pp.add

Adds a screen-space post-processing effect to the scene's final image. shader names a .shader asset — a shipped short name (pp.presets lists every one), an identity, a path, a guid, or a scene-authored .shader asset — resolved against @builtin::shaders.post.<name> when nothing else answers to it. Effect parameters are passed alongside the name — every property the shader declares is settable by its own name here, and the declared schema is what the option keys are read against, so a name it does not carry is refused against the set it does. Those same properties can be animated smoothly afterward without re-adding the effect. Every name pp.presets returns is one this call accepts, and its schema is readable at @builtin::shaders.post.<name> before the effect is added. layer picks which composited image the effect grades; naming none takes the one the shader's own space belongs to, so a light shader grades scene — the rendered picture before the UI reaches it, in the scene's own light, where a threshold still finds highlights — and a display shader grades all, the picture fitted to the screen with every widget on it. Returns the effect's name, which later removes or toggles it.