The SimProj Project provides a Processing-based (and therefore Java-based) application that provides a GUI for the simulated calculation of a video projection setup. SimProj allows to add and manipulate virtual projectors, mirrors and projection planes in order to show how the projection is mirrored and which sizes, angles and positions the setup components require. SimProj can be configured to comfortably show all necessary measures that can be ‘easily’ (everyone who has ever built a rear-projection setup knows what ‘easily’ means in that context) transferred to the hardware setup.
I downloaded the tool from the website but was not able to start it on my Mac running OS X 10.9. So like me, you maybe prefer using the SimProj online version.
If you have questions and remarks regarding SimProj, you will find a discussion about it in a Nuigroup forum post.
If you furthermore plan to build such a rear-projection setup, you will possibly find our mirror fixtures most helpful.