Along with the various Matrox multimonitor graphics cards and the TripleHead2Go expansion module comes a feature called Matrox Monitor Bezel Management. Using the software, you can achieve a seamless desktop over multiple monitors.
It is reached via the Matrox PowerDesk software interface.
In the edit mode, you can make up for the bezel between screens by entering the bezel width in pixels in the Hidden pixels field.
This allows you to create seamless multi-screen material in DISE Composer, to be run on a single DISE Replay.
Note: The tool only supports screens with identical resolutions. If you have want to support different resolutions, the way to go is a DISE NoBorders setup.
Read more: Matrox Monitor Bezel Management white paper