Rainbow with composite - MOD preset for Sega Genesis Games

Hello there people. I have managed to find a preset that may allow to show off the mythical Rainbow effect from composite connection in Sega Genesis console from early 90s. It’s a little of modding within this preset but still may not look like the final version I’d like to choose.

Just place in main shaders folder.

Some things that would love to add up into this preset modded is:

  1. Somehow make the game to be shown more bright with the same preset OR some additional shader.
  2. Make the rainbow lines being less color saturated, like less visible.

Even though these requirements, I think the effect is quite satisfactory. I’d appreciate any feedback or suggestions or how to meet the requirements from above OR how to combine these options with other composite or CRT or any other shader.

I hope you like this little thing I found, since this is was very crucial effect to complete the composite connection experience and to be exposed with the real Sega Genesis/Megadrive console.

1 Like

A bit further enhanced mod, v2.1:

Some screenshots


rainbow danny mod v2.3, less intense rainbow lines:

1 Like

This is great! I will try it, but right now I’m on OSX where I don’t have access to SLANG, only GLSL.

1 Like

Last 2 versions for now, v2.4 and v2.5 with some further variances. I’d appreciate if you know how to combine this little mod with LUT or make less visible the rainbow lines or any other suggestion to improve this even further with the dithering/composite effect or some other shader.

Have fun

some other picture:


Someone asked for that purpose, and you are yourself. :laughing: I was doing some tests with the Shaders Venon, is achieved quite close but this is wonderful! How nice to remember that time, when technology that limited but creativity was at its maximum expression.


2 new variants:

1 Like

ok these may be for now the last variants for composite-Rainbow effect. Version 2.7 is for flat screen and v2.71 is with some CRT looking. This time both versions have a less visible rainbow effect which may fit way better compared to the original hardware (pictures below). Hopefully if you know how to improve the composite-dithering even further with this preset, I’d be glad to check that out !

Rainbow effect this time, if ever had to bring a rate then I’d say it’s like 95% accurate in comparison to real hardware composite connection. If it’s anything ever to improve the rainbow lines, I’d say yellow-green bars may need to be a bit more mixed up on screen. I couldn’t notice differences between real hardware pictures and genesis core from distance, but only if you approach to the screen so then you can see little differences with the hardware…

Still, I think it’s a very satisfactory (at least for me) result to get the rainbow effect working to this point. Please feel free to improve this preset even further. I hope you enjoy it as much as I wanted to see rainbow effect in PC to deliver fully experience playing with composite connection-looking with those Sega Genesis classic games. Big thanks to the guys who brought us those shader-presets that I took as a base to make this modding. And big thanks to anybody that would like to give a try to this little mod !

Good luck & Have fun !

Link to v2.7 + v2.71:

Some comparison pictures from real hardware Sega Genesis (model 1) VS RetroArch Genesis Plus GX

1 Like

Hi, I tested it, but there is a problem for me, it modifies the colors so that the green becomes blue. At least when testing on BlastEm.

1 Like

That’s the tvout-tweaks TVOUT_RESOLUTION_Q parameter. If you raise it up to around “130.000000”, it should look more normal, color-wise.

The mame_hlsl passes beyond the first 2 aren’t necessary for rainbows, so you can put those 2 passes anywhere the ntsc-adaptive shaders are currently used just by pasting these lines in their place (paths expecting to run from ‘presets’ directory):

shader0 = "../crt/shaders/mame_hlsl/shaders/mame_ntsc_encode.slang"
filter_linear0 = "true"
wrap_mode0 = "clamp_to_border"
mipmap_input0 = "false"
alias0 = "NTSCPass"
float_framebuffer0 = "false"
srgb_framebuffer0 = "false"
scale_type_x0 = "source"
scale_x0 = "1.000000"
scale_type_y0 = "source"
scale_y0 = "1.000000"

shader1 = "../crt/shaders/mame_hlsl/shaders/mame_ntsc_decode.slang"
filter_linear1 = "true"
wrap_mode1 = "clamp_to_border"
mipmap_input1 = "false"
alias1 = "ColorPass"
float_framebuffer1 = "false"
srgb_framebuffer1 = "false"
scale_type_x1 = "source"
scale_x1 = "1.000000"
scale_type_y1 = "source"
scale_y1 = "1.000000"

ntscsignal = "1.000000"
shadowalpha = "0.100000"
avalue = "0.000000"
bvalue = "0.000000"
pvalue = "1.100000"
scantime = "47.700073"
notch_width = "3.450001"
ifreqresponse = "1.750000"
qfreqresponse = "1.450000"

Have you tried using the RF preset within guest-ntsc? This gave me rainbow colours in the waterfall in Sonic 1 and also in the pipes in Sonic 2.

Not at my computer to give screenshots at the moment, but it’s a lot more subtle than your screenshots and doesn’t degrade quality too much (still looks a lot clearer than RF does from my memory!).

1 Like

I have looked up into guest-ntsc presets and this particular option for RF doesn’t seem to give a similar result to the rainbow I was looking for. Still, I’d appreciate the screenshots you just mentioned nor other preset options to look up. Thanks for your reply!

1 Like

I have looked up into guest-ntsc presets and this particular option for RF doesn’t seem to give a similar result to the rainbow I was looking for. Still, I’d appreciate the screenshots you just mentioned nor other preset options to look up. Thanks for your reply!!

1 Like

New 2 variants, now palette colors should be way more accurate to original games but with some changes.

v2.8 has intense rainbow lines for whoever may like to see them more intense and v2.81 is the one with accurate rainbow lines with 95% accuracy (from my perspective) since v2.7.

This is some demostration playthrough with my limited 10 years old computer to check the rainbow effect with composite modded preset. https://www.youtube.com/watch?v=sfGsi85zB4w

1 Like

This is what I meant, it is a slightly modded preset but it should be largely the same just using the RF option. I guess it might not be quite as pronounced.

1 Like

If I saw it correctly, the lines seem to skip other rainbow colors like yellow or green. Even though the RF option may make them a bit clearer but still, doesn’t manage to expose all the rainbow colors as intended.

1 Like

Last versions are v2.9 - v2.10 and v2.11 … Pretty happy with the color tweaking here and there. v2.9 and v2.10 just keep the 95% accuracy (in my opinion) and v2.11 got more intense rainbow banding. I just found it cool to expose with more intensity these artifacts from time to time.


I just noticed that Rainbow effect doesn’t expose properly in BlastEm core, so now with v2.2 and v2.3 new variants you shall see the rainbow being exposed properly.

v2.2 will show off the 95% accurate (in my opinion) rainbow or I’d say it’s even a bit more accurate than actually it is for Genesis Plus GX. So this version have the sort of tiny rainbow lines. This version only have some dithering applied with no side CRT effects.

v2.3 have the same version from v2.2 but with intense rainbow lines if you like to see more clearly this particular effect in-game plus some CRT effects.


I explain this here. The genesis has no video artifact. Doesn’t handle transparency in hardware like the snes… What you are trying to reproduce is due to the use of bad video cabling. The genesis is rvb, and does not have a rainbow effect. Anyway I explain it here. But I respect the choice of the users, if they played like that, the nostalgia will make them prefer the bad video signal.

Explanation of the artifacts on genesis, due to a bad cabling.

1 Like

I played for such a long time with RGB from earlier Sega Genesis emulators like Genecyst, kgen98 and Gens v2.14. Plus in some other seasons with 4xBRz which just enhances the RGB signal (by default in emulators) in my honest opinion … Still, there’s something beautiful about the blurry looking from 90s’ games (for me). What is looking for in this preset is to expose the rainbow effect by composite as much as I could.

I appreciate the link to explain it way better than me.

1 Like