Debugging Features

Debugging Features

Have you ever spent countless hours trying to identify why a mechanic doesn’t work only to realize that it was a small oversight on logic? In this post I’m going to outline some of the techniques I use when I try to identify the source of a code bug.

Meta Horizon Worlds has a few features that allow us to troubleshoot and test the functionality of scripts. Some of them are straightforward, but others are not technically features made for debugging purposes, but I find them very useful when understanding the execution flow:

•         Console logs: These are the standard console.log, console.warn, console.error in TypeScript, and the equivalent *debug print* under the Values tab in Code Blocks. With these APIs we can “print” messages to flag if a particular part of the script runs, or to preview the changes of a variable. When using console logs (or debug print) it is recommended to standardize the structure of the log messages. Sometimes these logs are generated very fast and from different scripts, so it’s important to know in what order they are being called and executed. In the Desktop Editor, you can see logs in the “Console” tab; in VR, you can find the logs in the Build Menu.
•          Debug Console: This is a gizmo that you can place in your world to see the logs in preview and published mode. This feature helps to identify real time errors that never appear when creating the world. One of the things that I like to do is to make this gizmo part of a wearable or grabbable that I carry around in published mode, or make it appear when I press a button. This makes the Debug Console always available if something goes wrong.
•         Pop-ups: This is one of the unintended debug features. If the logs are not too repetitive, I prefer to use pop-ups to know if a particular part of the code runs while previewing a mechanic. It shows right in front of me, this way I don’t have to lose attention to the experience to look away at the console log. This is also more applicable for VR playtesting. In Desktop Editor, you can see the Console log all the time while testing a game.
•          NPC Gizmo: This is one of the most recent Meta Horizon Worlds features. It allows you to spawn a player avatar, generating the same events as a real player would: player enter/exit world, player enter/exit trigger, and so on. I like to use this gizmo when debugging multiplayer mechanics. Real testers are not always available, but the NPCs can be used as a placeholder visitor. Note that to test interactions with an NPC (grab, move, look…) does require TypeScript scripting.
•         Text and Custom UI gizmos: These are another alternative to the Debug Console. You can personalize these display features to print the output of your logs. My favorite implementation of this was a CUI overlay that only appeared for the collaborators of a world after pressing a key. It’s like having special X-Rays to troubleshoot an experience.

When something goes wrong, try to reduce the amount of logic that runs at once; and continue to iterate into smaller and smaller chunks of code to isolate the true cause of a bug.

Last, always remember to remove or disable the console logs and test features once you are ready to publish your world!