[FrameGraph] Improve high level rendering usages

[T-rvw]

1.A resource manager holds every resource handles in bgfx. Any renderers can use string to find the expected one. 2.As RenderGraph talk said, I need to split resource compile stage away from render logic!

[T-rvw]

The first step was done easily by adding StringHash support and moving resource creation apis to RenderContext. FrameGraph / RenderGraph is on the way!

[T-rvw]

• Posts except the source talk in GDC.
  • Machinery Post : https://ruby0x1.github.io/machinery_blog_archive/post/high-level-rendering-using-render-graphs/index.html
  • Ubi DX12 Talk : https://www.gdcvault.com/play/1024656/Advanced-Graphics-Tech-Moving-to

[T-rvw]

• Reference Projects
  • https://github.com/acdemiralp/fg
  • https://github.com/Themaister/Granite
  • https://github.com/skaarj1989/FrameGraph-Example

[T-rvw]

Current understanding to implement Render Graph on top of bgfx. The requirement is:

• Manage transient or other kinds of Resources Lifetime.
• Convert RTV and SRV automatically if need to blit.
• Input Effects, Passes, Resource Dependencies and output sorted passes in high performance.
• Submit structed/uniform buffers automatically.
• Support multiple rendering pipelines.
• [Optional] Insert Fence/Barrier to reasonable positions. But it is only for modern backends.