Anyone have CRT style shaders?

I was really hoping to find some neat CRT type shaders used by all sorts of emulators but I can’t find anything for MonoGame.

Does anyone have something? I saw the bloom effect code but it’s so complicated. I wish for something simple like emus seem to have that just do it with single shader file.


Here’s a good one ported from libretto, originally written by Timothy Lottes:

If you look through the commits you’ll see specific optimizations that may or may not suit your purpose. The biggest win by far is to use 2 for the gamma exponent instead of 2.2. I tried all libretro CRT shaders and thought this was the best one.

Here’s the repo with libretro shaders:
They’re pretty easy to port to HLSL for MG. I recommend trying out the effects with a game to see which ones you like :slight_smile:
I recall writing a script to automate porting over the shaders for MG, if you (or anyone else) is interested in it I’ll look around if I can find it.


Awesome my friend, thank you!

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Hi there,

I never used any shaders before so I´m a newby. When I´m trying to use the crt-lottes-mg.fx-shader I get the error message “maximum temp register index exceeded” for quite a few codelines. For example for this line: return(c<=0.04045)?c/12.92:pow((c+0.055)/1.055,2.4);
And just one other error:
return ToLinear(brightboost * tex2D(DecalSampler,pos.xy).rgb);

Any ideas what might be wrong here?



Try to change ‘ps_4_0_level_9_0’ to ps_4_0_level_9_3’…

Thank you. That erased all the old errors but generated just 1 new error, which is: Compiled shader code uses too many arithmetic instruction slots (945). Max. allowed by the target (ps_2_x) is 512. Consider increasing optimization level to reduce instruction count.
It´s generated on this line:
return float3(ToSrgb1(c.r),ToSrgb1(c.g),ToSrgb1(c.b));
I guess optimizations won´t cut the instrucion slots in half so is there something else I could do?
And I don´t know why it says ps_2_x as I set it to ps_4 and it´s just on opengl on ps_2 and I´m using standard win 10. Even if I change the opengl-stuff to ps_4 it tells me the same error message.



You’ll need ps_4_0 for the Windows build in the commit I linked, I was only testing DesktopGL back then. Note that you’ll need to set the GraphicsProfile to HiDef in Game1 to load the ps_4_0 shader.

Check out the later commits which take away some functionality, but work with ps_4_0_level_9_1 and run faster (timings on my laptop are in the commit messages and can give you an idea of relative performance).

The ps_4_0_level_9_1 and ps_4_0_level_9_3 targets are a bit weird. They are there for DirectX 9 compatibility and are weaker than ps_4_0. For DesktopGL you can always use 3_0, for DX you can use 4_0_level_9_3 for better compatibility or higher (up to 5_0) for more capabilities.

Thanks a lot Jjagg. That works really nice now.

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