I just read through the patent claims for patent #4,734,690. This is the patent that was purchased from Tektronix by a Texas-based firm that decided to sue every single company that used any part of it. This patent covers a method of translating a 3D image to a 2D image.
The patent was applied for April 6, 1987 and was granted March 29, 1988.
What was really funny about all of this is that large chunks of the algorithm are identical to the algorithm used to do the exact same thing printed on pages 296-398 of "The Art of Graphics for the IBM PC" by Jim McGregor and Alan Watt, which was first printed in 1986 by Addison-Wesley Publishers Limited.
Because of frivolous suits like this, lots of people believe that the patent system is broken and should be overhauled. Personally, I believe that the patent system as a whole works with some minor issues, so any changes should be minor and specifically tailored to fix the problem at hand.
The biggest problem nowadays is patent houses buying up patents from other companies and using this newfound intellectual property to sue other people who had been using the patent for years. Easiest solution to this problem? Don't allow patents to be sold or assigned in full, only licensed or cross-licensed. The reasoning behind this is quite simple. Patents exist to protect the rights of the original inventor for a brief period of time.
Software patents are broken as well, but it's going to take some time to decide what the smallest change necessary to fix them will be.