small video describing how it worked in cinelerra-cv 1.2.1 using old dynebolic 1.4 iso

In checking the above, I ended up clicking on: http://cinelerra-cv.wikidot.com/cincvdocs:docs-start

I do not comprehend what the point of providing links to obvious documentation for CinGG without including the CinGG manual in full? Like the documents by RafaMar and Magyar (Hungarian).

I wonder how "long" must be long distance? offscreen? tried this, also with enlarged projector range .... no two boxes! I can't even see this behavior in cincv 2.3.* from 2017, but may be I am doing it wrong for all versions?

I finally tried it on a couple of older versions and could never get any extra boxes so obviously you were not doing anything wrong. The second box is also documented in the original HV manual - Secrets of Cinelerra (2009 version). Portions of the CinGG manual were obtained from that manual when I was at a total loss which was quite frequent.