PlantUML uses Graphviz/DOT to compute node positionning for every UML diagrams (except Sequence Diagrams and Activity Beta Diagrams).
The fact that DOT computes automatically the position of node is a key feature, and algorithms implemented in
DOT usually give very good result.
However, there are some drawbacks of using DOT :
the computation is done by an external program (dot.exe on Windows, dot on linux), and that means that :
PlantUML has to create a new process for each diagram, (and communication with this new process could be source of bugs).
Users have to install DOT on their system, in addition of Java.
This means that it is possible to use PlantUML without installing GraphViz (which can be useful when you do not have administration right for example).
To do so, in addition to plantuml.jar, you must have:
vizjs: A Java library written by Andreas Studer that embed viz.js and call J2V8
The corresponding J2V8 implementation for your OS:
So, having the three files plantuml.jar, vizjs.jar and j2v8_XXXXX-3.1.6.jar in the very same folder (this is important) you can
run PlantUML without having GraphViz installed.
Finally, you have to set up the GRAPHVIZ_DOTenvironment variable value to vizjs
(or through the command line with -D flag or -graphvizdot flag).
Then, you can double-check your configuration by running the usual:
Note that this is only working with Java 8 (because of J2V8).
For complex diagrams (especially with labels on arrow), the solution is not working very well.
An issue has been opened on viz.js side (see Error when generating graph).
However, in that case, PlantUML falls back to some degrated solution.