Accueil / npm / three@0.186.1 / examples / jsm / geometries / LoftGeometry.js
LoftGeometry.js
import {
BufferGeometry,
Float32BufferAttribute,
ShapeUtils,
Vector2,
Vector3
} from 'three';
const _vector = /*@__PURE__*/ new Vector3();
/**
* This class can be used to generate a geometry by lofting (skinning) a surface
* through a series of cross sections. Each section is an array of points in 3D
* space and all sections must have the same number of points.
*
* `LoftGeometry` is the general case of geometries like {@link LatheGeometry}
* (which revolves a fixed profile around an axis) or {@link TubeGeometry}
* (which sweeps a circular section along a path): the sections can have any
* shape, and can change shape, size, position and orientation from one
* section to the next.
*
* Sections wind around the loft so the resulting face normals point outwards
* when each section is ordered counterclockwise as seen from the end of the
* loft, looking back towards the start. If the surface appears inside out,
* reverse the point order of each section.
*
* ```js
* const sections = [];
*
* for ( let i = 0; i <= 10; i ++ ) {
*
* const points = [];
* const radius = 2 + Math.sin( i * 0.8 );
*
* for ( let j = 0; j < 32; j ++ ) {
*
* const angle = j / 32 * Math.PI * 2;
* points.push( new THREE.Vector3( Math.sin( angle ) * radius, i, Math.cos( angle ) * radius ) );
*
* }
*
* sections.push( points );
*
* }
*
* const geometry = new LoftGeometry( sections, { capStart: true, capEnd: true } );
* const material = new THREE.MeshStandardMaterial( { color: 0x00ff00 } );
* const mesh = new THREE.Mesh( geometry, material );
* scene.add( mesh );
* ```
*
* @augments BufferGeometry
* @three_import import { LoftGeometry } from 'three/addons/geometries/LoftGeometry.js';
*/
class LoftGeometry extends BufferGeometry {
/**
* Constructs a new loft geometry.
*
* @param {Array<Array<Vector3>>} sections - The cross sections to skin. At least
* two sections are required and all sections must have the same number of points.
* @param {Object} [options={}] - The loft options.
* @param {boolean} [options.closed=true] - Whether each section is treated as a
* closed ring (e.g. a fuselage) or an open strip (e.g. a ribbon).
* @param {boolean} [options.capStart=false] - Whether the first section is closed
* with a cap or not.
* @param {boolean} [options.capEnd=false] - Whether the last section is closed
* with a cap or not.
*/
constructor( sections = [], options = {} ) {
super();
this.type = 'LoftGeometry';
const { closed = true, capStart = false, capEnd = false } = options;
/**
* Holds the constructor parameters that have been
* used to generate the geometry. Any modification
* after instantiation does not change the geometry.
*
* @type {Object}
*/
this.parameters = {
sections: sections,
closed: closed,
capStart: capStart,
capEnd: capEnd
};
const rows = sections.length;
if ( rows < 2 ) {
console.error( 'THREE.LoftGeometry: At least two sections are required.' );
return;
}
const columns = sections[ 0 ].length;
for ( let i = 1; i < rows; i ++ ) {
if ( sections[ i ].length !== columns ) {
console.error( 'THREE.LoftGeometry: All sections must have the same number of points.' );
return;
}
}
// closed sections repeat their first point so the surface can wrap
// around with continuous uvs
const pointsPerRow = closed ? columns + 1 : columns;
// buffers
const indices = [];
const vertices = [];
const uvs = [];
// uvs follow arc length so uneven sections and points map evenly
const rowU = [ 0 ];
for ( let i = 1; i < rows; i ++ ) {
let distance = 0;
for ( let j = 0; j < columns; j ++ ) {
distance += sections[ i ][ j ].distanceTo( sections[ i - 1 ][ j ] );
}
rowU.push( rowU[ i - 1 ] + distance / columns );
}
const totalU = rowU[ rows - 1 ];
// generate vertices and uvs
for ( let i = 0; i < rows; i ++ ) {
const section = sections[ i ];
// distance around the section
const colV = [ 0 ];
for ( let j = 1; j < pointsPerRow; j ++ ) {
colV.push( colV[ j - 1 ] + section[ j % columns ].distanceTo( section[ ( j - 1 ) % columns ] ) );
}
const totalV = colV[ pointsPerRow - 1 ];
for ( let j = 0; j < pointsPerRow; j ++ ) {
const point = section[ j % columns ];
vertices.push( point.x, point.y, point.z );
uvs.push(
totalU > 0 ? rowU[ i ] / totalU : i / ( rows - 1 ),
totalV > 0 ? colV[ j ] / totalV : j / ( pointsPerRow - 1 )
);
}
}
// generate indices
for ( let i = 0; i < rows - 1; i ++ ) {
for ( let j = 0; j < pointsPerRow - 1; j ++ ) {
const a = i * pointsPerRow + j;
const b = i * pointsPerRow + j + 1;
const c = ( i + 1 ) * pointsPerRow + j + 1;
const d = ( i + 1 ) * pointsPerRow + j;
// faces one and two
indices.push( a, b, d );
indices.push( b, c, d );
}
}
// generate caps
if ( capStart === true ) generateCap( 0 );
if ( capEnd === true ) generateCap( rows - 1 );
// build geometry
this.setIndex( indices );
this.setAttribute( 'position', new Float32BufferAttribute( vertices, 3 ) );
this.setAttribute( 'uv', new Float32BufferAttribute( uvs, 2 ) );
this.computeVertexNormals();
// the seam vertices of closed sections are duplicated so their computed
// normals must be averaged to achieve smooth shading across the seam
if ( closed === true ) {
const normals = this.getAttribute( 'normal' );
for ( let i = 0; i < rows; i ++ ) {
const a = i * pointsPerRow;
const b = i * pointsPerRow + ( pointsPerRow - 1 );
_vector.set(
normals.getX( a ) + normals.getX( b ),
normals.getY( a ) + normals.getY( b ),
normals.getZ( a ) + normals.getZ( b )
).normalize();
normals.setXYZ( a, _vector.x, _vector.y, _vector.z );
normals.setXYZ( b, _vector.x, _vector.y, _vector.z );
}
}
function generateCap( sectionIndex ) {
const section = sections[ sectionIndex ];
// compute the centroid of the section and the normal of its plane
// via Newell's method
const centroid = new Vector3();
const normal = new Vector3();
for ( let i = 0; i < columns; i ++ ) {
const p = section[ i ];
const q = section[ ( i + 1 ) % columns ];
centroid.add( p );
normal.x += ( p.y - q.y ) * ( p.z + q.z );
normal.y += ( p.z - q.z ) * ( p.x + q.x );
normal.z += ( p.x - q.x ) * ( p.y + q.y );
}
centroid.divideScalar( columns );
normal.normalize();
// make sure the cap faces away from the rest of the surface
const neighbor = sections[ sectionIndex === 0 ? 1 : rows - 2 ];
_vector.set( 0, 0, 0 );
for ( let i = 0; i < columns; i ++ ) _vector.add( neighbor[ i ] );
_vector.divideScalar( columns ).sub( centroid );
if ( normal.dot( _vector ) > 0 ) normal.negate();
// project the section onto the cap plane
const tangent = new Vector3( 1, 0, 0 );
if ( Math.abs( normal.x ) > 0.9 ) tangent.set( 0, 1, 0 );
const bitangent = new Vector3().crossVectors( normal, tangent ).normalize();
tangent.crossVectors( bitangent, normal );
const contour = [];
const points = section.slice();
for ( let i = 0; i < columns; i ++ ) {
_vector.subVectors( points[ i ], centroid );
contour.push( new Vector2( _vector.dot( tangent ), _vector.dot( bitangent ) ) );
}
// triangulateShape() expects contours in counterclockwise order
if ( ShapeUtils.isClockWise( contour ) === true ) {
contour.reverse();
points.reverse();
}
const faces = ShapeUtils.triangulateShape( contour, [] );
// compute the bounding box of the contour for uv generation
const min = new Vector2( Infinity, Infinity );
const max = new Vector2( - Infinity, - Infinity );
for ( let i = 0; i < columns; i ++ ) {
min.min( contour[ i ] );
max.max( contour[ i ] );
}
const width = Math.max( max.x - min.x, Number.EPSILON );
const height = Math.max( max.y - min.y, Number.EPSILON );
// generate vertices, uvs and indices; cap vertices are not shared
// with the wall so the cap is flat shaded with a hard edge
const indexOffset = vertices.length / 3;
for ( let i = 0; i < columns; i ++ ) {
const point = points[ i ];
vertices.push( point.x, point.y, point.z );
uvs.push( ( contour[ i ].x - min.x ) / width, ( contour[ i ].y - min.y ) / height );
}
for ( let i = 0; i < faces.length; i ++ ) {
const face = faces[ i ];
indices.push( indexOffset + face[ 0 ], indexOffset + face[ 1 ], indexOffset + face[ 2 ] );
}
}
}
copy( source ) {
super.copy( source );
this.parameters = Object.assign( {}, source.parameters );
return this;
}
}
export { LoftGeometry };