How do I match the rotation of a cube to a quad so it stays flat on it as I move it?-CodePudding

To keep it simple, I'm just trying to draw an arrow prefab along a quad that is at an angle. I need it to be flat against it (slightly raised) whatever position it's in.

What I'm doing right now is I've got a cube for the body of the arrow and a "triangle" prefab for the head. I click on the screen to get the "start position" (using a raycast hit point to make sure I'm over the my rotated quad below), then as I drag the mouse around it updates the "end position" vector 3. I simply calculate the distance between both points to see what "localScale.y" to expand it by, which works perfectly for the arrow length. For the head, I just attach it to the "end point", so it just follows the mouse.

The problem I have is that it isn't staying "flat" against the quad, which is rotated at X by 70 (in the inspector). And because of this, it rotates around length axis as I move and rotate the mouse in a circle.

Here my code:

 if (Physics.Raycast(mouseRay, out hit))
        {
            arrowEndPoint = hit.point;

            // Get rotation of Quad
            quadRotation = rotatedQuad.transform.rotation.eulerAngles.x;
            var arrowBodyRotation = simpleArrowBody.transform.rotation.eulerAngles;
            var arrowHeadRotation = simpleArrowHead.transform.rotation.eulerAngles;

            arrowBodyRotation.x = quadRotation;     // Doesn't seem to be affecting it
            arrowHeadRotation.x = quadRotation;

            // Follow arrow head to mouse
            simpleArrowHead.transform.position = arrowEndPoint;

            // Get distance between Start and End point
            arrowLength = Vector3.Distance(arrowStartPoint, arrowEndPoint);

            // Direction based on the start and end points
            var direction = (arrowEndPoint - arrowStartPoint).normalized;

            // Adjust scale and rotation of Body
            simpleArrowBody.transform.localScale = new Vector3(simpleArrowBody.transform.localScale.x, arrowLength, simpleArrowBody.transform.localScale.z);
            simpleArrowBody.transform.up = direction; 

            // Adjust rotation of Head
            simpleArrowHead.transform.up = direction;
            simpleArrowHead.transform.up = -rotatedQuad.transform.forward; // Didn't work
        }

CodePudding user response：

  quadRotation = rotatedQuad.transform.rotation.eulerAngles.x;
  var arrowBodyRotation = simpleArrowBody.transform.rotation.eulerAngles;
  var arrowHeadRotation = simpleArrowHead.transform.rotation.eulerAngles;

  arrowBodyRotation.x = quadRotation;     // Doesn't seem to be affecting it
  arrowHeadRotation.x = quadRotation;

of course this has no effect at all!

You are only assigning this to a local variable Vector3 (which is a struct and thereby a copied value).

If you wanted to actually apply this back you would e.g. use

quadRotation = rotatedQuad.transform.rotation.eulerAngles.x;
var arrowBodyRotation = simpleArrowBody.transform.rotation.eulerAngles;
var arrowHeadRotation = simpleArrowHead.transform.rotation.eulerAngles;

arrowBodyRotation.x = quadRotation;
arrowHeadRotation.x = quadRotation;

simpleArrowBody.transform.rotation.eulerAngles = arrowBodyRotation;
simpleArrowHead.transform.rotation.eulerAngles = arrowHeadRotation;

BUT note that