D Programming Tricks - Beginning Android Games - page 575

Listing 11-15. Excerpt from OverlapTester.java; Adding Sphere-Testing Methods
public static boolean overlapSpheres(Sphere s1, Sphere s2) {
float distance = s1.center.distSquared(s2.center);
float radiusSum = s1.radius + s2.radius;
return distance <= radiusSum * radiusSum;
}
public static boolean pointInSphere(Sphere c, Vector3 p) {
return c.center.distSquared(p) < c.radius * c.radius;
}
public static boolean pointInSphere(Sphere c, float x, float y, float z) {
return c.center.distSquared(x, y, z) < c.radius * c.radius;
}
That's again exactly the same code as in the case of circle overlap testing. We just use the
center of the spheres, which are a Vector3 instances instead of a Vector2 instances, as in the
case of a circle.
Note Entire topics have been filled on the topic of 3D collision detection. If you want to dive deep into
that rather interesting world, we suggest the topic Real-Time Collision Detection , by Christer Ericson
(Morgan Kaufmann, 2005). It should be on the shelf of any self-respecting game developer!
GameObject3D and DynamicGameObject3D
Now that we have a nice bounding shape for our 3D objects, we can easily write the equivalent
of the GameObject and DynamicGameObject classes we used in 2D. We just replace any Vector2
instance with a Vector3 instance and use the Sphere class instead of the Rectangle class.
Listing 11-16 shows the GameObject3D class.
Listing 11-16. GameObject3D.java, Representing a Simple Object with a Position and Bounds
package com.badlogic.androidgames.framework;
import com.badlogic.androidgames.framework.math.Sphere;
import com.badlogic.androidgames.framework.math.Vector3;
public class GameObject3D {
public final Vector3 position;
public final Sphere bounds;
public GameObject3D( float x, float y, float z, float radius) {
this .position = new Vector3(x,y,z);
this .bounds = new Sphere(x, y, z, radius);
}
}