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Sphere: Simplify some methods #24721

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merged 2 commits into from
Oct 3, 2022
Merged

Sphere: Simplify some methods #24721

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e18fd2b
Simplify some methods
WestLangley Sep 30, 2022
ad41d71
Minor improvement
WestLangley Oct 2, 2022
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45 changes: 19 additions & 26 deletions src/math/Sphere.js
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Original file line number Diff line number Diff line change
Expand Up @@ -3,8 +3,7 @@ import { Vector3 } from './Vector3.js';

const _box = /*@__PURE__*/ new Box3();
const _v1 = /*@__PURE__*/ new Vector3();
const _toFarthestPoint = /*@__PURE__*/ new Vector3();
const _toPoint = /*@__PURE__*/ new Vector3();
const _v2 = /*@__PURE__*/ new Vector3();

class Sphere {

Expand Down Expand Up @@ -164,29 +163,28 @@ class Sphere {
if ( this.isEmpty() ) {

this.center.copy( point );

this.radius = 0;

return this;

}

// from https://github.com/juj/MathGeoLib/blob/2940b99b99cfe575dd45103ef20f4019dee15b54/src/Geometry/Sphere.cpp#L649-L671

_toPoint.subVectors( point, this.center );
_v1.subVectors( point, this.center );

const lengthSq = _toPoint.lengthSq();
const lengthSq = _v1.lengthSq();

if ( lengthSq > ( this.radius * this.radius ) ) {

// calculate the minimal sphere

const length = Math.sqrt( lengthSq );
const missingRadiusHalf = ( length - this.radius ) * 0.5;

// Nudge this sphere towards the target point. Add half the missing distance to radius,
// and the other half to position. This gives a tighter enclosure, instead of if
// the whole missing distance were just added to radius.
const delta = ( length - this.radius ) * 0.5;

this.center.add( _toPoint.multiplyScalar( missingRadiusHalf / length ) );
this.radius += missingRadiusHalf;
this.center.addScaledVector( _v1, delta / length );

this.radius += delta;

}

Expand All @@ -196,39 +194,34 @@ class Sphere {

union( sphere ) {

// handle empty sphere cases
if ( sphere.isEmpty() ) {

return this;

} else if ( this.isEmpty() ) {
}

if ( this.isEmpty() ) {

this.copy( sphere );

return this;

}

// from https://github.com/juj/MathGeoLib/blob/2940b99b99cfe575dd45103ef20f4019dee15b54/src/Geometry/Sphere.cpp#L759-L769
if ( this.center.equals( sphere.center ) === true ) {

// To enclose another sphere into this sphere, we only need to enclose two points:
// 1) Enclose the farthest point on the other sphere into this sphere.
// 2) Enclose the opposite point of the farthest point into this sphere.
this.radius = Math.max( this.radius, sphere.radius );

if ( this.center.equals( sphere.center ) === true ) {
} else {

_toFarthestPoint.set( 0, 0, 1 ).multiplyScalar( sphere.radius );
_v2.subVectors( sphere.center, this.center ).setLength( sphere.radius );

this.expandByPoint( _v1.copy( sphere.center ).add( _v2 ) );

} else {

_toFarthestPoint.subVectors( sphere.center, this.center ).normalize().multiplyScalar( sphere.radius );
this.expandByPoint( _v1.copy( sphere.center ).sub( _v2 ) );

}

this.expandByPoint( _v1.copy( sphere.center ).add( _toFarthestPoint ) );
this.expandByPoint( _v1.copy( sphere.center ).sub( _toFarthestPoint ) );

return this;

}
Expand Down