common-shaders
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libretro
Shader for PPSSPP's Hybrid Method
The Hybrid method from PPSSPP combines the sharp color transitions from xbr with smooth gradiants.
The algorithm is as follows:
- determine a feature mask C based on a sobel-ish filter + splatting, and upscale that mask bilinearly
- generate 2 scaled images: A - using Bilinear filtering, B - using xBRZ
- output = A_C + B_(1-C)
Step 1) and 3) needs a shader file to create the Hybrid look. For 2) xBR/ Super xBR / or any other filter can be used.
PPSSPP Source Header: https://github.com/hrydgard/ppsspp/blob/c2f4fad56aada331bbd8dd7db99037285bab853f/GPU/Common/TextureScalerCommon.h
PPSSPP Source CPP: https://github.com/hrydgard/ppsspp/blob/c2f4fad56aada331bbd8dd7db99037285bab853f/GPU/Common/TextureScalerCommon.cpp
There is also a blog entry about the technique. http://blog.metaclassofnil.com/?tag=textures http://blog.metaclassofnil.com/?p=306
Some Screeshots: http://i.imgur.com/24xh3tG.png http://i.imgur.com/gPAwj5m.png http://i.imgur.com/2ve8nXM.png http://i.imgur.com/c5VXbI8.png
http://abload.de/img/gedosatotexzmo3e.jpg
The posterisation effect of xbr is very reduced. Monster Hunter Portable is one of the best examples. However I don't find screenshots for that. So I have to take some of my own.
Hmm this isn't really possible in the shader pipeline. Our shaders apply post-processing to the finished output.
What you want is specific to the emulator and what it actually does is apply post-processing to the textures before applying them to the final output.
I don't want texture filtering within the shader pipeline. I would like to have the 'hybrid' method to filter the final image output as a shader (post-processing effect). Means to filter the final complete picture with the hybrid shader. The post processing effect shall follow the algorithm which I posted in the initial message.
As an example: In case of a 2D game, PPSSPP and the Retroarch Hybrid Filter should lead to the same result. In case of a 3D game, PPSSPP will only filter the textures but the the Retroarch Hybrid Filter will filter the complete image.
Unfortunately I only have examples from 3D games. I guess this was a little bit confusing.
Now I understand your post. :)
The limitation in retroarch is the iterative approach. So you can only apply a certain processing on the final picture, which will be the input for the next stage. Means: Image 1 -> Processing (e.g. Bilinear) -> Image 2 - > Processing (e.g. SmartBlur) -> Image 3
However this filter needs a complex algorithm. Means: Image 1 -> Processing (Bilinear) -> Storage of Result 1 Image 1 -> Processing (xBR) -> Storage of Result 2 Image 1 -> Processing (Sobel) -> Storage of Result 3 Image 2 = Result 1 x Result 3 + Result 2 (1 - Result 3)
Maybe a recursive approach could be helpful in general for the future. This would allow much complex filters.
RetroArch is capable of referencing previous passes. We also already have a variety of upscalers and even some edge-detection shaders. It should just be a matter of running each one in a pass and then making a pass that says "if it was an edge, show the xbr result; if not, show bilinear (or whatever)". I'll try to take a stab at it soon.
Alright, I got something worked up in slang but I can port it to Cg pretty easily if it does what you're looking for. I based it on sabr instead of xbr because I already had a single-pass slang version of sabr handy but I can base on whatever in Cg: sabr alone: http://i.imgur.com/wfXoV4X.png sabr-hybrid-deposterize: http://i.imgur.com/IXVOz5C.png
Wow this looks awesome. Especially the skin texture looks great. I hope slang will replace cg soon. But for now cg is still the reference. So it would be great if you could port it to cg.
Thank you so much.