Notes on a talk by Elan Ruskin of Insomniac
- Slides (PDF)
- Engine began life in Fuse
- Much more open world than they’ve used before (5 km across)
- 154MB of source code (.h and .cpp)
- Frame breakdown
- 33 ms/frame
- GPU renders 1.3333 frames behind the CPU
- Post-processing happens at the start of a frame
- Main thread
- 3 ms streaming asset setup/teardown, initialize/destroy actor
- 10ms update gameplay logic
- 6ms physics and audio
- last 8 ms submit work for render thread
- High priority and low priority worker threads—urgent things like skeletal animation can interrupt them
- GPU 1 1/3 frames behind
- CPU gets 1/3 of the way through the frame when it tells the GPU where everything is
- Gotta keep that geometry around until the GPU is done with the geometry
- GPU is ending its frame when the CPU is starting the next one
- Things not threadsafe in the engine
- Creating actors (a.k.a. entities)
- Creating/removing compoentns
- Creating/removing entities
- Allocating entities
- Components of a given class have to come together (all animation components, all AI, all movers, etc.)—may depend on each other
- Took some things away from the component system (moved back to a big for loop)
- Level of detail
- Turned down tick rate for stuff far away
- Keep on top of this—if no one’s ever going to see it, don’t waste tris
- Simple is good
- City building
- For details on city-building, see “Procedural Generation of Manhattan” talk
- Started with Houdini
- Needed to allow artists to hand-edit it, then feed that data back into Houdini
- Houdini emits “prefabs” as JSON, which can be modified
- Simple text data interchange is super useful for tech artists and custom gameplay system—easy to move between tools
- Hand-editing procedural content is okay, but it’s cyclic and complicated
- Fit the tech to the context!
- Created custom gameplay systems specific to this game
- Streaming
- See talk “Streaming Sunset Overdirve’s Open World”
- 9 tiles loaded at a time (128 m across each)
- Top player speed is 72 mph, and you might have up to 5 tiles loading at a time, but the 3 in front of you on a diagonal are most important
- Thus, tiles have to be ready in 1.33 seconds
- What happens if you have a slow hard drive?
- Came up with budget of 20 MB per tile
- Want a bigger budget? Figure out what assets you can procrastinate on
- Delay the biggest two Mips, and the middle ones
- If you’re moving fast, you can’t tell at all
- New budget: 20 MB up front, plus 20 MB for when you slow down
- Defer detailed ground objects until you both slow down and get close to the ground
- Originally hoped for no load spinners ever (via airlocking and other other dirty tricks like cutscenes designed to be juuust long enough to load all the assets you need
- Takes too long to do this because it’s so damn fancy
- Gave up after only doing a couple of these
- Initially relied heavily on duplicating assets
- Disk: want consistent read size, no seeks
- Had to duplicate assets in various places on disc to do this
- Gave up on this for big asset types to save more space
- Considered trying better compressor than LZ4, but decided against it
- Did improve compression by changing the way they index tris in the models
- Rendering New York
- See Digital Foundry’s “Marvel’s Spider-Man: A complete analysis” video
- What’s not loaded? Have a single low-res version that’s always rendered that gets the better versions mapped over it
- Autogenerated from full-res geometry
- Single shared 4k texture per zone
- Stream a high-res version as you get close
- Water towers, AC units, etc. really affect outline of building, so those always get loaded on top of the buildings (not box-shaped like buildings)
- Created a cheaper version of these that only uses 40 bytes for use far away—no animations, nothing fancy
- 13 MB for the whole city
- Revisit speed-space tradeoffs!
- Photo mode
- Undervalued by programmers
- Original plan: 3D camera, basic controls, some stickers
- Added frames, selfie mode later
- When people were doing this on the team, it sparked a lot of new ideas
- Huge promotional thing for getting social media traction
- Because it was in at day 1, it hit at the peak of their own marketing
- “If there’s no fun then what is even the point?”
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