Rotating object to face target, while being rotated to match terrain slope

Questions & Answers
1

alt text

In the image above

  • the red vector is the spider’s forward vector
  • the blue vector is the vector representing the direction between the spider and it’s target

In the code below, orientation is a vector that’s representing the normal of the terrain, so that the spider gets aligned to it:

`

Quaternion rotationNeeded = Quaternion.FromToRotation(Vector3.up, orientation);

transform.rotation = Quaternion.RotateTowards(
            transform.rotation,
            rotationNeeded,
            RotationSpeed * Time.deltaTime
);

`

My issue is that I cannot manage to make the spider face its target… When I add any code that would make it rotate towards it, then it’s not aligned with the terrain’s normals…

2

Found the solution, thanks to stackoverflow and this answer here: https://forum.unity.com/threads/look-at-object-while-aligned-to-surface.515743/ (which solves this issue https://i.imgur.com/NPwHzpx.png)

`
``



// target is the player

// transform is the spider


Vector3 orientation = GetTerrainNormal();
Vector3 directionToTarget = (target.position - transform.position).Y(0);
float d = Vector3.Dot(directionToTarget, orientation);
directionToTarget -= d * orientation;
if (directionToTarget.sqrMagnitude > 0.00001f) {
    directionToTarget.Normalize();
    Quaternion rotationNeeded = Quaternion.LookRotation(directionToTarget, orientation);

    transform.rotation = Quaternion.RotateTowards(
        transform.rotation,
        rotationNeeded,
        xRotationSpeed * Time.deltaTime
    );
}
`

Maybe it’ll be useful to someone one day :smiley: