After we wrapped up most of our work on Doom, a lot of the team at Certain Affinity started work on remastering the classic Call of Duty: Modern Warfare. It was really exciting revisiting such an iconic title, and getting a master class in single player game design just seeing how it all worked.
As we were the first studio to start work on the title, I played a major role in writing tools that ported the content from the original game. We were working in a branch of the Advanced Warfare engine, and though things mostly worked the same, there were various patches to be made to work as intended with the new tech. We took the default position of parity: we’d do our best to preserve the design characteristics of the original game.
The Infinity Ward engine uses path nodes, rather than nav mesh, for its AI. There’s a build step that discovers which nodes are accessible to others nearby by “walking” between them. At runtime, the AI perform A* on the path node network to get to where they want to go. I was impressed by the iterative look-ahead algorithm used to prevent the AI from looking robotic while pathing through the network. I studied up thoroughly on how the AI’s pathing, navigation, and root-motion animation system worked in order to debug and fix various issues that came up. It was really cool to see such significantly improved locomotion applied, adding a lot of flavor through the new logic and animations.
As we were redoing the original maps, we discovered that certain changes to the geometry would break the AI. If certain AI couldn’t get from point A to B, or the timing of that path changed significantly, the game would break - possibly subtly. In order to help the level designers police content changes effectively, I built the Path Validator tool. This would compare the current path network against the “approved” baseline network, and warn about any significant changes. Other team members would integrate this tool into Radiant so that there was a clean workflow to reviewing and approving changes to the path network.
Though I was initially frustrated by the lack of the C++-isms that had been introduced in the latest idTech, I found some advantages to the more old-school C-style approach the COD tech employed. For debugging challenging issues, I created some global scratch variables (vectors and such). I was able to perform most math operations on the scratch space while paused in the debugger. Because C++ is a lot more allocation-oriented, certain operations just can’t really be performed from the Immediate Window in the debugger; however, I was able to dynamically perform vector operations so that I could execute Debug Draw commands to visualize arbitrary information when I was having a hard time grasping what I was seeing in the debugger. Combine that with a very robust replay system, and I found most issues were really easy to debug in the tech!