rendervulkan: Add Anime4K 2x CNN UL upscaling filter

[Et3rnos]

Overview

Added Anime4K 2x CNN UL (Ultra-Large) as a new upscaling filter option for gamescope.

• New CLI option: --filter anime4k
• 2x neural network upscaler optimized for anime/cartoon content, like visual novels and 2D RPG games

Performance

Benchmarked on RTX 3050 Ti (Laptop) against Lossless Scaling's Anime4K UL implementation:

Input Resolution	Gamescope	Lossless Scaling	Improvement
1280×720	6ms (~166 fps)	9ms (~111 fps)	50% faster
800×600	4ms (~250 fps)	Not tested	Not tested

Estimated VRAM usage:

Input Resolution	VRAM
1280×720	~191 MB
800×600	~100 MB

A consistent 50% performance gain achieved by merging 25 original shader passes into 9, reducing redundant texture fetches by writing to 3 output textures per dispatch.

Visual Quality

Output compared against Lossless Scaling (a perfect match). It is correctly implemented, and the quality matches the original Anime4K shader.

Comparison with FSR

The source game was run at 544x416, upscaled to 1920x1080:

FSR:

---

Anime4K:

Related Threads / Motivation

Those threads mentioned interest on Anime4K being added to Gamescope.

#262
#788

Notes

• This is only an implementation of the Ultra Large (UL) shader variant.
• This is a Vulkan compute shader implementation of the original Anime4K shaders (https://github.com/bloc97/Anime4K - MIT licensed)

[malucard]

To run this without crashing, I had to change 2 to 3 in rendervulkan.cpp:915

[Et3rnos]

To run this without crashing, I had to change 2 to 3 in rendervulkan.cpp:915

Thanks for giving it a try, I've now updated that line.