Fast Collision Detection

Question

I'm currently writing a android game and and am dealing with fast collision detections. I've come up with a solution, yet I'd like to know the most and preferred way to do this.

My solution: If we have a game object that moves 30 units a frame, we might go straight through another game object. So when I update I iterate the game object by 1 unit and run a collision detections until my wanted velocity is reached, and then I render.

This is a game object, that checks if the player's lasers or if the player itself has collided with it.

public void update(PlayerDroid[] holderPlayerDroid) {
            // Update the location
            //y = y + velocity;
            //stupidBadDroidPositionShape.setLocation(this.x, this.y);

            // Updates regarding interactions with the enemy out of the StupidBadDroids perspective, which is the PlayeDroid
            for(int numberOfPlayerDroid = 0; numberOfPlayerDroid < holderPlayerDroid.length; numberOfPlayerDroid++) {
                // Check if the StupidBadDroid got hit
                for(int iterations = 0; iterations < velocity; iterations++) {
                    y = y + 1;
                    stupidBadDroidPositionShape.setLocation(this.x, this.y);
                    // Check if StupidBadDroid collides with the enemy (which is the player)
                    if(Physics.shapeInShape(holderPlayerDroid[numberOfPlayerDroid].getPlayerPositionShape(), getPlayerPositionShape())) {
                        isDead = true;
                    }
                    for(int i = 0; i < holderPlayerDroid[numberOfPlayerDroid].amountOfVisibleLasers; i++) {
                        if(holderPlayerDroid[numberOfPlayerDroid].holderLaser[i].isDisposed() == false) {
                            if(Physics.shapeInShape(holderPlayerDroid[numberOfPlayerDroid].holderLaser[i].getLaserPositionShape(), getPlayerPositionShape())) {
                                isDead = true;
                                holderPlayerDroid[numberOfPlayerDroid].holderLaser[i].dispose();
                            }
                        }

                    }
                }



            }

    }

This way is very CPU demanding. Do you believe there are better solution I could apply?

Answer 1

You are describing tunneling, and are attempting to do continuous collision detection. Your method is CPU intensive because you are attempting to brute-force the solution.

The more fidelity that you want, the more technical the solution. If you don't need much fidelity, you could assume that the path the objects take in each frame is linear, and "expand" your hitboxes to cover the entire distance the objects moved during the frame. So, for example, instead of moving each point a discrete distance at a time, you could simply expand the points to a line segment and see if they intersect. Your hitboxes are not going to be points, though, so just "stretch" them by the path length. This is a very low-fi solution - if multiple collisions on the same object happen, you won't always pick the collision that happened "first".

For very complex solutions, try -

http://www.bulletphysics.org/mediawiki-1.5.8/index.php/Collision_Detection_and_Physics_FAQ