koobas.hobune.stream
Find direction on a sphere?
I want objects to rotate around the point in space. Imagine how the vertices move when you rotate a sphere mesh. They rotate using a matrix. I tried to do the same way and it works but super slow. For 40 objects in FixedUpdated it destroys my FPS on mobile.
Is there a faster way to get a direction on a sphere?
Img: red vectors - point direction, green dir - sphereMovementDir 
/// <summary>
///
/// </summary>
/// <param name="sphereMovementDir">direction the sphere moves in space</param>
/// <param name="sphereCenter">sphere center in world coordinates</param>
/// <param name="point">point on a sphere in world coordinates</param>
/// <returns></returns>
public Vector3 GetDirOnASphere(Vector3 sphereMovementDir, Vector3 sphereCenter, Vector3 point)
{
//transform sphereMovementDir to the rotation direction. Like a rotation of roll
Quaternion lookRot = Quaternion.Euler(sphereMovementDir.z, 0f, -sphereMovementDir.x);
//matrix that rotate smth using lookRot
Matrix4x4 m = Matrix4x4.Rotate(lookRot);
//calculate a new position for point after we applied rotation matrix
Vector3 newPointPos = sphereCenter + m.MultiplyPoint3x4(point - sphereCenter);
//get direction of movement on a point of a sphere
Vector3 forceDir = (newPointPos - point).normalized;
//return the dir so then I can apply it to the point...velocity
return forceDir;
}
Best Answer
I have found the mistake. I should compile a matrix out of the method and pass it as an argument. Because for each vertex rotation matrix is the same and no need to calculate it in the method
