[Solved]Terrain: Rotatating an object to the hit.normal + manual rotation

-I have set up a script that shoots a ray at the terrain.

-An object follows the hit.point

-The object rotates towards the hit.normal

-The object is able to be rotated along its local Y axis - this is where I am stuck since Y is not always “up”

Manually I can achieve what I want by rotating the Y axis of the object locally in the scene view while paused but I would like to achieve this through script.

Prior to adding in the hit.normal rotation this script worked how I would like minus the following of the hit.normal.

I know I am missing a step and I probably need to store the FromToRotation somewhere and add desired rotation, but I am a little lost on how to achieve it since I cannot just rotate the y axis alone.

Thanks

			RaycastHit hit;
			Ray ray = Camera.main.ScreenPointToRay (Input.mousePosition);

			if (Physics.Raycast (ray, out hit, Mathf.Infinity, canBuildLayers)) {
				spawnpoint = hit.point;
			}

			Vector3 rotateNeg = new Vector3 ( thingToPlace.transform.localEulerAngles.x, thingToPlace.transform.localEulerAngles.y - 22.50000f,  thingToPlace.transform.localEulerAngles.z);
			Vector3 rotatePos = new Vector3 ( thingToPlace.transform.localEulerAngles.x, thingToPlace.transform.localEulerAngles.y + 22.50000f,  thingToPlace.transform.localEulerAngles.z);
			Vector3 slightRotateNeg = new Vector3 (thingToPlace.transform.localEulerAngles.x, thingToPlace.transform.localEulerAngles.y - 5.00000f, thingToPlace.transform.localEulerAngles.z);
			Vector3 slightRotatePos = new Vector3 (thingToPlace.transform.localEulerAngles.x, thingToPlace.transform.localEulerAngles.y + 5.00000f, thingToPlace.transform.localEulerAngles.z);
			
			if (Input.GetAxis ("Mouse ScrollWheel") < 0) {
				if(Input.GetKey (KeyCode.LeftAlt)){
					thingToPlace.transform.eulerAngles = slightRotateNeg;
				}else{
					thingToPlace.transform.eulerAngles = rotateNeg;
				}
			} else if (Input.GetAxis ("Mouse ScrollWheel") > 0) {
				if(Input.GetKey (KeyCode.LeftAlt)){
					thingToPlace.transform.eulerAngles = slightRotatePos;
				}else{
					thingToPlace.transform.eulerAngles = rotatePos;
				}
				
			}

			thingToPlace.transform.position = spawnpoint;
			thingToPlace.transform.rotation = Quaternion.FromToRotation(Vector3.up, hit.normal); // TODO newly added to align to terrain. follows terrain but does not allow rotation

Got it!

Storing the rotation and multiplying solved it. New script for anyone who is interested. It allows you to have an object follow your mouse along the terrain’s normal and rotate it along its y axis:

Vector3 rotateTo = new Vector3(0,0,0);

			RaycastHit hit;
			Ray ray = Camera.main.ScreenPointToRay (Input.mousePosition);

			if (Physics.Raycast (ray, out hit, Mathf.Infinity, canBuildLayers)) {
				spawnpoint = hit.point;
			}

			Vector3 rotateNeg = new Vector3 ( 0, rotateTo.y - 22.50000f,  0);
			Vector3 rotatePos = new Vector3 ( 0, rotateTo.y + 22.50000f,  0);
			Vector3 slightRotateNeg = new Vector3 (0, rotateTo.y - 5.00000f, 0);
			Vector3 slightRotatePos = new Vector3 (0, rotateTo.y + 5.00000f, 0);
			
			if (Input.GetAxis ("Mouse ScrollWheel") < 0) {
				if(Input.GetKey (KeyCode.LeftAlt)){
					rotateTo = slightRotateNeg;
				}else{
					rotateTo= rotateNeg;
				}
			} else if (Input.GetAxis ("Mouse ScrollWheel") > 0) {
				if(Input.GetKey (KeyCode.LeftAlt)){
					rotateTo = slightRotatePos;
				}else{
					rotateTo = rotatePos;
				}
				
			}

			thingToPlace.transform.position = spawnpoint;
			thingToPlace.transform.rotation = Quaternion.FromToRotation(Vector3.up, hit.normal) * Quaternion.Euler(rotateTo.x, rotateTo.y, rotateTo.z);