Native code (C++) rendering plugin example for Unity

This sample demonstrates how to render and do other graphics related things from a C++ plugin, via a native plugin interface.

Unity versions:

The plugin itself does very few things:

Demonstrates basic plumbing. How to initialize the graphics API, and how calls from Unity into plugin are made.
Draws a triangle. A single colored rotating triangle in the middle of the screen. For each backend API, this shows bare basics of how to setup vertex data, setup some shaders or render states, and do a draw call.
Changes Unity texture data. Unity side passes a texture into the plugin, and the code changes the pixels of it each frame, with an animated "plasma" pattern. This demonstrates how to work with Texture.GetNativeTexturePtr.
Changes Unity mesh vertex data. Unity side passes a vertex buffer into the plugin, and the code changes the vertices each frame, with an animated "heightfield" pattern. This demonstrates how to work with Mesh.GetNativeVertexBufferPtr.

Native code rendering is implemented for several platforms and graphics APIs:

Windows (D3D11, D3D12, OpenGL, Vulkan)
- Note that Vulkan and DX12 are not compiled in by default
- Vulkan requires Vulkan SDK; enable it by editing #define SUPPORT_VULKAN 0 to 1 under UNITY_WIN clause in PlatformBase.h
- DX12 requires additional header files (see on github or nuget package); enable it by editing #define SUPPORT_D3D12 0 to 1 under UNITY_WIN clause in PlatformBase.h
macOS (Metal, OpenGL)
Linux (OpenGL, Vulkan)
Windows Store aka UWP (D3D11, D3D12)
WebGL (OpenGL ES)
Android (OpenGL ES, Vulkan)
iOS/tvOS (Metal; Simulator is supported if you use unity 2020+ and XCode 11+)
EmbeddedLinux (OpenGL, OpenGL ES , Vulkan)
QNX (OpenGL ES)
...more platforms might be coming soon, we just did not get around to adding project files yet.

Code is organized as follows:

PluginSource is source code & IDE project files for the C++ plugin.
- source: The source code itself. RenderingPlugin.cpp is the main logic, RenderAPI*.* files contain rendering implementations for different APIs.
- projects/VisualStudio2022: Visual Studio 2022 project files for regular Windows plugin
- projects/UWPVisualStudio2022: Visual Studio 2022 project files for Windows Store (UWP) plugin
- projects/Xcode: Apple Xcode project file for Mac OS X plugin, Xcode 10.3 on macOS 10.14 was tested
- projects/GNUMake: Makefile for Linux
- projects/EmbeddedLinux: Windows .bat files to build plugins for different architectures
- projects/QNX: Makefile for Linux requires QNX to be installed and environment variables to be set
UnityProject is the Unity (2023.1.15f1 was tested) project.
- Single scene that contains the plugin sample scene.

Just like with most other samples, the license is MIT/X11.