Searching a special shader, simulating a vertical Arcade CRT

nedo · 13 February 2017 14:03

Hi there, finaly i understand the shaders a little bit and how they work, in combo with a cool overlay, the curvature, scanlines, it almost look like the real thing, but only for Horizontal games. I still haven’t found a shaders who simulate the vertical scanlines right, the scanlines are allways from left to right, so i plan start to build my own, but maybe someone can point me to a allready availible shaders, so i can study it a bit more? Thanks for any help here!

nedo

hunterk · 13 February 2017 14:06

CRT-Hyllian (single-pass) has a parameter to make vertical scanlines and there’s a variant of crt-pi (only available in GLSL format) that runs them vertically.

If you use the FBA core, it rotates shaders appropriate for vertical games, it’s only the MAME core(s) that don’t for some reason.

nedo · 13 February 2017 20:18

hi hunterk! CRT-Hyllian can do the vertical scanlines! looks good enough, what i need now is the curvature, trying to add the crt-geom.cg but so far without luck, curvature there but scanlines gone

hunterk · 13 February 2017 20:40

You can tack curvature onto shaders but it doesn’t usually look very good. The scanlines produce a lot of moire. Try using this shader instead, which already has nice, antialiased curvature and vertical scanlines:

github.com

libretro/glsl-shaders/blob/master/crt/shaders/crt-pi-vertical.glsl

/*
    crt-pi-vertical - A Raspberry Pi friendly CRT shader.

    For use with portrait mode games on landscape mode screens (or landscape mode games on portrait mode sreens).
 
    Copyright (C) 2015-2016 davej

    This program is free software; you can redistribute it and/or modify it
    under the terms of the GNU General Public License as published by the Free
    Software Foundation; either version 2 of the License, or (at your option)
    any later version.


Notes:

This shader is designed to work well on Raspberry Pi GPUs (i.e. 1080P @ 60Hz on a game with a 4:3 aspect ratio). It pushes the Pi's GPU hard and enabling some features will slow it down so that it is no longer able to match 1080P @ 60Hz. You will need to overclock your Pi to the fastest setting in raspi-config to get the best results from this shader: 'Pi2' for Pi2 and 'Turbo' for original Pi and Pi Zero. Note: Pi2s are slower at running the shader than other Pis, this seems to be down to Pi2s lower maximum memory speed. Pi2s don't quite manage 1080P @ 60Hz - they drop about 1 in 1000 frames. You probably won't notice this, but if you do, try enabling FAKE_GAMMA.

SCANLINES enables scanlines. You'll almost certainly want to use it with MULTISAMPLE to reduce moire effects. SCANLINE_WEIGHT defines how wide scanlines are (it is an inverse value so a higher number = thinner lines). SCANLINE_GAP_BRIGHTNESS defines how dark the gaps between the scan lines are. Darker gaps between scan lines make moire effects more likely.

GAMMA enables gamma correction using the values in INPUT_GAMMA and OUTPUT_GAMMA. FAKE_GAMMA causes it to ignore the values in INPUT_GAMMA and OUTPUT_GAMMA and approximate gamma correction in a way which is faster than true gamma whilst still looking better than having none. You must have GAMMA defined to enable FAKE_GAMMA.

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nedo · 13 February 2017 21:04

thanks for the info hunterk, i allready tried this shader, somehow the scanlines dont look vertical here, hmmm i will do some more tests.