Ok, so I want to make some custom visual effect appear on the player's screen, such as a fog similar to the nightvision or blindness potions. I managed to trace this effect to the EntityRenderer class, which seems to control things like fog or shader effects. The only problem is that there is almost no way to externally control it, since all of the potion effects that change the screen are built into the class. How can I make an effect appear on the screen? Is there a way to hook into the class, or do I need to make my own renderer, or something else? (To specify what exactly I want to do, I just want to make a colored fog appear on the screen when I have a custom potion active)

Thanks! Was looking through the Forge events but forgot about the client ones.

Also, for fog effect there are a couple specific events:

 

RenderFogEvent

FogColors

FogDensity

 

I give an example of using these events in my events tutorial, look at Example #3 at the bottom of this page: http://jabelarminecraft.blogspot.com/p/minecraft-forge-172-event-handling.html