Look Rotation Viewing Vector Is Zero log every update (#895)

* Update Follow.cs

Signed-off-by: Niek Eichner <[email protected]>

* Update according to comment.

Signed-off-by: Niek Eichner <[email protected]>

* Add a few doc clarifications

* Update CHANGELOG.md

* Use epsilon instead of 0

---------

Signed-off-by: Niek Eichner <[email protected]>
Co-authored-by: Kurtis <[email protected]>
Co-authored-by: Kurtis <[email protected]>

Author: neichner

org.mixedrealitytoolkit.spatialmanipulation/CHANGELOG.md

@@ -13,6 +13,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 * Fixed tap to place `StartPlacement()` when called just after instantiation of the component. [PR #785](https://github.com/MixedRealityToolkit/MixedRealityToolkit-Unity/pull/785)
 * Fix null ref in SpatialManipulationReticle when multiple interactables are hovered. [PR #873](https://github.com/MixedRealityToolkit/MixedRealityToolkit-Unity/pull/873)
 * ConstantViewSize solver now retains the initial scale and aspect ratio [PR #719](https://github.com/MixedRealityToolkit/MixedRealityToolkit-Unity/pull/719)
+* Fixed Follow solver frequently logging "Look Rotation Viewing Vector Is Zero" [PR #895](https://github.com/MixedRealityToolkit/MixedRealityToolkit-Unity/pull/895)
 
 ## [3.3.0] - 2024-04-30
 

org.mixedrealitytoolkit.spatialmanipulation/Solvers/Follow.cs

@@ -462,20 +462,27 @@ private float SimplifyAngle(float angle)
         /// local xz and yz planes. If these angles fall within the leashing bounds, then we don't have
         /// to modify refForward. Otherwise, we apply a correction rotation to bring it within bounds.
         /// </summary>
+        /// <returns>Whether <paramref name="refForward"/> was clamped or not.</returns>
         private bool AngularClamp(Vector3 refPosition, Quaternion refRotation, Vector3 currentPosition, ref Vector3 refForward)
         {
             using (AngularClampPerfMarker.Auto())
             {
                 Vector3 toTarget = currentPosition - refPosition;
                 float currentDistance = toTarget.magnitude;
-                if (currentDistance <= 0)
+                if (currentDistance <= Mathf.Epsilon)
                 {
                     // No need to clamp
                     return false;
                 }
 
                 toTarget.Normalize();
 
+                if (toTarget == Vector3.zero)
+                {
+                    // No need to clamp
+                    return false;
+                }
+
                 // Start off with a rotation towards the target. If it's within leashing bounds, we can leave it alone.
                 Quaternion rotation = Quaternion.LookRotation(toTarget, Vector3.up);