how to do sliding in 360 degrees movement

Hi guys

I think I manage to gather the necessary information to generate a sliding plane by raycasting with an axis aligned bounding box. My problem now is how do i apply the new velocity vector?

So to generate the destination vector and velocity this is what i do:



destinationPoint is simply position + velocity of the current player/object.

Currently, the way i move my object(plane) is relative to its last position, something like this:



That is without collision my problem is once I want to make sure that my ship slides when it collides with a obstacle this was my last attempt:



But I end up stuttering my plane or it won't slide at all. Either I'm applying it wrong or I'm not generating the new velocity correctly.

Thanks.

[Edited by - mickeyren on March 7, 2009 2:41:39 PM]

your obstacles are bounding boxes? how do you slide on them then? if they are a tris geometry then just fetch the normal of colliding triangle and if the normal has a large angle with y vertical axis take the normal and just add it to the object moving vector. that will couse the object to move a bit off the surface in the direction of slide

Just setting the destination point of the object to the new destination point (i.e. with the collision penetration removed) will give you 'sliding' behaviour, because you enter the collision plane obliquely and are expelled perpendicularly, giving you a net movement per frame.

Quote:

Original post by JohnnyCode your obstacles are bounding boxes? how do you slide on them then? if they are a tris geometry then just fetch the normal of colliding triangle and if the normal has a large angle with y vertical axis take the normal and just add it to the object moving vector. that will couse the object to move a bit off the surface in the direction of slide

Hi

Why do you sound like if i use bounding box i wouldn't be able to slide anymore?

Also, do I assume that the new destination point should always lie on the sliding plane?

hey guys

I have to break this down i'm still stuck.

My question is, does the new destination point will ALWAYS be on the sliding plane?

yes. That's sliding.

The typical sliding algorithm is to remove the component of the velocity along the collision plane normal.

If you have a collision time, intersection depth (if you are intersecting the box for some reason), and collision plane normal, the algo would look like...

object.velocity -= collision.normal * object.velocity.dotProduct(collision.normal); // slide velocity vector

A typical collision loop :

bool collide(Object& object, float timestep){    while(timestep > 1.0E-6f)    {        CollisionInfo collision;        bool collided = findCollision(object, timestep, collision); // find collision with object with a time limit.        // no collision detected. stop the collision detection loop        if(!collided)            break;        object.position += collision.normal * collision.penetrationDepth; // stop intersecting        object.position += object.velocity * collision.time; // move to the collision point in time        object.velocity -= collision.normal * object.velocity.dotProduct(collision.normal); // slide velocity vector        timestep -= collision.time; // reduce timestep, look for a new collison    }    object.position += object.velocity * timestep; // move object to the end of the timestep, where there is no collision}