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import {
BufferGeometry,
Euler,
Float32BufferAttribute,
Matrix3,
Matrix4,
Mesh,
Vector3
} from 'three';
/**
* You can use this geometry to create a decal mesh, that serves different kinds of purposes.
* e.g. adding unique details to models, performing dynamic visual environmental changes or covering seams.
*
* Constructor parameter:
*
* mesh — Any mesh object
* position — Position of the decal projector
* orientation — Orientation of the decal projector
* size — Size of the decal projector
*
* reference: http://blog.wolfire.com/2009/06/how-to-project-decals/
*
*/
class DecalGeometry extends BufferGeometry {
constructor( mesh = new Mesh(), position = new Vector3(), orientation = new Euler(), size = new Vector3( 1, 1, 1 ) ) {
super();
// buffers
const vertices = [];
const normals = [];
const uvs = [];
// helpers
const plane = new Vector3();
const normalMatrix = new Matrix3().getNormalMatrix( mesh.matrixWorld );
// this matrix represents the transformation of the decal projector
const projectorMatrix = new Matrix4();
projectorMatrix.makeRotationFromEuler( orientation );
projectorMatrix.setPosition( position );
const projectorMatrixInverse = new Matrix4();
projectorMatrixInverse.copy( projectorMatrix ).invert();
// generate buffers
generate();
// build geometry
this.setAttribute( 'position', new Float32BufferAttribute( vertices, 3 ) );
this.setAttribute( 'uv', new Float32BufferAttribute( uvs, 2 ) );
if ( normals.length > 0 ) {
this.setAttribute( 'normal', new Float32BufferAttribute( normals, 3 ) );
}
//
function generate() {
let decalVertices = [];
const vertex = new Vector3();
const normal = new Vector3();
// handle different geometry types
const geometry = mesh.geometry;
const positionAttribute = geometry.attributes.position;
const normalAttribute = geometry.attributes.normal;
// first, create an array of 'DecalVertex' objects
// three consecutive 'DecalVertex' objects represent a single face
//
// this data structure will be later used to perform the clipping
if ( geometry.index !== null ) {
// indexed BufferGeometry
const index = geometry.index;
for ( let i = 0; i < index.count; i ++ ) {
vertex.fromBufferAttribute( positionAttribute, index.getX( i ) );
if ( normalAttribute ) {
normal.fromBufferAttribute( normalAttribute, index.getX( i ) );
pushDecalVertex( decalVertices, vertex, normal );
} else {
pushDecalVertex( decalVertices, vertex );
}
}
} else {
if ( positionAttribute === undefined ) return; // empty geometry
// non-indexed BufferGeometry
for ( let i = 0; i < positionAttribute.count; i ++ ) {
vertex.fromBufferAttribute( positionAttribute, i );
if ( normalAttribute ) {
normal.fromBufferAttribute( normalAttribute, i );
pushDecalVertex( decalVertices, vertex, normal );
} else {
pushDecalVertex( decalVertices, vertex );
}
}
}
// second, clip the geometry so that it doesn't extend out from the projector
decalVertices = clipGeometry( decalVertices, plane.set( 1, 0, 0 ) );
decalVertices = clipGeometry( decalVertices, plane.set( - 1, 0, 0 ) );
decalVertices = clipGeometry( decalVertices, plane.set( 0, 1, 0 ) );
decalVertices = clipGeometry( decalVertices, plane.set( 0, - 1, 0 ) );
decalVertices = clipGeometry( decalVertices, plane.set( 0, 0, 1 ) );
decalVertices = clipGeometry( decalVertices, plane.set( 0, 0, - 1 ) );
// third, generate final vertices, normals and uvs
for ( let i = 0; i < decalVertices.length; i ++ ) {
const decalVertex = decalVertices[ i ];
// create texture coordinates (we are still in projector space)
uvs.push(
0.5 + ( decalVertex.position.x / size.x ),
0.5 + ( decalVertex.position.y / size.y )
);
// transform the vertex back to world space
decalVertex.position.applyMatrix4( projectorMatrix );
// now create vertex and normal buffer data
vertices.push( decalVertex.position.x, decalVertex.position.y, decalVertex.position.z );
if ( decalVertex.normal !== null ) {
normals.push( decalVertex.normal.x, decalVertex.normal.y, decalVertex.normal.z );
}
}
}
function pushDecalVertex( decalVertices, vertex, normal = null ) {
// transform the vertex to world space, then to projector space
vertex.applyMatrix4( mesh.matrixWorld );
vertex.applyMatrix4( projectorMatrixInverse );
if ( normal ) {
normal.applyNormalMatrix( normalMatrix );
decalVertices.push( new DecalVertex( vertex.clone(), normal.clone() ) );
} else {
decalVertices.push( new DecalVertex( vertex.clone() ) );
}
}
function clipGeometry( inVertices, plane ) {
const outVertices = [];
const s = 0.5 * Math.abs( size.dot( plane ) );
// a single iteration clips one face,
// which consists of three consecutive 'DecalVertex' objects
for ( let i = 0; i < inVertices.length; i += 3 ) {
let total = 0;
let nV1;
let nV2;
let nV3;
let nV4;
const d1 = inVertices[ i + 0 ].position.dot( plane ) - s;
const d2 = inVertices[ i + 1 ].position.dot( plane ) - s;
const d3 = inVertices[ i + 2 ].position.dot( plane ) - s;
const v1Out = d1 > 0;
const v2Out = d2 > 0;
const v3Out = d3 > 0;
// calculate, how many vertices of the face lie outside of the clipping plane
total = ( v1Out ? 1 : 0 ) + ( v2Out ? 1 : 0 ) + ( v3Out ? 1 : 0 );
switch ( total ) {
case 0: {
// the entire face lies inside of the plane, no clipping needed
outVertices.push( inVertices[ i ] );
outVertices.push( inVertices[ i + 1 ] );
outVertices.push( inVertices[ i + 2 ] );
break;
}
case 1: {
// one vertex lies outside of the plane, perform clipping
if ( v1Out ) {
nV1 = inVertices[ i + 1 ];
nV2 = inVertices[ i + 2 ];
nV3 = clip( inVertices[ i ], nV1, plane, s );
nV4 = clip( inVertices[ i ], nV2, plane, s );
}
if ( v2Out ) {
nV1 = inVertices[ i ];
nV2 = inVertices[ i + 2 ];
nV3 = clip( inVertices[ i + 1 ], nV1, plane, s );
nV4 = clip( inVertices[ i + 1 ], nV2, plane, s );
outVertices.push( nV3 );
outVertices.push( nV2.clone() );
outVertices.push( nV1.clone() );
outVertices.push( nV2.clone() );
outVertices.push( nV3.clone() );
outVertices.push( nV4 );
break;
}
if ( v3Out ) {
nV1 = inVertices[ i ];
nV2 = inVertices[ i + 1 ];
nV3 = clip( inVertices[ i + 2 ], nV1, plane, s );
nV4 = clip( inVertices[ i + 2 ], nV2, plane, s );
}
outVertices.push( nV1.clone() );
outVertices.push( nV2.clone() );
outVertices.push( nV3 );
outVertices.push( nV4 );
outVertices.push( nV3.clone() );
outVertices.push( nV2.clone() );
break;
}
case 2: {
// two vertices lies outside of the plane, perform clipping
if ( ! v1Out ) {
nV1 = inVertices[ i ].clone();
nV2 = clip( nV1, inVertices[ i + 1 ], plane, s );
nV3 = clip( nV1, inVertices[ i + 2 ], plane, s );
outVertices.push( nV1 );
outVertices.push( nV2 );
outVertices.push( nV3 );
}
if ( ! v2Out ) {
nV1 = inVertices[ i + 1 ].clone();
nV2 = clip( nV1, inVertices[ i + 2 ], plane, s );
nV3 = clip( nV1, inVertices[ i ], plane, s );
outVertices.push( nV1 );
outVertices.push( nV2 );
outVertices.push( nV3 );
}
if ( ! v3Out ) {
nV1 = inVertices[ i + 2 ].clone();
nV2 = clip( nV1, inVertices[ i ], plane, s );
nV3 = clip( nV1, inVertices[ i + 1 ], plane, s );
outVertices.push( nV1 );
outVertices.push( nV2 );
outVertices.push( nV3 );
}
break;
}
case 3: {
// the entire face lies outside of the plane, so let's discard the corresponding vertices
break;
}
}
}
return outVertices;
}
function clip( v0, v1, p, s ) {
const d0 = v0.position.dot( p ) - s;
const d1 = v1.position.dot( p ) - s;
const s0 = d0 / ( d0 - d1 );
const position = new Vector3(
v0.position.x + s0 * ( v1.position.x - v0.position.x ),
v0.position.y + s0 * ( v1.position.y - v0.position.y ),
v0.position.z + s0 * ( v1.position.z - v0.position.z )
);
let normal = null;
if ( v0.normal !== null && v1.normal !== null ) {
normal = new Vector3(
v0.normal.x + s0 * ( v1.normal.x - v0.normal.x ),
v0.normal.y + s0 * ( v1.normal.y - v0.normal.y ),
v0.normal.z + s0 * ( v1.normal.z - v0.normal.z )
);
}
const v = new DecalVertex( position, normal );
// need to clip more values (texture coordinates)? do it this way:
// intersectpoint.value = a.value + s * ( b.value - a.value );
return v;
}
}
}
// helper
class DecalVertex {
constructor( position, normal = null ) {
this.position = position;
this.normal = normal;
}
clone() {
const position = this.position.clone();
const normal = ( this.normal !== null ) ? this.normal.clone() : null;
return new this.constructor( position, normal );
}
}
export { DecalGeometry, DecalVertex };
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