81 lines
2.0 KiB
JavaScript
81 lines
2.0 KiB
JavaScript
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import {
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Matrix4,
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Mesh,
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MeshBasicMaterial,
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EqualStencilFunc,
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IncrementStencilOp
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} from 'three';
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/**
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* A shadow Mesh that follows a shadow-casting Mesh in the scene, but is confined to a single plane.
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*/
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const _shadowMatrix = new Matrix4();
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class ShadowMesh extends Mesh {
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constructor( mesh ) {
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const shadowMaterial = new MeshBasicMaterial( {
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color: 0x000000,
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transparent: true,
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opacity: 0.6,
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depthWrite: false,
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stencilWrite: true,
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stencilFunc: EqualStencilFunc,
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stencilRef: 0,
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stencilZPass: IncrementStencilOp
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} );
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super( mesh.geometry, shadowMaterial );
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this.isShadowMesh = true;
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this.meshMatrix = mesh.matrixWorld;
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this.frustumCulled = false;
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this.matrixAutoUpdate = false;
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}
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update( plane, lightPosition4D ) {
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// based on https://www.opengl.org/archives/resources/features/StencilTalk/tsld021.htm
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const dot = plane.normal.x * lightPosition4D.x +
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plane.normal.y * lightPosition4D.y +
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plane.normal.z * lightPosition4D.z +
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- plane.constant * lightPosition4D.w;
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const sme = _shadowMatrix.elements;
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sme[ 0 ] = dot - lightPosition4D.x * plane.normal.x;
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sme[ 4 ] = - lightPosition4D.x * plane.normal.y;
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sme[ 8 ] = - lightPosition4D.x * plane.normal.z;
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sme[ 12 ] = - lightPosition4D.x * - plane.constant;
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sme[ 1 ] = - lightPosition4D.y * plane.normal.x;
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sme[ 5 ] = dot - lightPosition4D.y * plane.normal.y;
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sme[ 9 ] = - lightPosition4D.y * plane.normal.z;
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sme[ 13 ] = - lightPosition4D.y * - plane.constant;
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sme[ 2 ] = - lightPosition4D.z * plane.normal.x;
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sme[ 6 ] = - lightPosition4D.z * plane.normal.y;
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sme[ 10 ] = dot - lightPosition4D.z * plane.normal.z;
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sme[ 14 ] = - lightPosition4D.z * - plane.constant;
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sme[ 3 ] = - lightPosition4D.w * plane.normal.x;
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sme[ 7 ] = - lightPosition4D.w * plane.normal.y;
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sme[ 11 ] = - lightPosition4D.w * plane.normal.z;
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sme[ 15 ] = dot - lightPosition4D.w * - plane.constant;
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this.matrix.multiplyMatrices( _shadowMatrix, this.meshMatrix );
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}
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}
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export { ShadowMesh };
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