Add Vulkan/Metal rendering support

[kblaschke]

Currently, libprojectM only supports rendering using OpenGL 3 and GLES 2. Since OpenGL is generally considered a deprecated API and Vulkan/Metal has a better API to perform multi-threaded rendering and shader compilation, it will be a good step forward to add support for these next-gen rendering APIs.

Any API-specific initialization calls, e.g. providing the required Vulkan structs, should be implemented in a specific header, e.g. libprojectM/renderer_vulkan.h. Adding support for multiple rendering backends will also require a major refactoring of the library, abstracting rendering-related calls. projectM only renders a few primitives (triangle fans/strips, line strips and points) and uses vertex and fragment shader programs, so there's not much to implement.

Line rendering should be improved beforehand, as covered by issue #682.

Vulkan support should be introduced together with the EGL migration covered by issue #681.

[olilarkin]

You could also consider sticking to GLES and using libangle to translate it to Metal (could even be used on windows so it works on top of direct 3D etc)

[olilarkin]

Just thought I'd mention it since I've had some recent success with the metal port of angle

[kblaschke]

GLES is very limited, and also doesn't allow proper multithreading. Using Vulkan/Metal directly would give some performance improvements, especially when switching presets, as shaders and other resources could be set up in a dedicated parallel thread instead of the render thread, which currently causes hiccups.

[jherico]

is any work being done on this currently or is it up for grabs?

[revmischa]

is any work being done on this currently or is it up for grabs?

No work is being done, please feel free!

[kblaschke]

is any work being done on this currently or is it up for grabs?

Anyone who wants to do this, please go ahead!

If you're implementing it, please keep OpenGL/GLES support in projectM. While OpenGL is deprecated, it's still the only way to get projectM running on some devices and systems, one of them being WebGL/Emscripten.

Also note libprojectM is a library, so all render system initialization should not be part of the library, but done in the outside application. Whatever is needed to render output (e.g. the Vulkan device & swapchain information) needs to be passed in via the API.