Waveform viewer in VHDL simulators?
Typically, VHDL simulators like ModelSim have an interface similar to the IDE used in most software development.  This includes a text editing window, a console window, some log windows, variable "watch" windows, and one of those is a waveform display window.

For the waveform, you can typically select which signals to watch and how to display them.  A simple digital signal is obvious, but a bus can be displayed in various radix or as an analog value.  You also get the usual functions like zooming in/out and placing markers or cursors to more easily measure time. 

That's it.  Nothing more complex than that.