What is the best way to do range finding around a tower?

archive script-blocks
1

I am trying to do a little tower defense game. If I have a tower who has range of 10 what is the best way to do a collision detection for Enemies 360 degrees around the tower?



Do I do 360 ray traces? or is there a sphere collision or something that I can call?



Thanks,

Greg

2

You can use a sphere bounding box with the wanted radius. From this you can check if there’s anything inside and/or intersecting it.

3

You can use a GhostObject to track the overlapping physics objects but you have to use physics collision shapes for that. Else, you can use a sphere geometry and collideWith() the rootNode to check for overlaps. If thats not the solution I guess given the size of your levels it would always be faster simply checking all objects if they are in range than doing complicated checks.

4

I tried this

[java]CollisionResults results = new CollisionResults();

float radius = 2.0f;

Vector3f center = Vector3f.ZERO;

TDApplication.getInstance().getRootNode().collideWith(new BoundingSphere(radius,center ), results);

for(CollisionResult collisionResult : results){

System.out.println("Collision Result" +collisionResult.getGeometry().getName() );

}[/java]

Getting Java Exception

[java]



SEVERE: Uncaught exception thrown in Thread[LWJGL Renderer Thread,5,main]

com.jme3.collision.UnsupportedCollisionException

at com.jme3.bounding.BoundingSphere.collideWith(BoundingSphere.java:807)

at com.jme3.collision.bih.BIHNode.intersectWhere(BIHNode.java:218)

at com.jme3.collision.bih.BIHTree.collideWithBoundingVolume(BIHTree.java:444)

at com.jme3.collision.bih.BIHTree.collideWith(BIHTree.java:457)

at com.jme3.scene.Mesh.collideWith(Mesh.java:846)

at com.jme3.scene.Geometry.collideWith(Geometry.java:338)

at com.jme3.scene.Node.collideWith(Node.java:494)

at com.scriptblocks.td.model.Tower.inRange(Tower.java:44)

at com.scriptblocks.td.model.Tower.simpleUpdate(Tower.java:29)

at com.scriptblocks.td.TDApplication.simpleUpdate(TDApplication.java:90)

at com.jme3.app.SimpleApplication.update(SimpleApplication.java:255)

at com.jme3.system.lwjgl.LwjglAbstractDisplay.runLoop(LwjglAbstractDisplay.java:144)

at com.jme3.system.lwjgl.LwjglDisplay.runLoop(LwjglDisplay.java:185)

at com.jme3.system.lwjgl.LwjglAbstractDisplay.run(LwjglAbstractDisplay.java:218)

at java.lang.Thread.run(Thread.java:662)

[/java]

5

You have to do spatial.collideWith(BoundingVolume), not the other way round.

Edit: Duh, you did that… Do you have any funny geometries in your scene? Like not created by jme?

6

Nope just Boxes

7

I’m not getting something I suppose but try with a full sphere spatial.

Edit: It could very well be that sphere vs world collisions are not implemented. In that case you’d have to use bullet for collisions. Basically its just attaching a kinematic RigidBodyControl to each box… It will use the most efficient box shape by default if you use normal boxes. Then you can go about using a GhostControl with sphere collision shape for overlaps.

8

Yeah I dont think BoundingSphere has been finished yet. It does a check for instanceof Ray and fails on everything else



i switched to

[java]

CollisionResults results = new CollisionResults();

Vector3f center = this.getWorldTranslation();

TDApplication.getInstance().getRootNode().collideWith(new BoundingBox(center, range,0.1f,range ), results);

[/java]



but

[java] Vector3f pt = collisionResult.getContactPoint();[/java]



pt returns null :frowning:





Thanks for any help.

9

I’m pretty sure that only Rays will work like you want. There is no such thing as one contact point with a bounding box.



You may have to do your own sphere->sphere calculations as a “broad phase” and then use ray intersections for things that collide in the broad phase.

10

When you check collision against box/sphere, it checks it for every triangle

11

You can just do a Vector3f.length() calculation between the two nodes…



e.g. if( Tower.myNode.getWorldLocation().subtract(Enemy.myNode.getWorldLocation()).length() < 10 ) Tower.Fire(Enemy);