  The study of molecular dynamics simulations is largely facilitated by
analysis and visualization toolsets. However, these toolsets are often designed
for specific use cases and those only, while scripting extensions to such
toolsets is often exceedingly complicated. To overcome this problem, we
designed a software application called AViS which focuses on the extensibility
of analysis. By utilizing the dataflow programming (DFP) paradigm, algorithms
can be defined by execution graphs, and arbitrary data can be transferred
between nodes using visual connectors. Extension nodes can be implemented in
either Python, C++, and Fortran, and combined in the same algorithm. AViS
offers a comprehensive collection of nodes for sophisticated visualization
state modifications, thus greatly simplifying the rules for writing extensions.
Input files can also be read from the server automatically, and data is fetched
automatically to improve memory usage. In addition, the visualization system of
AViS uses physically-based rendering techniques, improving the 3D perception of
molecular structures for interactive visualization. By performing two case
studies on complex molecular systems, we show that the DFP workflow offers a
much higher level of flexibility and extensibility when compared to legacy
workflows. The software source code and binaries for Windows, MacOS, and Linux
are freely available at https://avis-md.github.io/.
