Accurate collision detection...

Ok, here's the deal. I have a target and i want it to rez a tiny prim at the precise collision point that another object hits. Now this does not seem to work with llDetectedPos() as the object rezzed always appears a slight distance away from the skin of the object. How would i calculate a new position for the rezzed "Bullet Hole" that would be right against the surface of the prim struck, no matter the shape or size of the object? Would this need to be a calculation based on velocity? Any help here would be appreciated.

you'll find that velocity calculation isn't going to be very helpful, since by the time you get the information, it'll show the collided object in a new heading...

you CAN generalize and calculate the distance from the collision point to your surface, and then rez there... it won't be perfect and gets worse with angle, but considering the distance involved it's pretty close.

essentially you replace the axis position on the side that got collided with your own precalculated surface distance as a for instance take a default zero_rotation cube, inpacted from the top, and use the position you got from the impacting object, but replace the z value with a precalulated z of the objects center to it's top.... for rotated objects you can apply the inverse of your objects rotation to the position returned before calculating this, and then reapply you objects rotation.

it's all a PITA.

Also I believe that, with the exception of low-lag sims, that the physics calculations are only so precise anyway, meaning few collisions actually occur with real contact against the object.

So in a lot of cases the projectile /will/ collide a short distance from the target object.

Ok thanks all. i figured my math was right on the mark.