Camera Intrinsic Parameters


I am trying to find a simple way to retrieve the 3x3 camera intrinsic matrix from Panda3D:
[f_x, s , x_0;
0 , f_y, y_0;
0 , 0 , 1 ].
I defined a perspective lens in Panda3D and uploaded a model, I then used a picker ray to retrieve object points from a set of a given image points and I would like to feed those all to an OpenCV function cv2.solvePnPRansac ( the thing is that it seems like the camera matrix Panda3D created (following my perspective lens parameter) is different from what I thought it should. So I want to debug the issue, and for this cause I need to get the camera matrix out of Panda3D.
I read this post: [url][HACKED]matrix representation and projections],
but it is still not clear to me.
Can someone give me a hand on this matter.

This refers to the projection matrix, correct? This can be easily acquired using lens.getProjectionMat(). You may optionally pass in a coordinate system, like CS_yup_right if you are expecting results in a different coordinate system.