Lessons learned from RENOIR - GAME ACCESS ‘16

@grip_digital
facebook.com/gripdigital
Lessons learned from RENOIR
Martin Pernica | @martindeveloper

@grip_digital
Who am I?
• Martin Pernica
• @martindeveloper
• Team leader at Grip Digital
• Rendering
• Physics
• GPGPU

@grip_digital
Outline
• The story
• Recording system
• Light rendering
• Collisions
• Sprites
• Cloth simulation
• Questions

@grip_digital
The story

@grip_digital
The story
• Engine for mixed 2D and 3D
• Great rendering
• Powerful physics
• Easy to use
• Heavily modifiable

@grip_digital
Recording system

@grip_digital
Recording system
• What is “recording system”?
• Small explanation video

@grip_digital

@grip_digital
Recording system
• We have to record every move of the player
• And not just the movement, but physics of other objects
• Sounds easy? Not exactly…

@grip_digital
Recording system
• After many iterations we created the “OK” solution
• There were still pitfalls which have to be solved after
adding the new gameplay features
• And also optimizations are crucial

@grip_digital
Recording system
• Let's start with first naive approach
• Just record positions in world at every frame
• And just “put” the character to exact location every frame

@grip_digital
Recording system
• You may already see “holes” in this solution
• But it was “bad enough” to start prototyping (without
physics related objects)

@grip_digital
Recording system
• The requirements started to grow
• Fluid physics
• Exact time
• Exact position
• Exact collision and light occlusion
• And yes - FPS independent

@grip_digital
Recording system
• We started recording of the movement vectors
• With action types, directions, inputs, times…

@grip_digital
Recording system
struct FRecordTimelineEntry
- bIsValid
- ActionType
- StartLocation
- MoveInput
struct FMoveInputContainter
- Direction
- InputList
- TimeSpentInCurrentState struct FMovementChunk
- Value
- EndLocation
- Duration

@grip_digital
Recording system
• Still not the best solution
• But it worked with varying frame-rate
• It worked with physic enabled objects
• So it was good enough to move in development

@grip_digital
And lesson from
this?
Never over engineer the code (even if its the main gameplay
mechanics), try to achieve first prototype and iterate.

@grip_digital
Light rendering

@grip_digital
Light rendering
• Noir atmosphere needs a great lighting
• UE4 lighting system is really strong
• And you can create breath-taking scenes with it

@grip_digital
Light rendering
• We had two types of lights
• Not interactive
• Interactive

@grip_digital
Light rendering
• Non interactive lights were just illusion in the
background or some other places
• Just “sprites” with emissive material
• Covered with bloom and grain post FX

@grip_digital
Light rendering
• The interactive lights are those lights which affect
player, ghosts and other actors in the game
• It's not easy to use 3D lights on 2D scene
• But we needed one specific type of the light…

@grip_digital
Light rendering
• Volumetric lights
• Real volumetric lights are expensive to render
• For the first prototypes we needed just “OK” looking lights

@grip_digital
Light rendering
• So we started to faking them little bit
• Increase intensity, create wider shape and just move it near to
the wall which creates the “volumetric shape effect”

@grip_digital
Light rendering
• Simple, not good, solution for prototyping
• But what next?

@grip_digital
Light rendering
• After that we just created cylinders for lights
• With good looking material
• To show some moving dust
• And increase the “depth” of a scene

@grip_digital
Light rendering
• But this solution wasn't still good for next part of the game
• We had to create the volumetric lights which can cast nice
shadows
• Why? Occluding lights and shadows are part of the game
mechanic

@grip_digital
Light rendering
• We had to construct those volumetric
meshes at the runtime
• Using ray-casting to detect objects in
front of the light
• And create approx. shape of the light

@grip_digital
Light rendering
• First solution was on CPU with some batching and caching
• Second solution was on GPU using geometry shaders

@grip_digital
Light rendering
• To increase “real” feeling from the
scenes
• We had to create normal maps
• Those normal maps were not correct
compared to the real world
• We just needed normal maps which
will create nice effect in 2D world

@grip_digital
Collisions with light

@grip_digital
Light collisions
• James and ghosts don't like the light
• We have to be able detect when object is lit or not

@grip_digital
Light collisions
• Easy to say, not easy to implement
• Deferred rendering in UE4 works really great, but for this is
not the best
• Because when you are drawing an object you still don't
know if you are lit or not (lights are applied as “post FX”)

@grip_digital
Light collisions
• First naive approach was to use just ray-casting
• It was OK for first prototypes but we knew this is not
the best/last solution

@grip_digital
Light collisions
• Second solution was to create simplified shape and push it
into PhysX world
• After that just detect collisions between objects
• Worked OK until we had to occlude the light and cast
shadows

@grip_digital
Light collisions
• The last solution, which was “work in progress”, was to create
special Light Tagging Render Target
• In shader we read the light buffer, normal buffer and others

@grip_digital
Light collisions
• Some data are pushed into the GPU from the CPU memory, like
locations of characters (mapped to 2D canvas of the screen) and
others (with unique IDs)
• Shader writes lights IDs, detects when is actor inside the light
and write actor ID into the RT
• And CPU will read back those informations (separated thread, in
specific intervals or at some events)

@grip_digital
Light collisions
• Sounds like an expensive solution, but it was good on “better
machines”
• Also we were experimenting with compute shaders to do some
heavy lifting instead of CPU

@grip_digital
Sprites

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Sprites
• At the time UE4 doesn't had a Paper2D plugin
• So we decided to create our custom sprites

@grip_digital
Sprites
• It was easy but we had to split logic into editor and runtime
• We created meshes (shared) in editor for texture, with specific
material which had an support for various effects

@grip_digital
Sprites
• Also we had to modify the UE4 static lighting system
• Because we like to have “light baked” our meshes also

@grip_digital
Sprites
• Also workflow had to be simple
• Artist just had to “throw” texture inside the editor
• And we had to create mesh and everything around
automatically

@grip_digital
Sprites
• After Paper2D came we decided not to throw everything out
• We just used some parts of the Paper2D for our stuff like
• Sprite editor
• Flipbook
• Sprite packing/atlasing

@grip_digital
Cloth simulation

@grip_digital
Cloth simulation
• Every noir detective have to have a coat, right?
• And this coat must be perfect, look perfect and feel perfect
• Because player will look at this character most of the time

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Cloth simulation
• We utilized the NVIDIA APEX support in UE4
• The workflow was really easy
• … but sometimes some features behaved “weirdly”

@grip_digital
Cloth simulation
• We “painted” cloth informations inside
the APEX Cloth tool

@grip_digital
Cloth simulation
• Also we created blocking volumes to not
penetrate the coat into the body :)

@grip_digital
Cloth simulation
• Painting and creating blocking volumes was easy
• But most time consuming was to fine tune every
single vertex to behave exactly as we wanted
• Also we have still “nightmares” when we started using
APEX Cloth with skeletal animations

@grip_digital
Cloth simulation
• But APEX wasn't only used on James' coat
• For example curtains were APEX cloth also

@grip_digital
Small things
• There was a lot small things
• Some of them were visible
• Some of them not, but they did the magic :)

@grip_digital
Conclusion
• Our vision was to iterate really quickly
• Also we wanted to create “breath-taking” visual
• Combined with interesting mechanics and puzzles
• And Unreal Engine 4 did a great job and it was perfect choice

@grip_digital
Q&A

@grip_digital
Thank you for your attention!
• …and enjoy your stay at this great conference!

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