HRE :: Hybrid (Clustered Forward/Deferred) Rendering Engine

HRE is a real-time, Physically based, Clustered renderer built with OpenGL and based on the techniques described on the paper Clustered Deferred and Forward shading by Ola Olsson, Markus Billeter and Ulf Assarsson. The aim of this project is to build a testing framework to showcase deferred and forward graphics techniques (hence the hybrid part) and to examine the strengths of Clustered shading. I wrote a lengthy blog post full of cool animations that can serve as an introduction to efficient rendering algorithms as well as a detailed guide of my implementation of Clustered Shading, so make sure to check it out here!

This algorithm was selected for its two major benefits over traditional deferred/tiled solutions: it allows for more freedom to choose forward or deferred shading paths as desired and is a better long term fit for the modern GPU performance trends. It has already been succesfully implemented in some of the best looking games of the last couple of years, with some notable examples being: DOOM 2016, Just Cause 3 and Detroit: Become Human.

Download

Stable builds can be found on the HRE releases page.

Currently only Windows platforms are supported.

Render Samples

Cluster z slices

Main Features

Rendering

Clustered Forward/Deferred Renderer
Physically Based shading
Image Based Lighting
Metallic workflow
Cook-Torrance specular BRDF (w/ lambert diffuse)
Ambient Occlusion & Emissive mapping
Tangent space normal mapping
HDR/linear lighting
HDR/LDR skyboxes
Exposure based tone mapping
Bloom
Multisample Anti-aliasing (MSAA)
Directional & point light sources
Compute shader based light culling
Alpha tested foliage (sponza atrium)
Directional light dynamic shadow mapping
Static Omnidirectional Shadow Mapping for Point Lights
Forward, Tiled Forward and Deferred rendering implementations
- Located in other branches of the repo. Only clustered rendering is actively being developed.

Engine

OpenGL 4.5+
SDL2 backend
JSON Parsing via Nlohmann: JSON for C++
Model Loading via ASSIMP (OBJ, FBX, gLTF2.0 etc)
Scene contents clearly outlined in JSON file
Multiple image loading paths via stb-image and GLI
Immediate mode GUI for debugging via ImGUI
Fully commented for future referencing
Environment map generation on load for IBL and skyboxes
Free flight camera

Development Timeline & Planned Features

The first development cycle began September 2018 and concluded December 2018 with the inclusion of Image Based Lighting and the release of the first stable version: HRE 0.01 "Aachen". For the next couple of months I'll be tackling the issues outlined in the Projects section beginning with fixes for the remaining non-critical bugs and then moving on to a major re-write of the material system. The following is a a list of the engine features I aim to include over the coming months, it's obviously subject to change and all that stuff.

Update #1: Materials & Shadow Mapping

Full material system re-write to decouple mesh & textures.
Implementing a shadow mapping atlas and automatic shadow map reuse.
Fix some unneccessary STL calls.

Update #2: Deferred / Screen Space Effects

Rewriting screen space fragment shaders as compute shaders
Screen Space Ambient Occlusion
Screen Space Reflections
Temporal AA
Improved Color Grading & Tone Mapping

Update #3: Cluster Optimizations

Large amounts of lights via BVH construction
Advanced environment mapping
View Frustum culling
Compute shader based particles
Include Approaching Zero Driver Overhead (AZDO) principles

I'll be writing accompanying blog posts at the end of each major milestone, outlining the new features and their implementations and any complications I found along the way. Meanwhile, Here's the first post which contains an overview of other traditional rendering algorithms and builds the case for Clustered rendering.

Repository structure

Hybrid Rendering Engine
|-- assets              
|   |-- models              # Meshes and textures
|   |-- scenes              # Scene description files in JSON format
|   |-- shaders             
|   |   |-- computeShaders  # Compute shaders for clustered forward
|   |   |-- OldShaders      # Shaders not currently in use
|   |   `-- currentShaders  # Shaders for the current rendering pipeline
|   `-- skyboxes            # Skyboxes in either cubemap or equirectangular map form
|-- build                   # CMake compile  
|-- include                 # Project header files
|-- libs                    # Check dependencies section for descriptions & links
|   |-- ASSIMP               
|   |-- Dear imgui           
|   |-- Glad 
|   |-- Json c++            
|   |-- GLI 
|   |-- GLM 
|   |-- stb_image 
|   `-- SDL2 
|-- modules                 # CMake lib setup scripts
|-- src                     # C++ implementation files
`-- CMakeLists.txt          # CMake build script

Dependencies

In my previous project, SSGE, I made an effort to reduce the amount of dependencies to a minimum. This time however, the pendulum has swung the other way and I've made no restriction whatsoever (within reason) as to what libraries I could include in the project. I did this because I wanted to get more comfortable with the process of including and working with external libraries in C++.

Here's a list of the libraries currently included in the project:

ASSIMP: Mesh and material loading.
dear imgui,: Immediate Mode GUI.
glad: GL loader-generator.
JSON for Modern C++: Scene description and serialization.
OpenGL Image (GLI): Image loading for DDS files.
OpenGL Mathematics (GLM): Linear algebra / matrix library.
SDL2: Hardware abstraction layer.
stb_image: Image loading/decoding for JPG, PNG, HDR.

Here's a list of the libraries not included:

CMake: Build generation.
OpenGL: All things GPU & graphics.

All included libraries are represented here under their respective licenses which can be found in the links above or in the licenses.txt doc in the libs folder.

References

There's a comprehensive indexed list of references for the project that I keep more or less up to date in this page of the wiki. However, I find myself constantly returning to a subset of them for further reading or when I need inspiration, so I've added links below to share them and spread the word of their awesomeness. Check them out!

Learn OpenGL: OpenGL tutorials and general introduction to 3D graphics concepts.
Parallel Computer Architecture and Programming : Intro to the GPU programming model.
Doom(2016) - Graphics Study: Dissection of a frame in the id Tech 6 engine.
Siggraph2016 - The Devil is in the Details: idTech 666: A behind-the scenes look into the renderer tech of DOOM 2016. Probably the biggest inspiration in terms of features and overall quality level that I'm striving for.
Efficient Real-Time Shading with Many Lights: An introduction to clustered shading directly from the writers of the original paper. Also outlines some practical tips from industry veterans.
Real Shading in Unreal Engine 4: The principles and implementation details behind UE4 physically based shading model. Includes shader code!
Forward vs Deferred vs Forward+ Rendering with DirectX 11: Detailed overview of different rendering algorithms.

Acknowledgements

Models & Textures

Sponza (gLTF2 Version) : Original model: Frank Meinl, First modified by: Morgan McGuire, PBR Textures: Alexandre-pestana.
Barcelona Sunrise (HDR Map): by @Blochi
Battle Damaged Sci-fi Helmet (PBR): by @theblueturtle_
Metal Rough Test Spheres (PBR): by Ed Mackey.
gLTF Sample Model Repository: All other models & textures.
sIBL Archive: All other HDR maps & skyboxes.
Default Skybox

Thank you to all the 3D & texture artists who have made their assets free to use and so beautiful to look at. If it weren't for you guys I'd probably still be staring at the same old boring utah teapot all damn day!

If I've mis-acknowledged, misattributed, or missed any references, please, create a new GitHub issue or send me a DM on Twitter and I'll make sure to fix it immediately.

Graphics Programming Community <3

Shout-out to Kostas Anagnostou and Eric Arnebäck for taking the time to answer all of my questions for the last couple of months, your explanations made understanding every daunting topic so much easier!

License

MIT License

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

corefan / HybridRenderingEngine