Precomputed Global Illumination for Games

Game Development Practical SS18

Timothy Blut | 334609 | timothy.blut@rwth-aachen.de

Project Details

• Main goal: Precompute diffuse and specular global illumination for use in realtime rendering.
• Shading model from Epic Games (Lambert for diffuse and GGX for specular)
  • With support for albedo, roughness and normal maps
• Forward PBR pipeline with HDR, filmic tone mapping, bloom, PCF shadows, dithering and FXAA
• glTF scene importer (allows Metallic/Roughness material setup)
• Indirect diffuse lighting is solved using irradiance maps (light maps)
  • Uses Intel's Embree for efficient ray/scene intersection tests
  • Irradiance for each light map texel is computed using an unidirectional path tracer
  • The path tracer uses importance sampling and supports a background cubemap, and albedo and roughness maps (but no normal maps)
  • To allow proper bilinear filtering without shadow bleeding, each texel that is not part of a triangle is set to the closest irradiance value
  • NOTE: The scene loader expects the light map UVs to be in channel 0 (channel 1 is for albedo/roughness/normal maps)
• Specular reflections are rendered using precomputed parallax corrected reflection probes
  • The probes are placed in a scene manually with the in-app UI
  • During the baking process the reflection maps are prefiltered using the proposed filtering method from Epic Games
  • A voxel grid that contains the three closest probes is used to determine which probes to interpolate
  • AABBs are used for parallax correction and specifying the influence region

Setup

Windows

Set the correct path to Embree 3.1 and add the bin/ directory in the Embree installation directory to the PATH variable. Open the Visual Studio solution and build.

Linux

To build the project open a terminal and run:

mkdir build
cd build
cmake ..
make -j`nproc`

Before starting the application in any way, Embree must be added to the path with source libs/embree-3.1.0.x86_64.linux/embree_vars.sh

Running

To start the application navigate to the bin directory and run, for example, ./BakedGI ./models/test2.glb ./textures/test2.lm ./textures/test2.pd.

To bake a new light map run ./BakedGI ./models/test2.glb -bake somename.lm -irr width height samples_per_pixel.

Library licenses

• tiny_gltf.h : MIT license
• json.hpp : Copyright (c) 2013-2017 Niels Lohmann. MIT license.
• base64 : Copyright (C) 2004-2008 René Nyffenegger
• stb_image.h : v2.08 - public domain image loader - Github link
• stb_image_write.h : v1.09 - public domain image writer - Github link

Textures

All textures are taken from textures.com