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Behind the scenes - Debugging DOOM
🕑 Added 2020-04-08 18:00:03 +0000 UTCHello everyone! Time for a sneaky behind the scenes look at the video-making process. Today, I want to talk about a strange thing I sometimes have to do to make the show work: cheat!
Something I’ve been experimenting with during most of GMTK is using cheats, debug modes, and editing game files to help with my analysis, and to procure those pretty video clips you see in my videos.
So to get the nice shots of Miami in the Hitman 2 video, I put on a cheat that makes Agent 47 invisible to guards so that I could hide in a corner and point the camera at the event in question. I’ve used similar techniques in lots of videos.
For Hollow Knight Boss Keys, I used a hidden debug menu to hide the Knight, remove the vignette effect, and zoom out the camera - allowing me to get those gorgeous shots of the game’s levels. Similarly I used a debug mode to remove the film grain on Cuphead, to make the graphics in the random episode.
And in the Prey video, I used a whole bunch of tools to lift the 3D model of the Gloo cannon and its texture for the game’s files, and then imported them into 3DS Max, to get that shot of the gun spinning around. I also explored the game files for the Event[0] breakdown, which revealed a massive spreadsheet of responses that helped me figure out exactly how Kaizo worked.
I’ll also use cheats to skip through games, sometimes. Unlike those making video essays on movies, who can just scrub through to the part they want to show, making essays on games can sometimes mean playing a game for 5 hours just to reach the level you want to talk about! Throwing on infinite health and ammo can make that much less of a slog!
Anyway, this stuff really came in handy during the DOOM Eternal video, too. It started by finding a way to reenable the game’s console. Basically, most big games have lots of secret options that allow you to cheat, turn systems on and off, and output information about how the game works - all for testing purposes. These are usually disabled before the game goes live, but there’s often a way to turn them back on.
So the DOOM Eternal console allowed me to type things like “god”, to turn on god mode (making you invincible, for those who missed 90s shooters on PC!) and “g_showhud 0” to turn off the HUD entirely.
A really helpful one was “notarget”. This made the demons completely ignore me and just stand on the spot. That was great for the portrait shots of the demons, but also to find out how the spawns worked on that level. I could kill and injure demons and see the exact conditions that needed to be met for demons to spawn - and the location they appeared.
Another one I discovered was “photomode_freeCamLeashDistance”. Photo modes can be helpful in GMTK for taking the game’s camera to weird and awkward locations, but they’re a bit limited because the game world stays static and you can only move the camera in a small orbit around the hero. Not in DOOM Eternal! For one, the game actually allows you to move time forward in the photo mode. And by changing the LeashDistance to a minus number, you get to move the camera wherever you want!
Perfect for shots like this. I used After Effects to draw a line around the navigable space, as the arena is a little hard to read from the image alone.
“Noclip” is another classic. This one lets you walk through walls (which is why Danny O’Dwyer’s channel name is so smart - the show takes you to places you don’t normally get to see!), which was handy for entering the arena without the monsters spawning, so I could catalogue the placement of all the items.
I used a few others, too. When the Baron of Hell spawns in, he does an awesome roar animation but it’s incredibly quick. I used “ai_animationspeed” to slow all the demons down, allowing me to capture that roar at a sensible speed.
Some stuff seemed beyond the abilities of the console (though, with over 4000 commands I might have missed a few!). I couldn’t lower my weapon (but it’s hidden in photo mode, so no big deal). I couldn't hide all the detritus on the map screen (so I recreated it in Photoshop). And I couldn’t hide the HUD on the collectibles screen - so I removed it manually with some careful zooming and masking.
I find all of this stuff really fun, and I think it gives GMTK an edge over other video essays. Instead of chucking in random clips of playing the game, I spend a lot of time as a cinematographer, actually going out and “shooting” the game - to get the exact clips I want and with a good angle, lighting, and without messy HUD stuff. I hope you appreciate it!
Chat soon, thank you, stay safe.
Mark
Comments
Dominik Bartsch
Thanks that you put our conversation in discord into this blog post!! :)
Glen Ford
+1 to what Solomon and Steven said.
