three 基础库
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import {
AdditiveBlending,
Color,
LinearFilter,
RGBAFormat,
ShaderMaterial,
UniformsUtils,
WebGLRenderTarget
} from '../../../build/three.module.js';
import { Pass, FullScreenQuad } from '../postprocessing/Pass.js';
import { CopyShader } from '../shaders/CopyShader.js';
/**
*
* Supersample Anti-Aliasing Render Pass
*
* This manual approach to SSAA re-renders the scene ones for each sample with camera jitter and accumulates the results.
*
* References: https://en.wikipedia.org/wiki/Supersampling
*
*/
class SSAARenderPass extends Pass {
constructor( scene, camera, clearColor, clearAlpha ) {
super();
this.scene = scene;
this.camera = camera;
this.sampleLevel = 4; // specified as n, where the number of samples is 2^n, so sampleLevel = 4, is 2^4 samples, 16.
this.unbiased = true;
// as we need to clear the buffer in this pass, clearColor must be set to something, defaults to black.
this.clearColor = ( clearColor !== undefined ) ? clearColor : 0x000000;
this.clearAlpha = ( clearAlpha !== undefined ) ? clearAlpha : 0;
this._oldClearColor = new Color();
if ( CopyShader === undefined ) console.error( 'THREE.SSAARenderPass relies on CopyShader' );
const copyShader = CopyShader;
this.copyUniforms = UniformsUtils.clone( copyShader.uniforms );
this.copyMaterial = new ShaderMaterial( {
uniforms: this.copyUniforms,
vertexShader: copyShader.vertexShader,
fragmentShader: copyShader.fragmentShader,
premultipliedAlpha: true,
transparent: true,
blending: AdditiveBlending,
depthTest: false,
depthWrite: false
} );
this.fsQuad = new FullScreenQuad( this.copyMaterial );
}
dispose() {
if ( this.sampleRenderTarget ) {
this.sampleRenderTarget.dispose();
this.sampleRenderTarget = null;
}
}
setSize( width, height ) {
if ( this.sampleRenderTarget ) this.sampleRenderTarget.setSize( width, height );
}
render( renderer, writeBuffer, readBuffer ) {
if ( ! this.sampleRenderTarget ) {
this.sampleRenderTarget = new WebGLRenderTarget( readBuffer.width, readBuffer.height, { minFilter: LinearFilter, magFilter: LinearFilter, format: RGBAFormat } );
this.sampleRenderTarget.texture.name = 'SSAARenderPass.sample';
}
const jitterOffsets = _JitterVectors[ Math.max( 0, Math.min( this.sampleLevel, 5 ) ) ];
const autoClear = renderer.autoClear;
renderer.autoClear = false;
renderer.getClearColor( this._oldClearColor );
const oldClearAlpha = renderer.getClearAlpha();
const baseSampleWeight = 1.0 / jitterOffsets.length;
const roundingRange = 1 / 32;
this.copyUniforms[ 'tDiffuse' ].value = this.sampleRenderTarget.texture;
const viewOffset = {
fullWidth: readBuffer.width,
fullHeight: readBuffer.height,
offsetX: 0,
offsetY: 0,
width: readBuffer.width,
height: readBuffer.height
};
const originalViewOffset = Object.assign( {}, this.camera.view );
if ( originalViewOffset.enabled ) Object.assign( viewOffset, originalViewOffset );
// render the scene multiple times, each slightly jitter offset from the last and accumulate the results.
for ( let i = 0; i < jitterOffsets.length; i ++ ) {
const jitterOffset = jitterOffsets[ i ];
if ( this.camera.setViewOffset ) {
this.camera.setViewOffset(
viewOffset.fullWidth, viewOffset.fullHeight,
viewOffset.offsetX + jitterOffset[ 0 ] * 0.0625, viewOffset.offsetY + jitterOffset[ 1 ] * 0.0625, // 0.0625 = 1 / 16
viewOffset.width, viewOffset.height
);
}
let sampleWeight = baseSampleWeight;
if ( this.unbiased ) {
// the theory is that equal weights for each sample lead to an accumulation of rounding errors.
// The following equation varies the sampleWeight per sample so that it is uniformly distributed
// across a range of values whose rounding errors cancel each other out.
const uniformCenteredDistribution = ( - 0.5 + ( i + 0.5 ) / jitterOffsets.length );
sampleWeight += roundingRange * uniformCenteredDistribution;
}
this.copyUniforms[ 'opacity' ].value = sampleWeight;
renderer.setClearColor( this.clearColor, this.clearAlpha );
renderer.setRenderTarget( this.sampleRenderTarget );
renderer.clear();
renderer.render( this.scene, this.camera );
renderer.setRenderTarget( this.renderToScreen ? null : writeBuffer );
if ( i === 0 ) {
renderer.setClearColor( 0x000000, 0.0 );
renderer.clear();
}
this.fsQuad.render( renderer );
}
if ( this.camera.setViewOffset && originalViewOffset.enabled ) {
this.camera.setViewOffset(
originalViewOffset.fullWidth, originalViewOffset.fullHeight,
originalViewOffset.offsetX, originalViewOffset.offsetY,
originalViewOffset.width, originalViewOffset.height
);
} else if ( this.camera.clearViewOffset ) {
this.camera.clearViewOffset();
}
renderer.autoClear = autoClear;
renderer.setClearColor( this._oldClearColor, oldClearAlpha );
}
}
// These jitter vectors are specified in integers because it is easier.
// I am assuming a [-8,8) integer grid, but it needs to be mapped onto [-0.5,0.5)
// before being used, thus these integers need to be scaled by 1/16.
//
// Sample patterns reference: https://msdn.microsoft.com/en-us/library/windows/desktop/ff476218%28v=vs.85%29.aspx?f=255&MSPPError=-2147217396
const _JitterVectors = [
[
[ 0, 0 ]
],
[
[ 4, 4 ], [ - 4, - 4 ]
],
[
[ - 2, - 6 ], [ 6, - 2 ], [ - 6, 2 ], [ 2, 6 ]
],
[
[ 1, - 3 ], [ - 1, 3 ], [ 5, 1 ], [ - 3, - 5 ],
[ - 5, 5 ], [ - 7, - 1 ], [ 3, 7 ], [ 7, - 7 ]
],
[
[ 1, 1 ], [ - 1, - 3 ], [ - 3, 2 ], [ 4, - 1 ],
[ - 5, - 2 ], [ 2, 5 ], [ 5, 3 ], [ 3, - 5 ],
[ - 2, 6 ], [ 0, - 7 ], [ - 4, - 6 ], [ - 6, 4 ],
[ - 8, 0 ], [ 7, - 4 ], [ 6, 7 ], [ - 7, - 8 ]
],
[
[ - 4, - 7 ], [ - 7, - 5 ], [ - 3, - 5 ], [ - 5, - 4 ],
[ - 1, - 4 ], [ - 2, - 2 ], [ - 6, - 1 ], [ - 4, 0 ],
[ - 7, 1 ], [ - 1, 2 ], [ - 6, 3 ], [ - 3, 3 ],
[ - 7, 6 ], [ - 3, 6 ], [ - 5, 7 ], [ - 1, 7 ],
[ 5, - 7 ], [ 1, - 6 ], [ 6, - 5 ], [ 4, - 4 ],
[ 2, - 3 ], [ 7, - 2 ], [ 1, - 1 ], [ 4, - 1 ],
[ 2, 1 ], [ 6, 2 ], [ 0, 4 ], [ 4, 4 ],
[ 2, 5 ], [ 7, 5 ], [ 5, 6 ], [ 3, 7 ]
]
];
export { SSAARenderPass };