Merge branch 'feature/readme' into 'develop'

Update readme

See merge request !22

README.md

-<a href="https://git.io/liblava"><img align="left" src="https://github.com/liblava.png" width="200" style="margin:0px 40px 0px 0px"></a>
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-🌋 **[liblava](https://git.io/liblava) &nbsp; A modern and easy-to-use library for the <a href="https://www.khronos.org/vulkan/" target="_blank">Vulkan</a>® API**
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-**lava** is a lean framework that provides **essentials** for **low-level graphics**<br />and is specially well suited for **prototyping**, **tooling** and **education**
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-<br />
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-**C++20** &nbsp; + &nbsp; **Modular** &nbsp; / &nbsp; **Windows** &nbsp; + &nbsp; **Linux** &nbsp; / &nbsp; **[Demos](#demos)** &nbsp; + &nbsp; **[Projects](#projects)**
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-[![Version](https://img.shields.io/badge/Version-0.6.2-blue)](https://git.io/liblava) [![License](https://img.shields.io/github/license/liblava/liblava)](LICENSE) [![CodeFactor](https://www.codefactor.io/repository/github/liblava/liblava/badge)](https://www.codefactor.io/repository/github/liblava/liblava) [![Discord](https://img.shields.io/discord/439508141722435595)](https://discord.lava-block.com) [![Donate](https://img.shields.io/badge/Donate-PayPal-green.svg)](https://paypal.me/liblava) [![Twitter URL](https://img.shields.io/twitter/url/http/shields.io.svg?style=social&label=Follow)](https://twitter.com/liblava)
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-<br />
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-### [Features](doc/Features.md)
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-* written in **modern C++** with latest **Vulkan** support
-* **run loop** abstraction for **window** and **input** handling
-* plain **renderer** and **command buffer** model
-* **texture** and **mesh** loading from virtual **file system**
-* **GUI** + **camera** + **logging** + **utils** and much more
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-<br />
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-##### ➜ Download latest **<a href="https://github.com/liblava/liblava/releases/latest">demo</a>** (December 20, 2020)
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-<br />
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-<a href="https://www.khronos.org/vulkan/" target="_blank"><img align="right" hspace="20" src="res/Vulkan_170px_Dec16.png" width="300"></a>
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-[Requirements](#requirements) &nbsp; [Build](#build) &nbsp; [Template](#template)
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-<br />
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-### Docs
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- **[Tutorial](doc/Tutorial.md)** &nbsp; [Guide](doc/Guide.md) &nbsp; [Reference](doc/Reference.md) &nbsp; [Tests](doc/Tests.md) &nbsp; [Third-Party](doc/Third-Party.md) &nbsp; [Install](doc/Install.md)
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-<br />
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-### [Modules](doc/Modules.md)
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-[![core](https://img.shields.io/badge/lava-core-blue.svg)](liblava/core) [![util](https://img.shields.io/badge/lava-util-blue.svg)](liblava/util) [![file](https://img.shields.io/badge/lava-file-blue.svg)](liblava/file) &nbsp; [![base](https://img.shields.io/badge/lava-base-orange.svg)](liblava/base) [![resource](https://img.shields.io/badge/lava-resource-orange.svg)](liblava/resource) [![asset](https://img.shields.io/badge/lava-asset-orange.svg)](liblava/asset) &nbsp; [![frame](https://img.shields.io/badge/lava-frame-red.svg)](liblava/frame) [![block](https://img.shields.io/badge/lava-block-red.svg)](liblava/block) &nbsp; [![app](https://img.shields.io/badge/lava-app-brightgreen.svg)](liblava/app) [![demo](https://img.shields.io/badge/lava-demo-brightgreen.svg)](liblava-demo)
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-<br />
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-### Demos
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-##### [lava spawn](liblava-demo/spawn.cpp) ➜ uniform buffer camera
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-<a href="liblava-demo/spawn.cpp">![spawn](res/spawn/screenshot.png)</a>
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-<br />
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-##### [lava lamp](liblava-demo/lamp.cpp) ➜ push constants to shader
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-<a href="liblava-demo/lamp.cpp">![lamp](res/lamp/screenshot.png)</a>
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-<br />
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-##### [lava triangle](liblava-demo/triangle.cpp) ➜ classic colored mesh
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-<a href="liblava-demo/triangle.cpp">![triangle](res/triangle/screenshot.png)</a>
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-<br />
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-### Projects
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-##### [raytracing cubes](https://github.com/pezcode/lava-rt/blob/main/demo/cubes.cpp) ➜ raytraced reflecting cubes ([pezcode/lava-rt](https://github.com/pezcode/lava-rt))
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-<a href="https://github.com/pezcode/lava-rt/blob/main/demo/cubes.cpp">![cubes](https://raw.githubusercontent.com/pezcode/lava-rt/main/demo/res/cubes/screenshot.png)</a>
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-<br />
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-## Requirements
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-* **C++20** compatible compiler
-* CMake **3.20+**
-* [Vulkan SDK](https://vulkan.lunarg.com)
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-<br />
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-## Build
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-[![Build status](https://ci.appveyor.com/api/projects/status/gxvjpo73qf637hy3?svg=true)](https://ci.appveyor.com/project/TheLavaBlock/liblava) [![Build Status](https://travis-ci.com/liblava/liblava.svg?branch=master)](https://travis-ci.com/liblava/liblava)
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-```bash
-git clone https://github.com/liblava/liblava.git
-cd liblava
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-git submodule update --init --recursive
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-mkdir build
-cd build
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-cmake ..
-make
-```
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-<br />
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-## Template
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-You can start coding with the **template** project. If you like you can rename it in [CMakeLists](CMakeLists.txt)
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-➜ Just put your code in the [src](src) folder. Everything you need is in [main.cpp](src/main.cpp)
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-<br />
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-## Collaborate
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-Use the [issue tracker](https://github.com/liblava/liblava/issues) to report any bug or compatibility issue
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-:heart: Thanks to all **[contributors](https://github.com/liblava/liblava/graphs/contributors)** making **liblava** flow...
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-<br />
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-### Support
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-If you want to contribute, we suggest the following:
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-1. Fork the [official repository](https://github.com/liblava/liblava/fork)
-2. Apply your changes to your fork
-3. Submit a [pull request](https://github.com/liblava/liblava/pulls) describing the changes you have made
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-<br />
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-## License
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-<a href="https://opensource.org" target="_blank"><img align="right" width="90" src="http://opensource.org/trademarks/opensource/OSI-Approved-License-100x137.png" style="margin:0px 0px 0px 80px"></a>
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-**liblava** is licensed under [MIT License](LICENSE.md) which allows you to use the software for any purpose you might like, including commercial and for-profit use!
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-<br />
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-However, this library includes several [Third-Party](doc/Third-Party.md) libraries, which are licensed under their own respective **Open Source** licenses ➜ They all allow static linking with closed source software
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-**All copies of liblava must include a copy of the MIT License terms and the copyright notice**
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-##### Vulkan and the Vulkan logo are trademarks of the <a href="http://www.khronos.org" target="_blank">Khronos Group Inc.</a>
-##### Copyright (c) 2018-present, <a href="https://lava-block.com">Lava Block OÜ</a> and [contributors](https://github.com/liblava/liblava/graphs/contributors)
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-<br />
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-<a href="https://git.io/liblava"><img src="https://github.com/liblava.png" width="50"></a>
+# Virtual Reality Rendering Framework
+This framework is based on [liblava](https://github.com/liblava/liblava) and was extended to include features necessary for developing and evaluating new stereo rendering strategies.
+A special focus of the framework lies on remote rendering for standalone consumer HMDs over WiFi.
+
+In order to support multiple APIs as well as local and remote rendering a [Headset interface](src/headset/headset.hpp) was introduced with implementations for
+* [OpenXR Headset](src/headset/openxr_headset.hpp), which uses the [OpenXR standard](https://www.khronos.org/openxr/) developed by Khronos to communicate with an HMD.
+* [OpenVR Headset (legacy)](src/headset/openvr_headset.hpp), which uses the [OpenVR API](https://github.com/ValveSoftware/openvr) developed by Valve to communicate with HMDs via the SteamVR platform.
+* [Remote Headset](src/headset/remote_headset.hpp), which uses custom protocol to communicate with a standalone HMD running a [custom application](https://git-ce.rwth-aachen.de/vr-vis/VR-Group/hmd-streaming). 
+* [Emulated Headset](src/headset/emulated_headset.hpp), which is a fallback solution to test out the rendering techniques without the need to having an actual HMD attached.
+
+## Rendering
+This framework is intended to investiage different stereo rendering strategies. 
+Thus, a [stereo strategy interface](src/strategy/stereo_strategy.hpp) was created to easiliy switch between different strategies and compare them.
+Currently, there exist the following stereo strategies:
+* [Naive Stereo Forward](src/strategy/native_stereo_forward.hpp): renders the image for one eye at a time using forward shading.
+* [Naive Stereo Deferred](src/strategy/native_stereo_deferred.hpp): renders the image for one eye at a time using deferred shading.
+* [Multi View Stereo](src/strategy/native_stereo_deferred.hpp): renders both images simulatenously using multi-view.
+* [Depth Peeling Reprojection](src/strategy/depth_peeling_reprojection.hpp): a custom rendering technique desribed below.
+
+In general, the framework supports [shadow mapping](src/utility/shadow_cache.hpp) and approximate global illumination using [light propagation volumes](src/utility/indirect_cache.hpp).
+For evaluation of the performance and quality of the different rendering techniques the framework provides utility functions for [measuring gpu times](src/utility/pass_timer.hpp) and [capturing images](src/utility/frame_capture.hpp) for an external comparison to a ground truth.
+
+## Depth Peeling Reprojection
+Depth Peeling Reprojection is a rendering technique that aims to reduce the duplicate shading that occurs when rendering images for the left and right eye in virtual reality applications.
+Instead of rendering the scene from two perspectives, it will render the first two layers from a single perspective similar to [Mara et. al, Deep G-Buffers for Stable Global Illumination Approximation](https://research.nvidia.com/publication/2016-06_deep-g-buffers-stable-global-illumination-approximation).
+The goal of this approach is to have more information available when reprojecting the resulting images and, thus, having less artifacts due to disoccluded regions.
+Especially when considering streaming the result wirelessly to remote clients it is critical to have reprojection strategies that can handle lost or delayed frames nicely.