(Solved) Aligning player to surface while still maintaining look direction

Question

Let's assume I have a sphere that can hover, so it has an offset from the ground. What I want is to simply rotate the sphere to match the normals of whatever is under it on the X and Z-axis, but still be able to rotate it to the direction in which it is travelling on the Y-axis. I have tried a few things that I found here on the forum and [2] seemed promising but unfortunately, it did not work.

 RaycastHit hit;
 if (Physics.Raycast(body.position, Vector3.down, out hit, 10, layerMask))
 { }   
 
 Quaternion groundTilt = Quaternion.FromToRotation(Vector3.up, hit.normal);
 body.rotation = Quaternion.Euler(0, currentMovementDirection.y, 0);
 body.rotation = groundTilt * body.rotation;

Here is a diagram of what I want, seen from top and side views. alt text

references: [1] https://answers.unity.com/questions/1347986/rotating-a-player-to-match-terrain-slope.html [2] https://forum.unity.com/threads/rotating-an-object-along-the-terrains-normal-whilst-looking-at-a-position.93570/

Answer 1

Best Answer

Answer by Namey5 · May 19, 2020 at 11:55 AM

You can use vector projection to find the relative forward vector between the ground's normal and your movement vector;

 if (Physics.Raycast (body.position, Vector3.down, out RaycastHit hit, 10f, layerMask))
 {
     //Up is just the normal
     Vector3 up = hit.normal;
     //Make sure the velocity is normalized
     Vector3 vel = currentMovementDirection.normalized;
     //Project the two vectors using the dot product
     Vector3 forward = vel - up * Vector3.Dot (vel, up);
 
     //Set the rotation with relative forward and up axes
     body.rotation = Quaternion.LookRotation (forward.normalized, up);
 }

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SteenPetersen · May 19, 2020 at 03:27 PM 0

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Hey there Namey thanks for your answer I've been reading up on your answer and although it seems to be correct I am getting unexpected results. Due to the nature of what I'm trying to do I need to rotate quite slowly.

I have used the following code:

 Quaternion newRot;
 
 if (Physics.Raycast(body.position, Vector3.down, out RaycastHit hit, 100f, layerMask))
 {
    Vector3 up = hit.normal;
    Vector3 vel = currentMovementDirection.normalized;
    Vector3 forward = vel + up * Vector3.Dot(vel, up);
 
    newRot = Quaternion.LookRotation(forward.normalized, up);
    body.rotation = Quaternion.RotateTowards(body.rotation, newRot, bodyRotationSpeed * Time.deltaTime);
 }

And what is happening is that he moves like Id expect while on a flat surface but when he gets to a ramp he seems to turn in the opposite direction. if you take my diagram from the OP the red dot starts to point down instead of up when entering the ramp.

Namey5 SteenPetersen · May 20, 2020 at 12:48 AM 0

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Whoops, I accidentally swapped the order of the projection - it was supposed to be a subtraction;

 Vector3 forward = vel - up * Vector3.Dot (vel, up);

I've also edited the original.

SteenPetersen Namey5 · May 20, 2020 at 06:02 AM 0

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Ahh, of course, I should have thought of that, I thought it was somehow my geometry that was off and was seeing if I could launch the ray diffrently.

(Solved) Aligning player to surface while still maintaining look direction

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