The RenderTick Event is fired for every render tick on the client.

You will need to cast the event in the function header as this class:
crafttweaker.event.RenderTickEvent
You can, of course, also import the class before and use that name then.

WorldTick Events implement the following interfaces and are able to call all of their methods/getters/setters as well:

• ITickEvent

The following additional information can be retrieved from the event:

ZenGetter	Return Type
ZenGetter renderTickTime	Return Type float