Shader Startup is a small utility mod made for modpacks.
When someone launches the pack for the first time, they get a quick screen asking if they want shaders on or off, with a little before/after preview so they can see the difference. It turns on Iris (or Oculus on Forge) with whatever shader pack is included.
You can swap the preview images for your own by dropping an off.png and on.png into config/ShaderStartup/image.
Shader Startup Team
