lua.wetgenes.chipmunk.shape.query_segment
it = shape:query_segment(sx,sy,ex,ey,r)
Find the hitpoint along this raycast segment, from (sx,sy) to (ex,ey) with a radius of r.
Returns a table with the following info or nil for no hit
it.shape -- the shape
it.point_x -- the point of contact (x)
it.point_y -- the point of contact (y)
it.normal_x -- the normal at contact (x)
it.normal_y -- the normal at contact (y)
it.alpha -- how far along the segment the contact happened (0 to 1)