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https://forums.unrealengine.com/development-discussion/vr-ar-development/1371458-make-maintain-framerate-technical-postmortem-for-robo-recall-and-beyond-by-nick-whiting

RoboRecall_UnderstandingThreadingModel

Ticking is not multithreaded#

  • The Game Thread handles updates for gameplay, animation, physics, networking, etc., and most importantly, Actor ticking.

  • TickGroups control Tick order but do not give parallelism

  • Physics use tasks within the game thread to perform their work

  • AnimGraphs can do parallel evaluation

  • Trick: Can hide some of your tick work by moving Actors to TG_DuringPhysics, shortening your overall Game thread time

  • Rule Of Thumb: Move things that don’t affect velocity or position of Actors, or generate overlap events into TG_DuringPhysics.

A few of the heavier classes that we moved to TG_DuringPhysics in Robo Recall are:

OdinAIManager

OdinSpeechManager

OdinWaveSpawner

OdinPhysicalAudioComponent

OdinGameMode

OdinScoreManager

OdinPopulationManager

RoboRecall_TG_DuringPhysics

Render Thread:#

  • Handles command list generation

  • At top of thread, calculate final hmd pose

  • Then traverse scene and do parallel command generation

Audio Thread:#

  • The main audio thread is analogous to the Render Thread, and interfaces the game thread with the lower level mixing threads.

  • The decoding and source worker tasks decode the audio information, and also do processing like spatialization and HRTF.

  • The audio hardware thread is a platform dependent thread (e.g. XAudio2 on Windows), which consumes the mix.

Debug HMD Performance:#

-emulatestereo

r.setres 2160x1200

r.screenpercentage 140

‘pause’ - pauses game thread and then use ‘show’ command to profile rendering

Use stat physics & stat anim

Forward Renderer

RoboRecall_ForwardRenderer

Can do 70%-90% scale down with MSAA 2x/4x

MSAA + subpixel geometry = bad juju

Specular aliasing is an issue

Give BP compiler hints on inlining functions. Look at KismetMathLibrary.h for details:

// Conditionally inlined

#if KISMET_MATH_INLINE_ENABLED

#include "KismetMathLibrary.inl"

#endif

Game Thread Optimization:

  • Reduce # ticking actors

  • Reduce # colliders

  • Hide work in TG_DuringPhysics

  • Check number of components in scene


Last update: November 14, 2019