help With rotating vectors

trying to rotate my quaternion quat_1 about quatternion quat_2_new and find new position. Was curious how to do this.

Answer 1

[James Tursa]

We need more detail. Your quat_2_new is a unit quaternion, so it can be used for rotations. If your quat_1 is just supposed to be an arbitrary 3D vector expressed as a quaternion, then rotating quat_1 could be either of these two expressions

quat_1_rotated = inv(quat_2_new) * quat_1 * quat_2_new

or

quat_1_rotated = quat_2_new * quat_1 * inv(quat_2_new)

Where the * is a quaternion multiply. Which of these expressions applies in your situation depends on what these quaternions represent (vector rotation or coordinate transformation) and what the quaternion convention being used is.