Accueil / npm / three@0.186.1 / examples / jsm / objects / ShadowMesh.js
ShadowMesh.js
import {
Matrix4,
Mesh,
MeshBasicMaterial,
EqualStencilFunc,
IncrementStencilOp
} from 'three';
const _shadowMatrix = new Matrix4();
/**
* A Shadow Mesh that follows a shadow-casting mesh in the scene,
* but is confined to a single plane. This technique can be used as
* a very performant alternative to classic shadow mapping. However,
* it has serious limitations like:
*
* - Shadows can only be casted on flat planes.
* - No soft shadows support.
*
* ```js
* const cubeShadow = new ShadowMesh( cube );
* scene.add( cubeShadow );
* ```
*
* @augments Mesh
* @three_import import { ShadowMesh } from 'three/addons/objects/ShadowMesh.js';
*/
class ShadowMesh extends Mesh {
/**
* Constructs a new shadow mesh.
*
* @param {Mesh} mesh - The shadow-casting reference mesh.
*/
constructor( mesh ) {
const shadowMaterial = new MeshBasicMaterial( {
color: 0x000000,
transparent: true,
opacity: 0.6,
depthWrite: false,
stencilWrite: true,
stencilFunc: EqualStencilFunc,
stencilRef: 0,
stencilZPass: IncrementStencilOp
} );
super( mesh.geometry, shadowMaterial );
/**
* This flag can be used for type testing.
*
* @type {boolean}
* @readonly
* @default true
*/
this.isShadowMesh = true;
/**
* Represent the world matrix of the reference mesh.
*
* @type {Matrix4}
*/
this.meshMatrix = mesh.matrixWorld;
/**
* Overwritten to disable view-frustum culling by default.
*
* @type {boolean}
* @default false
*/
this.frustumCulled = false;
/**
* Overwritten to disable automatic matrix update. The local
* matrix is computed manually in {@link ShadowMesh#update}.
*
* @type {boolean}
* @default false
*/
this.matrixAutoUpdate = false;
}
/**
* Updates the shadow mesh so it follows its shadow-casting reference mesh.
*
* @param {Plane} plane - The plane onto the shadow mesh is projected.
* @param {Vector4} lightPosition4D - The light position.
*/
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 );
}
}
export { ShadowMesh };