I understand that you want to connect follower pin of "Rigid Transform" block with the base pin of "Point on Surface Constraint" block. However, a direct connection is not possible due to difference in the nature of the ports. Have a look at the snapshots attached below for both the blocks.
For "Rigid Transform" block, both B and F are frame ports that represent base and follower frames respectively.
For "Point on Surface Constraint" block, B is a geometry port while F is a frame port.
Due to differences in the data types propagated by the frame port and the geometry port, it is not feasible to connect them together. Further, you can also observe the incompatibility by using the code for connecting these two blocks. Here is the code snippet for your reference
p1 = get_param(rigidTransform, 'PortHandles');
p2 = get_param(pointOnSurfaceConstraint, 'PortHandles');
add_line(gcs, p1.LConn, p2.RConn);
On executing the above code, you will get the following error which justifies why the connection is not possible.
The points input must only create line connections that follow connection rules of the
appropriate Physical Modeling domains
I hope this helps.
