C4 is a gaming/graphics engine written by Eric Lengyel at Terathon Inc. While it has some shortcomings because it's being created by a single guy, it's also pretty nice in many areas, and packs a solid graphics punch. At times, I fool around with this engine, and this page collects some information I gather about it.

Pathfinding

Read my article on pathfinding in C4 which actually includes code for a complete art path for authoring navigation meshes (networks) and doing A-star pathfinding throughout levels. You might find it useful if you want NPCs that walk around the level, for example.

Download the code if you want to actually use it, or just to read it.

Conditional Scripting

The graphical scripting language of C4 doesn't support conditional execution, by default. This article describes how to implement a script method that will execute its submethods only if a given console variable has a certain value. You get to set the name of the variable, the reference value, and the comparison function (equal, less than, etc). Note that console variables are NOT game state, so you will have to do something else to make decisions based on game state.

Download the code if you want to actually use it, or just to read it.