I was looking this up..and i found a reference to it in the tricks book by andre lamothe. But im not a math guru so i dont really understand what hes going on about...Can somone explain how I detect a collision against a non perpendicular plane please, knowing that im not a math guru heh Thanks in advance Ash. Hmm i might aswell give you the info I have. this is an example of what i want to do: THE INITIAL VELOCITY VECTOR OF OUR OBJECT IS I=<4,-2> N'=<0,1> F = 2*N + I = 2*(-I . N')*N' + I =-2*(<4, - 2> . <0,1>) * <0,1> + <4, -2> =-2*(4*0 + -2*1) * <0,1> + <4,-2> = 4*<0,1> + <4, -2> heres what i know: - N' is the normal - N is the projection of I along N' heres what i dont know: why there is two velocity vectors..why is the normal classes as a velocity vector. What is the final product..the final velcoty vector inwhich i must use I think using the example it is (4,2) but im not sure at al.. somone help heh [edited by - ACAC on June 27, 2003 7:05:13 AM]