Known Problems

When VMD creates the output file it will try to match the current view and screen size. For the most part it does a good a job but there can be some problems. The colors in the final raster image can sometimes look different from what is seen in the VMD graphics window. This is because the external rendering programs use different shading equations and algorithms from what VMD uses.

The eye view can be slightly different between the VMD graphics window and externally rendered raster images. This occurs because the Screen Height and Screen Width (see here) values are not propagated to the output file, so the programs have slightly different transformation matrices. We have added an extra scaling factor, determined by trial and error, which reduces this effect for the default screen sizes, but the factor is only valid if the parameters are not changed.

The lights are supposed to be positioned in the output file as they are on the screen but not all formats support the number and type of lights available in VMD.

We have primarily tested the Tachyon and Raster3D output and have less experience with the other programs. The only problem we have found with Raster3D is if there are too many objects to render (this could easily occur when using `Tube' or `Ribbon' on large molecules), it will not render anything. (Raster3D documentation mentions an ``object limit''--Raster3D can be recompiled with a new limit.)