PBR lab

pbrlab-hair.mp4

pbrlab is well-verified(through brute force human verification and debugging) path tracing + PBR shading/rendering implementation in portable C++11.

pbrlab is good for verifying your renderer and PBR shading.

Features

PrincipledBSDF
- with random-walk(brute force) pathtraced subsurface scattering.
  - https://disney-animation.s3.amazonaws.com/uploads/production/publication_asset/153/asset/siggraph2016SSS.pdf
  - https://disney-animation.s3.amazonaws.com/uploads/production/publication_asset/153/asset/siggraph2016SSS.pdf
  - Extending the Disney BRDF to a BSDF with Integrated Subsurface Scattering https://blog.selfshadow.com/publications/s2015-shading-course/
(Principled) Hair BSDF
- Our Hair BSDF is based on Cycles(pbrt-v3) and applies the fix of pbrt-v3 bug https://github.com/mmp/pbrt-v3/pull/256/files
- Implements an improved robe evaluation method https://jo.dreggn.org/path-tracing-in-production/2018/index.html
Cycles and Arnold compatible shading parameters.

Requirements

cmake
C++11 or later compiler
- We recommend to use clang++ since g++ is slow to compile embree-portable
Embree
- embree-portable is added as git submodule.
OpenGL 3.x
- For GUI. CLI build is also available.

Supported platform

Install Dependencies

Ubuntu

Install clang recommended. Install OpenGL dev package(+ X11) required if you want to build GUI.

$ sudo apt install clang cmake
$ sudo apt install libgl1-mesa-dev libglu1-mesa-dev
$ sudo apt install libxrandr-dev libxinerama-dev libxcursor-dev libxi-dev

Optional

$ sudo apt install ccache

Setup

Checkout submodules

$ git submodule update --init --recursive

Building

Visual Studio(2022)

> vcsetup-2022.bat

Or if you using bash(e.g. from Git for Windows)

$ cmd //c vcsetup-2022.bat

Then open solution file at build folder.

VS2019 may work(please modify generator settings in vcsetup-2022.bat)

Linux

$ ./scripts/bootstrap-linux.sh
$ cd cmake-build-relwithdebinfo
$ make

macOS

$ ./scripts/bootstrap-macos.sh
$ cd cmake-build-relwithdebinfo
$ make

Manual cmake invoking(e.g. vscode)

Standard cmake build procedure should work. for exmaple:

$ mkdir build
$ cmake -B build -S . -DCMAKE_BUILD_TYPE=RelWithDebInfo

For ARM target, add -DEMBREE_ARM=1 cmake option recommended(otherwise SSE/AVX compile flags are used)

TODO: provide CMakePresets.json

Built with external Embree(e.g. prebuilt Embree package).

TBB is required to build. (you can install tbb through sudo apt install libtbb-dev on Ubuntu)

Please set the following cmake option. (See an example bootstrap script in scripts/bootstrap-linux-aarch64.sh )

-DPBRLAB_USE_EXTERNAL_EMBREE=On \
-Dembree_DIR=external/embree-4.0.x86_64.linux/lib/cmake/embree-4.0

embree_DIR points to a folder containing embree-config.cmake

Optionally, set path to TBB package if required.

How to run

Run demo scene.

$ pbrlab data/cornellbox_suzanne_lucy.obj

Surface mesh only.

$ pbrtlab input.obj

Hair only(cyhair format. Download here http://www.cemyuksel.com/research/hairmodels/).

$ pbrtlab input.hair

Mesh and Hair.

$ pbrtlab input.obj input.hair

(No xform/scene graph support at the moment)

Model a scene.

Currently pbrlab supports wavefront .obj + .mtl with PBR + SSS extension

https://benhouston3d.com/blog/extended-wavefront-obj-mtl-for-pbr/

or please take a look at tinyobjloader's note: https://github.com/tinyobjloader/tinyobjloader/blob/release/pbr-mtl.md

SSS extension is pbrlab specific.

SSS parameter in Wavefront .mtl

Please see src/material-param.h and AutodeskStandardSurface

https://autodesk.github.io/standard-surface/#closures/subsurfacescattering

for details.

param name	value	description
subsurface	float	Subsurface weight
subsurface_radius	RGB	Subsurface radius(dmfp)
subsurface_color	RGB	Subsurface color

subsurface_scale is not supported(Please premultiply it to subsurface_radius) subsurface_anisotropy is not supported yet.

TODO

FIXME(Need further investigation)

Random walk SSS
- Slightly darker result compared to Cycles' results
Clearcoat -> Clearcoat component is too small

License

pbrlab is licensed under MIT license.

The following files are derived from these;

src/closure/microface-ggx.h: Open Shading Language (3-clause BSD license)
Principled BSDF, Principled Hair BSDF. Based on Cycles' code. Apache 2.0 license.

Third party license

TinyObjLoader : MIT license.
TinyEXR : BSD license.
imgui : MIT license.
ImGuizmo : MIT license.
stb_image, stb_image_write, stb_image_resize : Public domain
glfw3 : zlib/libpng license.
glad : unlicense?
ionicons : MIT license.
Roboto font : Apache 2.0 license.
toml11 : MIT license.
rapidjson : MIT license.
StaticJSON : MIT license.
ghc filesystem : BSD-3 license.
mpark variant : BSD-1 license.
Embree : Apache-2.0
pcg-random : Apache-2.0
pbrt : BSD-2 license.
Cycles : Apache 2.0 license
OpenShadingLanguage : BSD-3 license.
OpenImageIO : BSD-3 license
miniz: MIT license. https://github.com/richgel999/miniz

lighttransport/pbrlab