Spatial Data Structures for moving objects?

Question

I was wondering what is the best data structure to deal with a lot of moving objects(spheres, triangles, boxes, points, etc)? I\'m trying to answer two questions, Nearest Neigh

Answer 1

1. You can partition the scene in an octree and utilize scene coherence. Your moving object that you are testing is going to be in a specific node of the tree for a specific amount of frames depending on its speed. This means you can assume it will be in the node and therefore quickly cut out a lot of objects that are not in the node. Of course the tricky bit is when your object is close to the edge of your partition, you would have to make sure you update which node the object is in.

2. A moving object has a direction and a speed. You can easily divide the scene in two sections by using a perpendicular division from your objects direction of movement. Any object on the wrong side of this division do not need to be checked. Of course compensate for the other object's velocity. So if the other object is reasonable slow, you can easily cut it out from further checks.

3. Always simplify whatever shape you are testing with something like an axis aligned bounding box. An initial collision test

4. You can take the distance between your object and another moving object plus the velocities. If the other moving object is moving in the same general direction at a faster velocity, you can eliminate it from your check.

5. There are many other optimizations depending on the object's shape. Circles or squares or more complex shapes all have specific optimizations you can do while moving.

6. Assuming some objects do stop or can stop moving, you can keep track of objects that stop. these objects can than be treated like static objects and therefore the checks are faster and you can apply all the static optimization techniques to them.

7. I know of more but can't think of any off the top of my head. Haven't done this in a while.

Now of course this depends on how you are doing the collision detection. Are you incrementally updating the object's position based on velocity and checking as though it is static. Or are you compensating for velocity by extruding the shape and figuring out initial collision points. The former needs a small step for fast moving object. The latter is more complicated and costly but gives better results. Also if you are going to have rotating objects then things get a little more tricky.