   Circle, semi-circle to Polygon collision Detection
  I have read through countless tutorials and samples, espcially http://www.metanetsoftware.com/technique/tutorialA.html as it was the closest to what I needed but I'm still failing to understand circle, semi-circle to polygon collision.Can anyone PLEASE, assist me. I am using the SAT method to do poly to poly collision. I want to use the same technique, or something better to determine the circular collisions.My problem with the tutorial at the link above is how to determine the line parallel to the vector generated between the centre of a circle to the centre of the mentioned AABB. I thought my physics, maths to code conversion was good but clearly it isn't.Assistance will be greatly GREATLY welcome   
  I am not sure if I got your problem right.If you really just want the parallel line then you have a ray given by the vector between the two centres andyou need some starting point for your line.I guess your problem is to create the point where the linestarts am I right?   ;  My apologies. I think I can get the parallel line. Any line obtained from a simple translation should yield a vector that is parallel to the original. i.e. given a vector v1, v2 will be parallel to v1 if we subtract a constant C from v1.v2 = v1 - CThis should mean the resulting vector v2 is parallel to v1 correct? If you might recall from my first post, v1 is the vector from the center of the circle to the AABB. The point considered on the AABB, according to the tutorial on metanetsoftware, is the center of the AABB. However, when I look at the implementation diagrams, it looks like the point considered on the AABB is actually the point nearest the circle. Is this right?Assuming the points are correct, v2 will now serve as a possible separating axis, as per the tutorial mentioned in the link (http://www.metanetsoftware.com/technique/tutorialA.html). I can now project my circle or semi-circle and my AABB onto v2.   