This is an example of an Iris-exclusive shaderpack, with a fancy error screen if Optifine is in use.
Please do not use this if your shader is actually compatible with Optifine.
Based off XorDev's Default Shaderpack, original README below: You can do whatever you want with this code! Credit is not necessary, but it's always appreciated! You can find more information about shaders in Optfine here: https://github.com/sp614x/optifine/blob/master/OptiFineDoc/doc/shaders.txt