Circle object in Irrlicht?

[Scarabol]

Hey guys,

is there a circle object like line2d or point2d available?

I need to detect, if a line intersects with a 2d circle. Any ideas?

MfG
Scarabol

[CuteAlien]

You can use line2d::getClosestPoint and give it the center of your circle. Then subtract the result from the center and you get a vector from the center to the closest point on the line. Then you can check if that lines length is shorter than the circle radius in which case it collides.

[Scarabol]

Yeah right great! thx

But this method dont tell me the collision point(s).

MfG
Scarabol

[CuteAlien]

If you copy getClosestPoint from line2d.h and kick out out the 't' checks then it will no longer just return the closest point on the line-segment, but the closest point on the (infinite) line (let's call it X). X, the circle-center and each of the collision points form 2 right-angled triangles. You know the distance of X to the circle-center and the distance of the center to the collision points (the circle radius). So with A²+B²=C² you can get the length of the 3rd side of that triangle. That's the length you will have to add to X toward both directions of the line to get the collision-points.

But maybe take a look on the net, could be there's easier solutions for that (I was too lazy to google that now).