Patai Gergely cobbpg

Unity hotswapping notes

Unity has built-in support for hotswapping, which is a huge productivity booster. This feature works not only with graphics assets like bitmaps and meshes, but also with code: if you edit the source and save it, the editor will save the state of the running game, compile and load the new code, then load the saved state and continue where it left off. Unfortunately, this feature is very easy to break, and most available 3rd party plugins have little regard for it.

It looks like there’s a lot of confusion about hotswapping in Unity, and many developers are not even aware of its existence – which is no wonder if their only experience is seeing lots of errors on the console when they forget to stop the game before recompiling... This document is an attempt to clear up some of this confusion.

Nota bene, I’m not a Unity developer, so everything below is based on blog posts and experimentation. Corrections are most welcome!


	clear = FrameBuffer $ (DepthImage @1 1000, ColorImage @1 navy) -- ...

	triangleRasterCtx = TriangleCtx CullNone PolygonFill NoOffset LastVertex
	colorFragmentCtx = AccumulationContext (DepthOp Less True, ColorOp NoBlending (V4 True True True True))

	rasterizeWith = Rasterize
	triangles = triangleRasterCtx

	cubeVertexStream = Fetch "stream4" Triangles (Attribute "position4" :: Vec 4 Float)

	{-# LANGUAGE Arrows #-}

	import Control.Arrow
	import Control.Category
	import Prelude hiding (id, (.))

	-- Only for testing
	import Text.Printf

	newtype SF a b = SF (Float -> a -> (SF a b, b))

Patai Gergely cobbpg

Unity hotswapping notes

The basic flow of hotswapping