# Convert 3D point to 2D image point

Hi, using OpenCV what is the fastest/easiest way to convert 3D points to 2D image points. I know that the points are expressed in x, y and z coords in milimeters, I have the camera parameters, the height of the camera (relative to the ground plane) is expressed also in milimeters. I need an easy way to convert these 3d points (x,y,z expressed in mm) to 2d points (expressed in pixels) using the data I have and obtain the Xi, Yi coords where the origin of the coordinate system in the top left corner of the image.

Best regards!