rayCast 
  Ray-cast the world for all fixtures in the path of the ray.
The ray-cast ignores shapes that contain the starting point.
Parameters
start
the ray starting point.
end
the ray ending point.
callback
a user implemented callback called on every fixture hit.
See also
fun World.rayCast(startX: Float, startY: Float, endX: Float, endY: Float, callback: KtxRayCastCallback)
Ray-cast the world for all fixtures in the path of the ray.
The ray-cast ignores shapes that contain the starting point.
Parameters
startX 
the ray starting point X.
startY 
the ray starting point Y.
endX 
the ray ending point X.
endY 
the ray ending point Y.
callback
a user implemented callback called on every fixture hit.