Let’s Make a Planetarium Show: Part 8 – Slicing
Ten computers, four projectors, and one 4K master frame sequence. How do we get all of this to play together?
Well, at this point we have our final 4K frame sequence on our NAS server. Now we have to make it into a movie format that can be played on all of our PCs, which goes out to all of our projectors.
Every planetarium is going to be a bit different in how they display their shows. We have four projectors in our theater: two shine to the north, two shine to the south. Each projector is fed an image from one of 8 computers. We have a master PC which controls all the “video” PCs and one “audio” PC. The two projectors that display to the north put out half of the final image; the other two projectors shining to the south put out the other half. We double stack our projectors for extra brightness so the two projectors at both north and south are really outputting the same image set. And each projector is being fed four different slices of the movie image for a total of eight slices.
So, what is a slice?
photo by Mark Petersen at Loch Ness Productions
Since we have a multi projection system, we have to slice everything up—each projector gets its own piece. Since we have a 60 foot dome here, we can’t really have one projector doing all the work for us. One projector displaying one image on a 60 foot dome just wouldn’t cut it. That’s why we have multiple projectors shining on their own designated section of the dome and outputting their own sliced section of the show.
In order to slice the show for the dome, I need to run it through Sky-Skan’s slicing software. This software is designed to take a frame sequence and slice it into sections, organize the slices into separate folders, and then convert each sliced section into their own .mkv file format. Just like the Digital Sky software, there is a master Slicing computer and 8 other slave PCs.
This can, again, be a lengthy process depending on the full length of the show. Not only does it have to slice each frame into certain sections, but it then also has to encode each section into a .mkv format when it’s done.
When I made the Pink Floyd eXperience show the whole thing came out to be around 52 minutes long and took over a week to slice and encode. I also constantly monitor the progress of all this using a program called TeamViewer.
I have all my work PCs connected to not only my home PC for access but also my phone. This way, in the middle of the night, I can check on a render or a certain job and restart it if errors occur, or if a project is done, I can then set up the next project to render.
So, as the project is now being sliced and encoded, it’s the perfect time to work on some surround sound audio effects.