Godot Post Processing Manager

Custom post processing in Godot 4 with streamlined process, automated layer creation and effect display in the editor view.

To add custom post processing, just add a new node of type "PostProcessingManager". Manage its resources for effect customization.

To do:

• C# bindings
• Figure out how to make the effects cover entire view in 2D viewport
• Support depth based effects if they are possible?