Spherical Projection Setup

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Spherical Projection Setup

Postby Jan Huewel » Wed Dec 16, 2009 10:56 pm

For those of you who like to setup spherical projections I have put together a few notes on how to setup 4 or more projectors for frontprojection

First of all it is important that when setting up the projectors that the softedge zones are equal between all projectors, at least this will get you faster to a good result.

I suggest to use a minimum of 4 Projectors as otherwise the Softedge zone might be to shallow.

Image

Once setup depending on the viewing position of the audience you might wnat to choose if you want to project onto the sphere from the bottom or from the top. This is related to the fact that the projector will not cover the sphere from the north to the south pole when setup at equator level.

If you need to do both poles you might need more projectors or a different projection setup i.e rear projection, not discussed in this post.

Image

So once the grid is aligned evenly around the globe you may want to wrap content around the sphere.

Please be aware that not every image or video loop might be suited for spherical projection as all the point at the top or bottom are weld into a single point, the north or sout pole.

As a sphere has an aspect ratio of 360°:180° (all the way around the sphere and top to bottom) this means you have an image aspect ratio of 2:1 if you want to use a single image or video file. In full HD this would require 1920x960pixel files.
Sometimes this resoltuion might be too small and 4 individual files need to be created.

As the content can setup in Pandoras Box in a rectangular way this means you can scale up a single layer and offset all Cameras over all outputs until the 4th projector matches the first one again.

To do this easily you can use a planar object that repeats it texture along the x axis see image below. This way the content designer only needs to create a 2:1 wraparound image without creating any additional softedge zones.

Image

I hope you got the main points on how to set this up. Please let me know if you require further informations.

All the best

Jan
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Re: Spherical Projection Setup

Postby deluca » Wed Sep 21, 2011 11:41 am

how to control four projectors?
thanks
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Re: Spherical Projection Setup

Postby Jan Huewel » Wed Sep 21, 2011 11:45 am

There are many ways on how this can be setup

one way I use very often is to use the X Offset of the Camera of each output to shift the projectors accordingly.

Best regards

Jan Huewel
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