lua.wetgenes.chipmunk.space.query_segment_first
it = space:query_segment_first(sx,sy,ex,ey,r,group,categories,mask)
Find the shapes that are along this raycast segment, from (sx,sy) to (ex,ey) with a radius of r. Use group,categories and mask to filter the results.
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)