readme update

README.md

@@ -4,12 +4,12 @@ All content in this repo should be contributed with the intention of being openl
 
 This repo will be made public after initial setup.
 
-### What is svg?
+## What is svg?
 
 [Scalable Vector Graphics (svg)](https://en.wikipedia.org/wiki/Scalable_Vector_Graphics) is an open W3C standard for 2D vector graphics exchange over the world wide web. It is just a markup (xml) specification. svg files can be created, opened, and edited with any **plain text editor**. svg content can also be created with many open source or proprietary interactive graphics programs and can be viewed with any web browser. In the context of a web application, svg can be styled with css and scripted/animated with JavaScript.
 
 
-### Notes
+## Notes
 
 The type of svg graphics added to this git repo should primarily be a mix of simple line drawings, shading, and text. *Usage of raster/image data should be minimized.* Though svg files can contain images-- either as embedded data or as a hypertext link to remote url-- embedded images get encoded as a [base64 data format](https://developer.mozilla.org/en-US/docs/Web/HTTP/Basics_of_HTTP/Data_URIs) in svg graphics files. Base64 is a highly portable, but less efficient (e.g wasteful) way of storing real image data compared with raster formats like png/jpeg). Thus if the desired content does not require too many individual objects, it should just be composed as a vector graphic.
 
@@ -18,3 +18,9 @@ Graphics from here can then be openly patched into more complex figure/svg graph
 All are welcome to contribute. The free and open source [Inkscape](https://inkscape.org) drawing program is highly recommended for creating or editing svg graphics figures. Libreoffice has some nice diagramming tools as well. Graphviz (dot language) is good for diagrams of networks.
 
 <!-- Recommended workflow is to clone this repo locally, then make a working branch for yourself separate from the master branch while working on collaborative changes or adding new content. Then merge the changes with master. -->
+
+### Network diagrams
+
+With the open source graph visualization software [GraphViz](http://www.graphviz.org/) locally installed, the plain text `.dot` files can be edited and then rendered with a command like this:  
+
+`dot ppc-circuits.dot -Tsvg -o ppc-circuits.svg`