Windows renderer: Nearest neighbor video scaling

VelocityRa commented 7 years ago

This PR implements nearest neighbor video filtering/scaling for the Pixel Shader renderer used on Windows.

Description

Nearest neighbor scaling is the conventional scaling used in emulators for older systems, as it results in the most accurate and crisp image. The lack of it was the first thing I noticed when I initially tried RetroPlayer, so I decided to take a crack at it.

It's implemented on Linux, but for windows it was only implemented in the software renderer. DXVA and the Pixel Shader renderer didn't support it. This PR implements it for the Pixel Shader renderer. It's not needed for DXVA (would be pretty hacky anyway; it doesn't seem to allow you to change the scaling), since we'll probably ditch it for RetroPlayer.

For a few implementation details, here's a copy of the main commit message:

I tried to change as few things as possible by using the color shader used in the pixel renderer to do the sampling.
It's all compile-time and the shader gets recompiled when it needs to (if the sampling option changed from/to nearest neigbor, to/from something else).

Motivation and Context

For RetroPlayer, this was without a doubt needed eventually. Low res games were really ugly/smudgy with the default filtering. With nearest neighbor the image looks as crisp as it should.

How Has This Been Tested?

Tested in RetroPlayer by loading a Game Boy emulator and a game. The difference is quite obvious :)

Screenshots (if appropriate):

Before:

After:

(more obvious full-screen)

Types of change

[x] Bug fix (non-breaking change which fixes an issue)
[x] Improvement (non-breaking change which improves existing functionality)
[ ] New feature (non-breaking change which adds functionality)
[ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

[x] My code follows the Code guidelines of this project
[ ] My change requires a change to the documentation, either Doxygen or wiki
[ ] I have updated the documentation accordingly
[x] I have read the CONTRIBUTING document
[ ] I have added tests to cover my change
[ ] All new and existing tests passed

VelocityRa commented 7 years ago

Handled your remarks, capitalized the getColorRange function and moved its implementation to the source file. Btw, the function needed to return

const std::vector<const float>&

for your last remark to compile.

garbear commented 7 years ago

Good job on the update, now the only comment I have left is the use of m_isNearest. Is this because of the extra define when using NN?

VelocityRa commented 7 years ago

I think it's needed because we need to keep this state to detect/compare (Render -> HandleScalerChange) whether a relevant change in the settings has occured. It's indeed possible that we already have this information from someplace else, however. I'll check later to make sure.

VelocityRa commented 7 years ago

Yeah m_isNearest is needed. It's the simplest solution, the alternative (if it even works) would be pretty hacky. Edit: MSVC decided it has problems with const in the vector now. Fixed it.

garbear / xbmc