ok success but looking back at yoiur post it's maybe not exactly what you wanted. But it's pretty cool anyways and it should show you roughly how to orientate the particles to the plane. 1. create a particle emitter. 2. create a small nurbs plane (to be instanced) and a large one (to collide with). Deform the big on e a bit so you can see this in action. 4.create some gravity for the particles. 5. make the large plane and the emitter collied together. 6.instance the small plane onto the particles. 7. add the collisionU and collisionV particle attributes. Add two more vector attributes (per particle arrays) one called normal and one called inverseNormal. These are th normals of the point of collision. 8. put this expression on the particleShape //CODE--------------------------------------- //object to collide with string $obj = "nurbsPlane2"; //dont really need to do this but it's easier float $cV = particleShape1.collisionV; float $cU = particleShape1.collisionU; //when collision occurs these values change so only do the next bit when they do! if($cU != -1 || $cV != -1) { //build up our pointone surface command. Which will return the xyz of the uv collision point string $tmp = "pointOnSurface -u "+ particleShape1.collisionU +" -v "+ particleShape1.collisionV +" -position nurbsPlane2"; //eval it float $collInfo[] = eval($tmp); //build up another command to do the same for the normal $tmp = "pointOnSurface -u "+ particleShape1.collisionU +" -v "+ particleShape1.collisionV +" -nn nurbsPlane2"; //eval it float $iNormal[] = eval($tmp); //assign the values to the vector attributes created earlier particleShape1.inverseNormal = <<$iNormal[0] * -1, $iNormal[1] * -1, $iNormal[2] * -1>>; particleShape1.normal = <<$iNormal[0], $iNormal[1], $iNormal[2]>>; } //CODE--------------------------------------- 9.set the particle instance options in the particleshape to be aimdirection: iNormal aimAxis: normal 10. Hit play... it's should work. check out the attatched scene file to see it working post again if it doesnt work. Alan My guess is no one here will know either, but I figured it was worth a shot. oh ye of little faith!!!