Used to implement post-processing effects in three.js. The class manages a chain of post-processing passes to produce the final visual result. Post-processing passes are executed in order of their addition/insertion. The last pass is automatically rendered to screen.
			[example:webgl_postprocessing postprocessing]
			[example:webgl_postprocessing_advanced postprocessing advanced]
			[example:webgl_postprocessing_backgrounds postprocessing backgrounds]
			[example:webgl_postprocessing_crossfade postprocessing crossfade]
			[example:webgl_postprocessing_dof postprocessing depth-of-field]
			[example:webgl_postprocessing_dof2 postprocessing depth-of-field 2]
			[example:webgl_postprocessing_fxaa postprocessing fxaa]
			[example:webgl_postprocessing_glitch postprocessing glitch]
			[example:webgl_postprocessing_godrays postprocessing godrays]
			[example:webgl_postprocessing_masking postprocessing masking]
			[example:webgl_postprocessing_nodes postprocessing node material]
			[example:webgl_postprocessing_outline postprocessing outline]
			[example:webgl_postprocessing_pixel postprocessing pixelate]
			[example:webgl_postprocessing_procedural postprocessing procedural]
			[example:webgl_postprocessing_rgb_halftone postprocessing rgb halftone]
			[example:webgl_postprocessing_sao postprocessing sao]
			[example:webgl_postprocessing_smaa postprocessing smaa]
			[example:webgl_postprocessing_sobel postprocessing sobel]
			[example:webgl_postprocessing_ssaa postprocessing ssaa]
			[example:webgl_postprocessing_ssao postprocessing ssao]
			[example:webgl_postprocessing_taa postprocessing taa]
			[example:webgl_postprocessing_unreal_bloom postprocessing unreal bloom]
			[example:webgl_postprocessing_unreal_bloom_selective postprocessing unreal bloom selective]
		
		[page:WebGLRenderer renderer] -- The renderer used to render the scene. 
		[page:WebGLRenderTarget renderTarget] -- (optional) A preconfigured render target internally used by [name].
		
An array representing the (ordered) chain of post-processing passes.
A reference to the internal read buffer. Passes usually read the previous render result from this buffer.
A reference to the internal renderer.
Whether the final pass is rendered to the screen (default framebuffer) or not.
A reference to the internal write buffer. Passes usually write their result into this buffer.
			pass -- The pass to add to the pass chain.
			Adds the given pass to the pass chain.
		
			pass -- The pass to insert into the pass chain.
			index -- Defines the position in the pass chain where the pass should be inserted.
			Inserts the given pass into the pass chain at the given index.
		
			passIndex -- The pass to check.
			Returns true if the pass for the given index is the last enabled pass in the pass chain.
			Used by [name] to determine when a pass should be rendered to screen.
		
			deltaTime -- The delta time value.
			Executes all enabled post-processing passes in order to produce the final frame.
		
			[page:WebGLRenderTarget renderTarget] -- (optional) A preconfigured render target internally used by [name]..
			Resets the internal state of the [name].
		
			pixelRatio -- The device pixel ratio.
			Sets device pixel ratio. This is usually used for HiDPI device to prevent bluring output.
				Thus, the semantic of the method is similar to [page:WebGLRenderer.setPixelRatio]().
		
			width -- The width of the [name].
			height -- The height of the [name].
				Resizes the internal render buffers and passes to (width, height) with device pixel ratio taken into account.
				Thus, the semantic of the method is similar to [page:WebGLRenderer.setSize]().
		
Swaps the internal read/write buffers.
[link:https://github.com/mrdoob/three.js/blob/master/examples/js/postprocessing/EffectComposer.js examples/js/postprocessing/EffectComposer.js]