any sample code or documentation on creating fire using particle systems in a 3D environment???
You basically just want to look at how to create particle systems, which is well covered by the docs. Just dig into the particle panel, try to understand how the different parameters affect your system. When you save out the particle definition, you can plug the output into your own class and control the parameters from within your code so you can have the fire increase in intensity etc.
If you can use panda’s particle system (being able to use the particle panel should be +/- enough) but are unsure of how to create a good looking fire effect with it, you can try to look for an article that covers how to do it. Since the basics of most particle systems are the same, you don’t need a panda3d specific tutorial about it. Once you get a decent texture(s) for the fire particles you basicly just play around with the settings in the particle panel until the fire looks good