javascript
/
three.js
peilaus alkaen https://github.com/tazdij/three.js.git


			
				
					
						
						
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		<h1>How to use post-processing</h1>

		<p>
			Many three.js applications render their 3D objects directly to the screen. Sometimes, however, you want to apply one or more graphical
			effects like Depth-Of-Field, Bloom, Film Grain or various types of Anti-aliasing. Post-processing is a widely used approach
			to implement such effects. First, the scene is rendered to a render target which represents a buffer in the video card's memory.
			In the next step one or more post-processing passes apply filters and effects to the image buffer before it is eventually rendered to
			the screen.
		</p>
		<p>
			three.js provides a complete post-processing solution via [page:EffectComposer] to implement such a workflow.
		</p>

		<h2>Workflow</h2>

		<p>
			The first step in the process is to import all necessary files from the examples directory. The guide assumes you are using the official
			[link:https://www.npmjs.com/package/three npm package] of three.js. For our basic demo in this guide we need the following files.
		</p>

		<code>
		import { EffectComposer } from 'three/examples/jsm/postprocessing/EffectComposer.js';
		import { RenderPass } from 'three/examples/jsm/postprocessing/RenderPass.js';
		import { GlitchPass } from 'three/examples/jsm/postprocessing/GlitchPass.js';
		</code>

		<p>
			After all files are successfully imported, we can create our composer by passing in an instance of [page:WebGLRenderer].
		</p>

		<code>
		const composer = new EffectComposer( renderer );
		</code>

		<p>
			When using a composer, it's necessary to change the application's animation loop. Instead of calling the render method of
			[page:WebGLRenderer], we now use the respective counterpart of [page:EffectComposer].
		</p>

		<code>
		function animate() {

			requestAnimationFrame( animate );

			composer.render();

		}
		</code>

		<p>
			Our composer is now ready so it's possible to configure the chain of post-processing passes. These passes are responsible for creating
			the final visual output of the application. They are processed in order of their addition/insertion. In our example, the instance of *RenderPass*
			is executed first and then the instance of *GlitchPass*. The last enabled pass in the chain is automatically rendered to the screen. The setup
			of the passes looks like so:
		</p>

		<code>
		const renderPass = new RenderPass( scene, camera );
		composer.addPass( renderPass );

		const glitchPass = new GlitchPass();
		composer.addPass( glitchPass );
		</code>

		<p>
			*RenderPass* is normally placed at the beginning of the chain in order to provide the rendered scene as an input for the next post-processing step. In our case,
			*GlitchPass* is going to use these image data to apply a wild glitch effect. Check out this [link:https://threejs.org/examples/webgl_postprocessing_glitch live example]
			to see it in action.
		</p>

		<h2>Built-in Passes</h2>

		<p>
			You can use a wide range of pre-defined post-processing passes provided by the engine. They are located in the
			[link:https://github.com/mrdoob/three.js/tree/dev/examples/jsm/postprocessing postprocessing] directory.
		</p>

		<h2>Custom Passes</h2>

		<p>
			Sometimes you want to write a custom post-processing shader and include it into the chain of post-processing passes. For this scenario,
			you can utilize *ShaderPass*. After importing the file and your custom shader, you can use the following code to setup the pass.
		</p>

		<code>
		import { ShaderPass } from 'three/examples/jsm/postprocessing/ShaderPass.js';
		import { LuminosityShader } from 'three/examples/jsm/shaders/LuminosityShader.js';

		// later in your init routine

		const luminosityPass = new ShaderPass( LuminosityShader );
		composer.addPass( luminosityPass );
		</code>

		<p>
			The repository provides a file called [link:https://github.com/mrdoob/three.js/blob/master/examples/jsm/shaders/CopyShader.js CopyShader] which is a
			good starting code for your own custom shader. *CopyShader* just copies the image contents of the [page:EffectComposer]'s read buffer
			to its write buffer without applying any effects.
		</p>

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