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Resolved Rotating force around pivot point

Discussion in 'Physics for ECS' started by NT_Ninetails, Sep 27, 2021.

  1. NT_Ninetails

    NT_Ninetails

    Joined:
    Jan 21, 2018
    Posts:
    196
    So i have been working on this issue for a while and I'm just stuck. I have 2 objects at (0,0,0) except they are rotated at different degrees.

    If I have ObjectA that has a Euler rotation of (0,0,0) and ObjectB has a Euler rotation of (0,90,0) then I use this code to get a relative force on B to be enacted on ObjectA

    Code (CSharp):
    1.  
    2. public static float3 RotateAround(float3 position, float3 pivotPoint, quaternion rot)
    3. {
    4.     return math.mul(rot, (position - pivotPoint)) + pivotPoint;
    5. }
    6.  
    7. /// <summary>
    8. /// Rotates a transform around the given Pivot point by the given rotation.
    9. /// </summary>
    10. /// <param name="transform"></param>
    11. /// <param name="pivotPoint"></param>
    12. /// <param name="rot"></param>
    13. /// <returns></returns>
    14. public static LocalToWorld RotateAround(LocalToWorld transform, float3 pivotPoint, quaternion rot)
    15. {
    16.     return new LocalToWorld
    17.     {
    18.         Value = new float4x4(math.mul(rot, transform.Rotation),
    19.             math.mul(rot, (transform.Position - pivotPoint)) + pivotPoint
    20.         )
    21.     };
    22. }
    23.  
    24. /// <summary>
    25. /// Rotates a transform around the given Pivot point by the given angle on the given axis.
    26. /// </summary>
    27. /// <param name="transform"></param>
    28. /// <param name="pivotPoint"></param>
    29. /// <param name="axis"></param>
    30. /// <param name="angle"></param>
    31. public static void RotateAround(Transform transform, Vector3 pivotPoint, Vector3 axis, float angle)
    32. {
    33.     Quaternion rot = Quaternion.AngleAxis(angle, axis);
    34.     transform.position = rot * (transform.position - pivotPoint) + pivotPoint;
    35.     transform.rotation = rot * transform.rotation;
    36. }
    37.  
    38. /// <summary>
    39. /// Rotates a transform around the given Pivot point by the given angle on the given axis.
    40. /// </summary>
    41. /// <param name="transform"></param>
    42. /// <param name="pivotPoint"></param>
    43. /// <param name="axis"></param>
    44. /// <param name="angle"></param>
    45. /// <returns></returns>
    46. public static LocalToWorld RotateAround(LocalToWorld transform, float3 pivotPoint, float3 axis, float angle)
    47. {
    48.     quaternion rot = quaternion.AxisAngle(axis, angle);
    49.     return new LocalToWorld
    50.     {
    51.         Value = new float4x4(
    52.             math.mul(rot, transform.Rotation),
    53.             math.mul(rot, (transform.Position - pivotPoint)) + pivotPoint)
    54.     };
    55. }
    56.  
    57. //NOTE ObjectB has a float3 position and a quaternion rotation
    58.  
    59. float3 m_lastCalculatedForce = (ObjectB.position - ObjectB_oldPosition);
    60.  
    61. float forceMagnitude = Unity.Mathematics.math.length(p.m_lastCalculatedForce);
    62. float3 unitForceVector = p.m_lastCalculatedForce / forceMagnitude;
    63. float3 newVector = TransformsExtensions.RotateAround(unitForceVector, float3.zero, math.inverse(ObjectB.rotation));
    64.  
    65. Debug.Log(p.m_lastCalculatedForce + "::" + forceMagnitude + "\n" +
    66.     "::" + unitForceVector + ":::" + math.length(unitForceVector) + "\n"
    67.     + newVector + ":::" + math.length(newVector));
    68.  
    69. p.m_lastCalculatedForce = newVector * forceMagnitude;

    This works only on the Y axis. the X and X rotation axis somehow messes everything up.
    Meaning i ObjectB is (90,0,0) and thie code runs then the force is in the wrong direction.

    Any ideas?
     
  2. NT_Ninetails

    NT_Ninetails

    Joined:
    Jan 21, 2018
    Posts:
    196
    I figured it our however another problem arose. here is the code i used if anyone is interested
    Code (CSharp):
    1.  public static Vector3 RotateDirectionVector(Vector3 direction, Vector3 rotation)
    2.         {
    3.             direction.Normalize();
    4.             Quaternion rot = Quaternion.Euler(rotation); // Rotate [angle] degrees about the x axis.
    5.             direction = rot * direction;
    6.             return direction;
    7.         }