EarthDesk in a Dome

The following allows one to display current/live Earth images interactively on a planetarium dome (or iDome) using either a fisheye projection system or a spherical mirror based system. It uses EarthDesk to generate the spherical projections, and Quartz Composer to manage the display. It is provided mainly as a demonstration for those who may not have used Quartz Composer, an excellent tool for interactive graphics.

Quartz Composer is supplied free of charge with the Apple XCode development systems (also free). You are encouraged to look through the Quartz Composer patch in order to understand what is occuring. When you are ready to run the composition you need to enter full screen mode.

"pbmesh" is a Quartz Composer patch that implements the image warping technique used by the author to warp fisheye images for spherical mirror based projection (although it has a much wider range of application). pbmesh is also free, it needs to be copied into
   /Library/Graphics/Quartz Composer Patches
This must be exactly as shown above, it is NOT the same as a similar appearing directory called "Quartz Composer Plugins".

EarthDesk needs to be configured to save the image to a file rather than place it on the desktop. The setting for this is in the general preferences pane. The Quartz Composer patch will read this file at a time interval of the users choice.

EarthDesk: Projection and zoom settings

EarthDesk needs to be instructed to create an equirectangular projection, it is this projection that the Quartz Composer patch will wrap onto a sphere. It would be nice if EarthDesk had an option for a perfect 360 degree horizontal range, since it doesn't the user needs to adjust the zoom so that at least 360 degrees are visible. Controls are provided in the Quartz Composer composition to trim the resulting image to 360 x 180 degrees before wrapping onto the sphere.

Quartz Composer Composition

The Quartz Composer composition is well commented. The following indicates some of the more important adjustments. The reader is encouraged to explore Quartz Composer, it is a very capable environment in which to create dynamic visual displays, including for planetariums. It should be noted here there is a slight "hack" involved, that is, a fisheye image isn't actually generated. It relies on the fact that to a first approximation a circular objects in fisheye space is also circular.

iDome example