In The Trenches Optimizing UE4 for Intel

Jeff Rous – Intel

Niklas Smedberg – Epic Games

In The Trenches: Optimizing UE4 For Intel

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claimed as the property of others.

Agenda

Rationale

How We Measured

Common Pain Points

Shader Optimizations

Optimizing for DX12

Android x86/x64 Support


claimed as the property of others. 4

Why Work Together?

Benefits all games that use the engine

UE4 runs on more hardware

Intel is 18% GPU share as of last Steam survey

Optimizations help everyone – high end to phone

Common goals

Leading edge APIs like DX12 are going to power tomorrow’s games

Android is a large market and key for Epic and Intel



Intel® HD Graphics: Roadmap

Sandy Bridge

Intel® 2nd Gen Core™ Processor

• 32nm

• Feature Level 10.1

• Up to 12 EUs

2011

Ivy Bridge


• 22nm


• Up to 16EUs

2012

Haswell


• Feature Level 11.1• DX Extensions

• GT3 (40 EUs)• EDRAM• Iris Pro™, Iris™

brands

2013

Broadwell


• 14nm


• Up to 48 EUs

2014

Skylake

Intel® 6th Gen Core™ Processor


• GT4 (72 EUs)• GT3e 15/28W• DX12 HW

2015-16

Up to 30X faster graphics over last 5 years



Intel® HD Graphics: EDRAM

Basic facts

Located on the same package with CPU 64-128MB Bandwidth – 50 GB/Sec each way

(100BGB/sec total BW) Acts as 4th level $ Just works: no API required to use and take

advantage

Bandwidth Saving

Increasing compute requires more bandwidth

EDRAM helps to reduce BW consumption and improve EU efficiency

Just works but efficiency can be improved by re-using frame data

CPU Package

Intel 6rd Gen Core™ chip

CPU Core

CPU Core

CPU Core

Ring-bus

CPUCore

LL

$SystemMemory

Gfx Core

EDRAM



How We Measured – Intel GPA

Use ToggleDrawEvents command

Frame debugging and live mode

Experiment!



How We Measured

ProfileGPU command

Stat commands

Windows Performance Analyzer

Intel Extreme Tuning Utility



Intel Pain Points – Memory Bandwidth

Memory bandwidth is at a premium with integrated graphics

Gbuffers are memory hungry. UE4 is configurable where you can change the format, eliminate, or even combine channels. Scaling the resolution of gbuffersis good to a point.



Intel Pain Points – Dense Geometry

Sub pixel or very dense mesh vertex shader execution can’t be covered by pixel shader execution leading to hardware starving. Use LOD where possible.

Clipper can get bottlenecked in the worst cases. Use frustum culling on bounding boxes at the very least. Occlusion culling for hidden objects.



A Word About Power

Intel graphics typically in low power systems.

Less CPU usage means more graphics.



Shaders – Local Memory

64 byte cache lines benefit from loop unrolling a great deal.

Avoid small loads in tight loops



Shaders – Branching and Sampling

Using lots of temporaries can starve the hardware.

Branching is expensive if the loads are inside the conditional blocks.

Group the loads as early in the shader as possible to help cover latency.



Demo - DX12 In Engine Metrics



DX12 Performance – Fast Clear

Specify optional D3D12_CLEAR_COLOR when calling CreateCommittedResource

Intel hardware has fast clear path for 1 bit per pixel clear values eg. (1,0,1,0)

When clearing, use the up front specified color for maximum performance.

~9% performance gain on Elemental Demo on DX12!

In the engine today



DX12 Performance – Root Signature

Blueprint of resources available

Root constants

Root descriptors

Descriptor tables

Constants that sit directly in root are copied to each invocation of the shader (pushed) rather than read from memory when used (pulled)

Can significantly speed up shader execution

Automatically handled by driver in DX11



Video - GPA Live Metrics on Android



Android x86/x64 Support

Native apps reduce CPU load, startup times and power consumption

Supported in UE4 today through editor menu

Requires source build

Package as fat or separated APKs

Popular toolchains support x86/x64

Intel INDE

Google NDK

Nvidia CodeWorks



OpenGL ES 3.1 + Android Extension Pack

Supported on latest Intel tablets (Acer Predator 8, Lenovo Yoga Tab 3)

Enabled in UE4 for highest end mobile visuals

Runs with deferred renderer

ASTC textures

PC features are now on mobile

Compute shaders

Indirect drawing



And Announcing…Fast ASTC compression

Next gen format (OpenGL ES, Vulkan)

Very good compression on RGB/RGBA for variety of block sizes

UE4 is adding support for Intel’s fast texture compressor for ASTC

44x speed improvement

Quality comparable to ARM compressor

UE4 uses Intel’s BC6H/BC7 compressors already

Aiming for 4.12 release



ASTC Quality Comparison

Zoomed in portion of a 2048x2048 normal map

Original: 12 MB ETC1: 2 MB ASTC 6x6: 1.8 MB



Wrap up

Test on Intel hardware early. UE4 is powerful but you can easily bring down a high end discrete card. With proper optimization UE4 runs really well on Intel hardware.

Take advantage of scaling features in UE4 – Epic has done a lot of work to support lower end hardware.

UE4 is mobile ready – Take advantage of built-in Android x86/x64 and OpenGL ES 3.1 support in your games for better performance and visuals.



Links

Intel Developer Zone (software.intel.com)

Unreal Engine 4 (unrealengine.com)

Intel GPA (software.intel.com/en-us/gpa)

ISPC Texture Compressor sample (software.intel.com/en-us/articles/fast-ispc-texture-compressor-update)

Using Android x86 on UE4 (software.intel.com/en-us/articles/Unreal-Engine-4-with-x86-Support)

Intel Software Occlusion Culling sample (software.intel.com/en-us/articles/software-occlusion-culling)

https://software.intel.com/en-us/gpa



https://software.intel.com/en-us/articles/fast-ispc-texture-compressor-update

https://software.intel.com/en-us/articles/Unreal-Engine-4-with-x86-Support

https://software.intel.com/en-us/articles/software-occlusion-culling

In The Trenches Optimizing UE4 for Intel

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