Making a top down isometric shooter, need some help with hit detection

Troubleshooting General Help
1

So, I’m trying to do ray-casting for hit detection in my shooter, but the ray always seems to be off from the coordinates I’m sending it. I cant for the life of me figure out where I’m making an error, other than that it could have something to do with the camera angle.



Below I have pasted in the code for my shoot() method, I’m also drawing a line for testing that should show where the ray is, but the mark that shows up on the targets is always some small angle off from where the line shows.



[java]

private void shoot(){

//BUG: Ray does not line up perfectly with line



CollisionResults results = new CollisionResults();



Vector2f mousePosNoOff = new Vector2f();



//Converts from screen position to a coord grid of -1.0 to +1.0

mousePosNoOff.x = (cursorPos.x - settings.getWidth()/2)/(settings.getWidth()/2);

mousePosNoOff.y = (cursorPos.y - settings.getHeight()/2)/(settings.getHeight()/2);



//Convert to polar coords so I can add 45 degrees

float polarAngle = mousePosNoOff.getAngle() - FastMath.PI/4;

float polarMag = FastMath.sqrt(FastMath.pow(mousePosNoOff.x, 2) + FastMath.pow(mousePosNoOff.y, 2));



Vector2f mousePos = new Vector2f(polarMag * FastMath.cos(polarAngle),

polarMag * FastMath.sin(polarAngle));



Vector3f playerPos = player.getWorldPos();



Vector3f rayCoords = new Vector3f(((mousePos.x * 300) + playerPos.x),

((mousePos.y * 300) + playerPos.y),

1f);



Ray ray = new Ray(playerPos, rayCoords);

System.out.println(ray);



//Line that I’m using for testing - it should have the same coords as ray

Mesh lineMesh = new Mesh();

lineMesh.setMode(Mesh.Mode.Lines);

lineMesh.setLineWidth(5f);

lineMesh.setBuffer(VertexBuffer.Type.Position, 3, new float[]{

playerPos.x,

playerPos.y,

playerPos.z,

rayCoords.x,

rayCoords.y,

rayCoords.z

});

lineMesh.setBuffer(VertexBuffer.Type.Index, 2, new short[]{ 0, 1 });

lineMesh.updateBound();

lineMesh.updateCounts();

line.setMesh(lineMesh);



shootables.collideWith(ray, results);



if (results.size() > 0) {

System.out.println("

Collisions? " + results.size() + "
");
float dist = results.getClosestCollision().getDistance();
Vector3f pt = results.getClosestCollision().getContactPoint();
String hit = results.getClosestCollision().getGeometry().getName();
System.out.println(" You shot " + hit + " at " + pt + ", " + dist + " wu away.");
if(pt != null){
mark.setLocalTranslation(pt);
rootNode.attachChild(mark);
System.out.println(mark.getLocalTranslation());
}
} else {
rootNode.detachChild(mark);
}
}
[/java]

What am I doing wrong? Why is the ray not lined up with the line?
If anyone needs more info, the full source is here: https://github.com/ildrean/TerraNullius/blob/master/com/Game.java
2

Bump

3

Why you do all that fancy stuff with normalizing to 0-1 and using polar coords?

https://wiki.jmonkeyengine.org/legacy/doku.php/jme3:math_for_dummies

https://wiki.jmonkeyengine.org/legacy/doku.php/jme3:advanced:mouse_picking

4

when you make a ray:



Ray ray = new Ray(playerPos, rayCoords);



you dont give it 2 points, you give it a starting point and a direction, you can use “cam.getDirection()” for the second parameter, in this case, since your doing “top down”, you should try giving it a normal vector of the angle your mouse makes in relation to your character…



Vector3f rayCoords = new Vector3f(((mousePos.x * 300) + playerPos.x), ((mousePos.y * 300) + playerPos.y), 1f);



that “1f” might very well be your problem, since that’s a direction, NOT a position, that is slightly moving the angle 1f to z, so if playerPos.z is 1f, the ray will slowly move up to 2f…

and will reach 2f after

x = playerPos.x + (((mousePos.x * 300) + playerPos.x)

and y = playerPos.y + ((mousePos.y * 300) + playerPos.y)

and after that it will keep moving z+=1 at that same rate…



then again, you should make your life easier and make a normal vector instead of using rayCoords as it is…



also, i see your using parts of “hello_picking” tutorial… i recommend you read it again and try to understand it fully…



hope this helps you…

cheers…