opengl-upscale-test
Some shaders work well at lower resolutions, but can't sustain smooth framerates at higher resolutions.
This is an attempt to determine whether rendering to a lower-resolution framebuffer then upscaling via blitter is an acceptable fix, both from a performance standpoint (I'm unsure of the overhead of blitting from, say, 960x540 to 3840x2160) and an image-quality standpoint.
Obviously this will also be heavily GPU (and probably CPU/DRAM) dependent, but hey, you work with the tools you have, right?
The shader is the very heavyweight (but very cool) Protean Clouds created by user nimitz on Shadertoy.
It uses OpenTK for convenient .NET OpenGL bindings and my eyecandy library to load/compile the shader files.
Results from my machine (AMD Ryzen9 3900XT, RTX2060, 64GB DDR4-4133):
- Windowed size is 960x540, full-screen is 3840x2160 (4K)
- Direct to OpenGL's backbuffer: windowed averages 186 FPS, full-screen falls to just 12 FPS.
- Full-sized buffering: windowed 183 FPS, full-screen 12 FPS.
- 1024x576 texture, framebuffer blitter upscaling to 4K: 158 FPS.
The 1024x576 buffer dimensions were determined by setting the maximum width 1024 and calculating the height based on the viewport resolution. Note the code won't allocate a buffer that is larger than the current viewport resolution. (The current code would have to be changed to also set GL.Viewport for this to work, but it doesn't make sense to do more work than is required.)
Best of all, the quality was very acceptable, at least for this particular shader.