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