If --enable-threads was used when configuring Vis5d, then the program uses multiple threads and CPUs (if available) to compute graphics in the background; thereby increasing vis5d's speed. Otherwise, vis5d tries to interleave the computation of graphics with user interaction. This results in the user interface being a bit sluggish until all pending graphics computations are completed.
The vis5d user interface may be complex to describe in words, but we have tried hard to make it simple in reality. After a little practice using the sample data sets we hope it feels natural.
Since version 3.2 of Vis5D there is a user-contributed software directory: contrib/. See the README file in that directory for a description of current contributions.