Defishing for Flat Screens

You’ve officially finished a fulldome show. Now you’ve gotta get it out into the world. So you need a defished trailer that anyone can watch, not just the fulldome community. So you need to warp your domemasters to be flat.

This tutorial assumes you have the Navegar Fulldome Plugin for After Effects. Though I’m sure if you’re using other fulldome plugins (DomeXF, Digistar Virtual Projector) that the concepts will transfer.

Here is the big picture concept: We want to take domemasters (azimuthal equidistant / fisheye) as the input, change its placement on the dome, and then output to domemasters (azimuthal equidistant / fisheye).

domemaster-defish-tutorialWe have actually used this technique on more than just a trailer. We defished our whole 4k show and ended up with a 2708x1523px ready for flat screens. We also use the technique heavily when we are making a unidirectional version of the show, yet instead of defishing we are moving pre-rendered content to be best visibile in uni domes. Even still, sometimes we are forced to re-render a Maya scene because the springline is visible after moving the pre-rendered footage.

Of course this process isn’t perfect. But in almost all cases it’s better than simply cropping a domemaster directly. But the top-left and top-right corners will show a little warping. In other words, content in the corners areas will be slightly convex. But for the untrained eye it can be hard to spot. In fact, we just made a sale to a flat screen…

So this process will result in the trailer below. Once you understand the concept, you can then further refine the process by animating the altitude and rotation so that the best content is always within the green crop region. This takes quite some finesse but can really help when when your landing on a planet; you want the planet to remain circular while you’re flying towards it but then you want the horizon to be flat once you have landed.

update: 2015-11-09
— To squish more content into the 1080p crop zone, try adjusting the ‘Spherical Angle’ within the Navegar Fulldome Plugin. This will in effect increase the FOV and therefore allow you to see more within the cropped zone.
— If you have v3 of the fulldome plugin, the altitude will have a max limit of 90. This doesn’t mean you can’t use the defish technique. Instead make your attitude: 0 and azimuth: 0. Now it will appear upside-down but you can deal with that by pre-comping it.)

Update – 2016-03-26
— The defish technique is made even easier by using the Domemaster Fusion Macros. Below is a tutorial video in Fusion.

21 thoughts on “Defishing for Flat Screens

  1. Don’t expect blog posts to be overly technical. But this is what comments are best for, right? Is the uni-directional version a dome projection using a signal projector? Also, was wondering what a Springline is? Found the moon pass to be noticeably warped. But the rest was amazing good.

    • Using the term unidirectional or concentric refers to the direction of the seats. Unidirectional means the seats all face the same direction towards the dome. Concentric (or omnidirectional or panoramic) means the seats all face towards the center of the dome.

      Basically all domes have a different projector setup since each concrete dome is unique, differently sized, and has different technical demands. All 4k/8k domes use multiple projectors. The only single projector setups are 1k/2k in rez and are inflatable domes or mirror domes. We happen to run a 4k dome setup with 2 projectors, but there are other 4k domes that have 4+ projectors. 8k domes are a whole different story, needing more computers to keep the frame rate smooth. But when making a show there is no need to even think about how many projectors will be used because each dome has its own unique and unchanging slicing configuration that the distributor keeps in their records and then slices the domemasters for their specific dome upon buying a new show. And show producers have a copy of the slice software and process domemasters whenever they want to view 4k tests in their own dome.

      The springline is the outer edge of the domemaster (the literal edges of the dome). The zenith is the center of the domemaster (the tip-top of the dome). We use this jargon among the fulldome community so that we can easily speak about content in the dome. (domemaster = fisheye render = azimuthal equidistant)

  2. A question: once you have your frames out of the dome video, how to you stitch them back together into a trailer in After Effects?

    • I think I understand your question but I think you’re partly confused. Once you slice the domemasters for your specific dome, you can’t and shouldn’t re-stitch them. Once its gone through the dome slicer software its meant to be played only in the dome it was sliced for. So if you want to create a defished trailer then use the domemaster frames directly in After Effects with the Navegar Fulldom plugin; no need to slice.

  3. You can’t do this directly with E&S Virtual Projector, but a companion plug-in called Extract is made specifically for this purpose.

  4. You can do a perfect defish pretty easily.
    1. Map the dome master onto a polygonal disk with concentric circle and radial lines. (Actually, any fairly dense polygonalization will work)
    2. Translate the points to where they belong on the dome, Now you a hemisphere with the fulldome image on the outside.
    3. Evert the dome so that the image is on the inside.
    4. Place the camera at the origin and leave it there. At this point you can pan, tilt, and zoom and it will be exactly as if you were doing the same with a real camera panning and tilting about the nodal point. The linear perspective will be perfect. No curvature anywhere. You can even pan the camera to follow the action in the dome.
    I’ve done this for your picture. I’ll put an animation up on youtube of the process.

    • Ah I think I understand. You are placing a camera within a virtual dome with the domemaster on it. Our processes are identical in philosophy but differ in the tools we use. Thanks for sharing!

  5. There is no distortion introduced by placing the camera in a virtual. dome. Do you see the curvature of the horizon in your defishing? The horizon should be perfectly straight.

    With your process, the grid I introduced would have been curved following the curved horizon, which is not what an observer on Titan would photograph,

    My process is geometrically exact, exactly as if you were standing on Titan with a pinhole camera set for a 120 degree field of view. Pinhole cameras transform straight lines to straight lines, as you see in my animation.

    The results are different, as well as the tools.

    • Touché! I see what you mean. Have you tried this defishing process on a domemaster frame sequence? It can be tricky with something like a planet landing; where the planet is in the zenith and then you land on the surface.

      • I haven’t tried a sequence.Do you have a few frames I could run a test on? Or just a really rough storyboard of what you are talking about.
        The zenith of the dome is not special in any way. No special difficulties there.

  6. Pingback: Andrew Hazelden's Blog » Presenting the Dome2rect Fulldome Tool

  7. Thanks for the tutorial, Jason. One additional thing you might want to add (that we didn’t notice) is changing the Spherical Angle in the fulldome plugin to 220. Then you can get much more of the content.

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