Software Bisque and spherical mirror projection: A review

Written by Paul Bourke
January 2009


The following is the result of an exploration of the "Software Bisque" fulldome products and their handling of projection using a spherical mirror and the warp maps that describe how to distort fisheye images for this projection technique. This is not an endorsement of the products for their intended users but simply a test/evaluation of the fisheye warping. The discussion here relates to capabilities in the "Theatre edition".

The most positive aspect is that they use the standard warp maps as used by the warp-on-the-fly movie player and supported by the custom mesh generator. This means that sites who have gone through the process of creating a precise warp mesh for their configuration can use that directly with both Seeker and SkyX. The tests performed here are in an upright dome, not necessarily the natural choice for astronomy content, but in a way this shows the power of the use of warp maps, that is, the application doesn't need to know anything about the projection hardware and all tools use the same mesh warp configuration file.

Seeker

The selection of the warp map could not be simpler, see image below. In the tests performed here an HD (1920x1080) projector is used and the dome and screen display are in mirror mode.

SkyX

Unlike Seeker, SkyX was operated with distinct displays (not mirrored). The control panels on the LCD display and the content fullscreen on the secondary display attached to the projector.

Notes and Issues

  • The selection of the warp map files expects an extension of ".map". This was an early convention by the author but for various reasons they are now generally called ".data" files. No big deal since the file can easily be duplicated and renamed but perhaps any text file text file should qualify.

  • The distribution provides a truncated fisheye option, of course that and other specialist configurations can also be dealt with warp maps.

  • At the time of writing there seem to be some issues with the particular ATI card being used. This resulted in stars being drawn incorrectly. The problem was not exhibited with the same version of the software on a machine with an nVidia card. The seriousness of this problem is unknown, users may choose to check the status of compatibility with their particular graphics card.

  • I repeat that the upright dome is not necessarily an ideal environment for astronomy content, but one way to address some of the spatial issues is to rotate the horizon by 90 degrees. Unfortunately it seems SkyX only presents one hemisphere, so doing the rotation while possible results in no graphics on the lower half of the iDome. Not an issue for a "standard" planetarium dome, could be an issue for a tilted dome.