We're using solvePnP to determine the attitude of an object with its center of rotation fixed relative to the camera (object has some aruco markers on it). And I know for a fact that coordinates of the center of the object are constant. Those coordinates are in tvec returned from solvePnP. I just need the object's rotation rvec, but solvePnP doesn't seem to provide a way to tell it that there's no need to optimize tvec because I already know it. The optimization process would have been easier, faster and most importantly more accurate if we had a way to do that, but judging by the code of cvFindExtrinsicCameraParams2 function it's not the case. At least not for SOLVEPNP_ITERATIVE algorithm that we're using.
So is there a way to use solvePnP to only optimize rotation if I already know tvec? I know that I can provide it as initial guess, but I want to exclude it from optimization altogether.