The trick to this is to place your spherecam at the same height as the camera in the other scene. That way their “eyes” match and the ground planes will line up.
If you are making a 360 for viewing (as if through the character’s eyes) then the camera should be at about 5 ft high (or a little less seems to be the average tv show camera height…).
The results of this render, the 2:1 image you have posted is called Equirectangular. This image is ready to wrap onto a sphere. In Carrara you can load it as the Background.
OK, I’ll try that on the next one. I just switched to a large non-spherical render and dropped it in as a background via postwork instead, since I could not get it to work properly. (result)
Thanks for the tip!
Nice picture! At the risk of going off-topic, if you applied a surface replicator to the suit and populated it with little spheres with an appropriate water shader, you could simulate a wet swim suit.