( function () {

	function computeTangents() {

		throw new Error( 'BufferGeometryUtils: computeTangents renamed to computeMikkTSpaceTangents.' );

	}

	function computeMikkTSpaceTangents( geometry, MikkTSpace, negateSign = true ) {

		if ( ! MikkTSpace || ! MikkTSpace.isReady ) {

			throw new Error( 'BufferGeometryUtils: Initialized MikkTSpace library required.' );

		}

		if ( ! geometry.hasAttribute( 'position' ) || ! geometry.hasAttribute( 'normal' ) || ! geometry.hasAttribute( 'uv' ) ) {

			throw new Error( 'BufferGeometryUtils: Tangents require "position", "normal", and "uv" attributes.' );

		}

		function getAttributeArray( attribute ) {

			if ( attribute.normalized || attribute.isInterleavedBufferAttribute ) {

				const dstArray = new Float32Array( attribute.getCount() * attribute.itemSize );
				for ( let i = 0, j = 0; i < attribute.getCount(); i ++ ) {

					dstArray[ j ++ ] = attribute.getX( i );
					dstArray[ j ++ ] = attribute.getY( i );
					if ( attribute.itemSize > 2 ) {

						dstArray[ j ++ ] = attribute.getZ( i );

					}

				}

				return dstArray;

			}

			if ( attribute.array instanceof Float32Array ) {

				return attribute.array;

			}

			return new Float32Array( attribute.array );

		}

		// MikkTSpace algorithm requires non-indexed input.

		const _geometry = geometry.index ? geometry.toNonIndexed() : geometry;

		// Compute vertex tangents.

		const tangents = MikkTSpace.generateTangents( getAttributeArray( _geometry.attributes.position ), getAttributeArray( _geometry.attributes.normal ), getAttributeArray( _geometry.attributes.uv ) );

		// Texture coordinate convention of glTF differs from the apparent
		// default of the MikkTSpace library; .w component must be flipped.

		if ( negateSign ) {

			for ( let i = 3; i < tangents.length; i += 4 ) {

				tangents[ i ] *= - 1;

			}

		}

		//

		_geometry.setAttribute( 'tangent', new THREE.BufferAttribute( tangents, 4 ) );
		if ( geometry !== _geometry ) {

			geometry.copy( _geometry );

		}

		return geometry;

	}

	/**
 * @param  {Array<BufferGeometry>} geometries
 * @param  {Boolean} useGroups
 * @return {BufferGeometry}
 */
	function mergeBufferGeometries( geometries, useGroups = false ) {

		const isIndexed = geometries[ 0 ].index !== null;
		const attributesUsed = new Set( Object.keys( geometries[ 0 ].attributes ) );
		const morphAttributesUsed = new Set( Object.keys( geometries[ 0 ].morphAttributes ) );
		const attributes = {};
		const morphAttributes = {};
		const morphTargetsRelative = geometries[ 0 ].morphTargetsRelative;
		const mergedGeometry = new THREE.BufferGeometry();
		let offset = 0;
		for ( let i = 0; i < geometries.length; ++ i ) {

			const geometry = geometries[ i ];
			let attributesCount = 0;

			// ensure that all geometries are indexed, or none

			if ( isIndexed !== ( geometry.index !== null ) ) {

				console.error( 'THREE.BufferGeometryUtils: .mergeBufferGeometries() failed with geometry at index ' + i + '. All geometries must have compatible attributes; make sure index attribute exists among all geometries, or in none of them.' );
				return null;

			}

			// gather attributes, exit early if they're different

			for ( const name in geometry.attributes ) {

				if ( ! attributesUsed.has( name ) ) {

					console.error( 'THREE.BufferGeometryUtils: .mergeBufferGeometries() failed with geometry at index ' + i + '. All geometries must have compatible attributes; make sure "' + name + '" attribute exists among all geometries, or in none of them.' );
					return null;

				}

				if ( attributes[ name ] === undefined ) attributes[ name ] = [];
				attributes[ name ].push( geometry.attributes[ name ] );
				attributesCount ++;

			}

			// ensure geometries have the same number of attributes

			if ( attributesCount !== attributesUsed.size ) {

				console.error( 'THREE.BufferGeometryUtils: .mergeBufferGeometries() failed with geometry at index ' + i + '. Make sure all geometries have the same number of attributes.' );
				return null;

			}

			// gather morph attributes, exit early if they're different

			if ( morphTargetsRelative !== geometry.morphTargetsRelative ) {

				console.error( 'THREE.BufferGeometryUtils: .mergeBufferGeometries() failed with geometry at index ' + i + '. .morphTargetsRelative must be consistent throughout all geometries.' );
				return null;

			}

			for ( const name in geometry.morphAttributes ) {

				if ( ! morphAttributesUsed.has( name ) ) {

					console.error( 'THREE.BufferGeometryUtils: .mergeBufferGeometries() failed with geometry at index ' + i + '.  .morphAttributes must be consistent throughout all geometries.' );
					return null;

				}

				if ( morphAttributes[ name ] === undefined ) morphAttributes[ name ] = [];
				morphAttributes[ name ].push( geometry.morphAttributes[ name ] );

			}

			if ( useGroups ) {

				let count;
				if ( isIndexed ) {

					count = geometry.index.count;

				} else if ( geometry.attributes.position !== undefined ) {

					count = geometry.attributes.position.count;

				} else {

					console.error( 'THREE.BufferGeometryUtils: .mergeBufferGeometries() failed with geometry at index ' + i + '. The geometry must have either an index or a position attribute' );
					return null;

				}

				mergedGeometry.addGroup( offset, count, i );
				offset += count;

			}

		}

		// merge indices

		if ( isIndexed ) {

			let indexOffset = 0;
			const mergedIndex = [];
			for ( let i = 0; i < geometries.length; ++ i ) {

				const index = geometries[ i ].index;
				for ( let j = 0; j < index.count; ++ j ) {

					mergedIndex.push( index.getX( j ) + indexOffset );

				}

				indexOffset += geometries[ i ].attributes.position.count;

			}

			mergedGeometry.setIndex( mergedIndex );

		}

		// merge attributes

		for ( const name in attributes ) {

			const mergedAttribute = mergeBufferAttributes( attributes[ name ] );
			if ( ! mergedAttribute ) {

				console.error( 'THREE.BufferGeometryUtils: .mergeBufferGeometries() failed while trying to merge the ' + name + ' attribute.' );
				return null;

			}

			mergedGeometry.setAttribute( name, mergedAttribute );

		}

		// merge morph attributes

		for ( const name in morphAttributes ) {

			const numMorphTargets = morphAttributes[ name ][ 0 ].length;
			if ( numMorphTargets === 0 ) break;
			mergedGeometry.morphAttributes = mergedGeometry.morphAttributes || {};
			mergedGeometry.morphAttributes[ name ] = [];
			for ( let i = 0; i < numMorphTargets; ++ i ) {

				const morphAttributesToMerge = [];
				for ( let j = 0; j < morphAttributes[ name ].length; ++ j ) {

					morphAttributesToMerge.push( morphAttributes[ name ][ j ][ i ] );

				}

				const mergedMorphAttribute = mergeBufferAttributes( morphAttributesToMerge );
				if ( ! mergedMorphAttribute ) {

					console.error( 'THREE.BufferGeometryUtils: .mergeBufferGeometries() failed while trying to merge the ' + name + ' morphAttribute.' );
					return null;

				}

				mergedGeometry.morphAttributes[ name ].push( mergedMorphAttribute );

			}

		}

		return mergedGeometry;

	}

	/**
 * @param {Array<BufferAttribute>} attributes
 * @return {BufferAttribute}
 */
	function mergeBufferAttributes( attributes ) {

		let TypedArray;
		let itemSize;
		let normalized;
		let arrayLength = 0;
		for ( let i = 0; i < attributes.length; ++ i ) {

			const attribute = attributes[ i ];
			if ( attribute.isInterleavedBufferAttribute ) {

				console.error( 'THREE.BufferGeometryUtils: .mergeBufferAttributes() failed. InterleavedBufferAttributes are not supported.' );
				return null;

			}

			if ( TypedArray === undefined ) TypedArray = attribute.array.constructor;
			if ( TypedArray !== attribute.array.constructor ) {

				console.error( 'THREE.BufferGeometryUtils: .mergeBufferAttributes() failed. THREE.BufferAttribute.array must be of consistent array types across matching attributes.' );
				return null;

			}

			if ( itemSize === undefined ) itemSize = attribute.itemSize;
			if ( itemSize !== attribute.itemSize ) {

				console.error( 'THREE.BufferGeometryUtils: .mergeBufferAttributes() failed. THREE.BufferAttribute.itemSize must be consistent across matching attributes.' );
				return null;

			}

			if ( normalized === undefined ) normalized = attribute.normalized;
			if ( normalized !== attribute.normalized ) {

				console.error( 'THREE.BufferGeometryUtils: .mergeBufferAttributes() failed. THREE.BufferAttribute.normalized must be consistent across matching attributes.' );
				return null;

			}

			arrayLength += attribute.array.length;

		}

		const array = new TypedArray( arrayLength );
		let offset = 0;
		for ( let i = 0; i < attributes.length; ++ i ) {

			array.set( attributes[ i ].array, offset );
			offset += attributes[ i ].array.length;

		}

		return new THREE.BufferAttribute( array, itemSize, normalized );

	}

	/**
 * @param {BufferAttribute}
 * @return {BufferAttribute}
 */
	function deepCloneAttribute( attribute ) {

		if ( attribute.isInstancedInterleavedBufferAttribute || attribute.isInterleavedBufferAttribute ) {

			return deinterleaveAttribute( attribute );

		}

		if ( attribute.isInstancedBufferAttribute ) {

			return new THREE.InstancedBufferAttribute().copy( attribute );

		}

		return new THREE.BufferAttribute().copy( attribute );

	}

	/**
 * @param {Array<BufferAttribute>} attributes
 * @return {Array<InterleavedBufferAttribute>}
 */
	function interleaveAttributes( attributes ) {

		// Interleaves the provided attributes into an THREE.InterleavedBuffer and returns
		// a set of InterleavedBufferAttributes for each attribute
		let TypedArray;
		let arrayLength = 0;
		let stride = 0;

		// calculate the length and type of the interleavedBuffer
		for ( let i = 0, l = attributes.length; i < l; ++ i ) {

			const attribute = attributes[ i ];
			if ( TypedArray === undefined ) TypedArray = attribute.array.constructor;
			if ( TypedArray !== attribute.array.constructor ) {

				console.error( 'AttributeBuffers of different types cannot be interleaved' );
				return null;

			}

			arrayLength += attribute.array.length;
			stride += attribute.itemSize;

		}

		// Create the set of buffer attributes
		const interleavedBuffer = new THREE.InterleavedBuffer( new TypedArray( arrayLength ), stride );
		let offset = 0;
		const res = [];
		const getters = [ 'getX', 'getY', 'getZ', 'getW' ];
		const setters = [ 'setX', 'setY', 'setZ', 'setW' ];
		for ( let j = 0, l = attributes.length; j < l; j ++ ) {

			const attribute = attributes[ j ];
			const itemSize = attribute.itemSize;
			const count = attribute.count;
			const iba = new THREE.InterleavedBufferAttribute( interleavedBuffer, itemSize, offset, attribute.normalized );
			res.push( iba );
			offset += itemSize;

			// Move the data for each attribute into the new interleavedBuffer
			// at the appropriate offset
			for ( let c = 0; c < count; c ++ ) {

				for ( let k = 0; k < itemSize; k ++ ) {

					iba[ setters[ k ] ]( c, attribute[ getters[ k ] ]( c ) );

				}

			}

		}

		return res;

	}

	// returns a new, non-interleaved version of the provided attribute
	function deinterleaveAttribute( attribute ) {

		const cons = attribute.data.array.constructor;
		const count = attribute.count;
		const itemSize = attribute.itemSize;
		const normalized = attribute.normalized;
		const array = new cons( count * itemSize );
		let newAttribute;
		if ( attribute.isInstancedInterleavedBufferAttribute ) {

			newAttribute = new THREE.InstancedBufferAttribute( array, itemSize, normalized, attribute.meshPerAttribute );

		} else {

			newAttribute = new THREE.BufferAttribute( array, itemSize, normalized );

		}

		for ( let i = 0; i < count; i ++ ) {

			newAttribute.setX( i, attribute.getX( i ) );
			if ( itemSize >= 2 ) {

				newAttribute.setY( i, attribute.getY( i ) );

			}

			if ( itemSize >= 3 ) {

				newAttribute.setZ( i, attribute.getZ( i ) );

			}

			if ( itemSize >= 4 ) {

				newAttribute.setW( i, attribute.getW( i ) );

			}

		}

		return newAttribute;

	}

	// deinterleaves all attributes on the geometry
	function deinterleaveGeometry( geometry ) {

		const attributes = geometry.attributes;
		const morphTargets = geometry.morphTargets;
		const attrMap = new Map();
		for ( const key in attributes ) {

			const attr = attributes[ key ];
			if ( attr.isInterleavedBufferAttribute ) {

				if ( ! attrMap.has( attr ) ) {

					attrMap.set( attr, deinterleaveAttribute( attr ) );

				}

				attributes[ key ] = attrMap.get( attr );

			}

		}

		for ( const key in morphTargets ) {

			const attr = morphTargets[ key ];
			if ( attr.isInterleavedBufferAttribute ) {

				if ( ! attrMap.has( attr ) ) {

					attrMap.set( attr, deinterleaveAttribute( attr ) );

				}

				morphTargets[ key ] = attrMap.get( attr );

			}

		}

	}

	/**
 * @param {Array<BufferGeometry>} geometry
 * @return {number}
 */
	function estimateBytesUsed( geometry ) {

		// Return the estimated memory used by this geometry in bytes
		// Calculate using itemSize, count, and BYTES_PER_ELEMENT to account
		// for InterleavedBufferAttributes.
		let mem = 0;
		for ( const name in geometry.attributes ) {

			const attr = geometry.getAttribute( name );
			mem += attr.count * attr.itemSize * attr.array.BYTES_PER_ELEMENT;

		}

		const indices = geometry.getIndex();
		mem += indices ? indices.count * indices.itemSize * indices.array.BYTES_PER_ELEMENT : 0;
		return mem;

	}

	/**
 * @param {BufferGeometry} geometry
 * @param {number} tolerance
 * @return {BufferGeometry}
 */
	function mergeVertices( geometry, tolerance = 1e-4 ) {

		tolerance = Math.max( tolerance, Number.EPSILON );

		// Generate an index buffer if the geometry doesn't have one, or optimize it
		// if it's already available.
		const hashToIndex = {};
		const indices = geometry.getIndex();
		const positions = geometry.getAttribute( 'position' );
		const vertexCount = indices ? indices.count : positions.count;

		// next value for triangle indices
		let nextIndex = 0;

		// attributes and new attribute arrays
		const attributeNames = Object.keys( geometry.attributes );
		const tmpAttributes = {};
		const tmpMorphAttributes = {};
		const newIndices = [];
		const getters = [ 'getX', 'getY', 'getZ', 'getW' ];
		const setters = [ 'setX', 'setY', 'setZ', 'setW' ];

		// Initialize the arrays, allocating space conservatively. Extra
		// space will be trimmed in the last step.
		for ( let i = 0, l = attributeNames.length; i < l; i ++ ) {

			const name = attributeNames[ i ];
			const attr = geometry.attributes[ name ];
			tmpAttributes[ name ] = new THREE.BufferAttribute( new attr.array.constructor( attr.count * attr.itemSize ), attr.itemSize, attr.normalized );
			const morphAttr = geometry.morphAttributes[ name ];
			if ( morphAttr ) {

				tmpMorphAttributes[ name ] = new THREE.BufferAttribute( new morphAttr.array.constructor( morphAttr.count * morphAttr.itemSize ), morphAttr.itemSize, morphAttr.normalized );

			}

		}

		// convert the error tolerance to an amount of decimal places to truncate to
		const decimalShift = Math.log10( 1 / tolerance );
		const shiftMultiplier = Math.pow( 10, decimalShift );
		for ( let i = 0; i < vertexCount; i ++ ) {

			const index = indices ? indices.getX( i ) : i;

			// Generate a hash for the vertex attributes at the current index 'i'
			let hash = '';
			for ( let j = 0, l = attributeNames.length; j < l; j ++ ) {

				const name = attributeNames[ j ];
				const attribute = geometry.getAttribute( name );
				const itemSize = attribute.itemSize;
				for ( let k = 0; k < itemSize; k ++ ) {

					// double tilde truncates the decimal value
					hash += `${~ ~ ( attribute[ getters[ k ] ]( index ) * shiftMultiplier )},`;

				}

			}

			// Add another reference to the vertex if it's already
			// used by another index
			if ( hash in hashToIndex ) {

				newIndices.push( hashToIndex[ hash ] );

			} else {

				// copy data to the new index in the temporary attributes
				for ( let j = 0, l = attributeNames.length; j < l; j ++ ) {

					const name = attributeNames[ j ];
					const attribute = geometry.getAttribute( name );
					const morphAttr = geometry.morphAttributes[ name ];
					const itemSize = attribute.itemSize;
					const newarray = tmpAttributes[ name ];
					const newMorphArrays = tmpMorphAttributes[ name ];
					for ( let k = 0; k < itemSize; k ++ ) {

						const getterFunc = getters[ k ];
						const setterFunc = setters[ k ];
						newarray[ setterFunc ]( nextIndex, attribute[ getterFunc ]( index ) );
						if ( morphAttr ) {

							for ( let m = 0, ml = morphAttr.length; m < ml; m ++ ) {

								newMorphArrays[ m ][ setterFunc ]( nextIndex, morphAttr[ m ][ getterFunc ]( index ) );

							}

						}

					}

				}

				hashToIndex[ hash ] = nextIndex;
				newIndices.push( nextIndex );
				nextIndex ++;

			}

		}

		// generate result THREE.BufferGeometry
		const result = geometry.clone();
		for ( const name in geometry.attributes ) {

			const tmpAttribute = tmpAttributes[ name ];
			result.setAttribute( name, new THREE.BufferAttribute( tmpAttribute.array.slice( 0, nextIndex * tmpAttribute.itemSize ), tmpAttribute.itemSize, tmpAttribute.normalized ) );
			if ( ! ( name in tmpMorphAttributes ) ) continue;
			for ( let j = 0; j < tmpMorphAttributes[ name ].length; j ++ ) {

				const tmpMorphAttribute = tmpMorphAttributes[ name ][ j ];
				result.morphAttributes[ name ][ j ] = new THREE.BufferAttribute( tmpMorphAttribute.array.slice( 0, nextIndex * tmpMorphAttribute.itemSize ), tmpMorphAttribute.itemSize, tmpMorphAttribute.normalized );

			}

		}

		// indices

		result.setIndex( newIndices );
		return result;

	}

	/**
 * @param {BufferGeometry} geometry
 * @param {number} drawMode
 * @return {BufferGeometry}
 */
	function toTrianglesDrawMode( geometry, drawMode ) {

		if ( drawMode === THREE.TrianglesDrawMode ) {

			console.warn( 'THREE.BufferGeometryUtils.toTrianglesDrawMode(): Geometry already defined as triangles.' );
			return geometry;

		}

		if ( drawMode === THREE.TriangleFanDrawMode || drawMode === THREE.TriangleStripDrawMode ) {

			let index = geometry.getIndex();

			// generate index if not present

			if ( index === null ) {

				const indices = [];
				const position = geometry.getAttribute( 'position' );
				if ( position !== undefined ) {

					for ( let i = 0; i < position.count; i ++ ) {

						indices.push( i );

					}

					geometry.setIndex( indices );
					index = geometry.getIndex();

				} else {

					console.error( 'THREE.BufferGeometryUtils.toTrianglesDrawMode(): Undefined position attribute. Processing not possible.' );
					return geometry;

				}

			}

			//

			const numberOfTriangles = index.count - 2;
			const newIndices = [];
			if ( drawMode === THREE.TriangleFanDrawMode ) {

				// gl.TRIANGLE_FAN

				for ( let i = 1; i <= numberOfTriangles; i ++ ) {

					newIndices.push( index.getX( 0 ) );
					newIndices.push( index.getX( i ) );
					newIndices.push( index.getX( i + 1 ) );

				}

			} else {

				// gl.TRIANGLE_STRIP

				for ( let i = 0; i < numberOfTriangles; i ++ ) {

					if ( i % 2 === 0 ) {

						newIndices.push( index.getX( i ) );
						newIndices.push( index.getX( i + 1 ) );
						newIndices.push( index.getX( i + 2 ) );

					} else {

						newIndices.push( index.getX( i + 2 ) );
						newIndices.push( index.getX( i + 1 ) );
						newIndices.push( index.getX( i ) );

					}

				}

			}

			if ( newIndices.length / 3 !== numberOfTriangles ) {

				console.error( 'THREE.BufferGeometryUtils.toTrianglesDrawMode(): Unable to generate correct amount of triangles.' );

			}

			// build final geometry

			const newGeometry = geometry.clone();
			newGeometry.setIndex( newIndices );
			newGeometry.clearGroups();
			return newGeometry;

		} else {

			console.error( 'THREE.BufferGeometryUtils.toTrianglesDrawMode(): Unknown draw mode:', drawMode );
			return geometry;

		}

	}

	/**
 * Calculates the morphed attributes of a morphed/skinned THREE.BufferGeometry.
 * Helpful for Raytracing or Decals.
 * @param {Mesh | Line | Points} object An instance of Mesh, Line or Points.
 * @return {Object} An Object with original position/normal attributes and morphed ones.
 */
	function computeMorphedAttributes( object ) {

		if ( object.geometry.isBufferGeometry !== true ) {

			console.error( 'THREE.BufferGeometryUtils: Geometry is not of type THREE.BufferGeometry.' );
			return null;

		}

		const _vA = new THREE.Vector3();
		const _vB = new THREE.Vector3();
		const _vC = new THREE.Vector3();
		const _tempA = new THREE.Vector3();
		const _tempB = new THREE.Vector3();
		const _tempC = new THREE.Vector3();
		const _morphA = new THREE.Vector3();
		const _morphB = new THREE.Vector3();
		const _morphC = new THREE.Vector3();
		function _calculateMorphedAttributeData( object, attribute, morphAttribute, morphTargetsRelative, a, b, c, modifiedAttributeArray ) {

			_vA.fromBufferAttribute( attribute, a );
			_vB.fromBufferAttribute( attribute, b );
			_vC.fromBufferAttribute( attribute, c );
			const morphInfluences = object.morphTargetInfluences;
			if ( morphAttribute && morphInfluences ) {

				_morphA.set( 0, 0, 0 );
				_morphB.set( 0, 0, 0 );
				_morphC.set( 0, 0, 0 );
				for ( let i = 0, il = morphAttribute.length; i < il; i ++ ) {

					const influence = morphInfluences[ i ];
					const morph = morphAttribute[ i ];
					if ( influence === 0 ) continue;
					_tempA.fromBufferAttribute( morph, a );
					_tempB.fromBufferAttribute( morph, b );
					_tempC.fromBufferAttribute( morph, c );
					if ( morphTargetsRelative ) {

						_morphA.addScaledVector( _tempA, influence );
						_morphB.addScaledVector( _tempB, influence );
						_morphC.addScaledVector( _tempC, influence );

					} else {

						_morphA.addScaledVector( _tempA.sub( _vA ), influence );
						_morphB.addScaledVector( _tempB.sub( _vB ), influence );
						_morphC.addScaledVector( _tempC.sub( _vC ), influence );

					}

				}

				_vA.add( _morphA );
				_vB.add( _morphB );
				_vC.add( _morphC );

			}

			if ( object.isSkinnedMesh ) {

				object.boneTransform( a, _vA );
				object.boneTransform( b, _vB );
				object.boneTransform( c, _vC );

			}

			modifiedAttributeArray[ a * 3 + 0 ] = _vA.x;
			modifiedAttributeArray[ a * 3 + 1 ] = _vA.y;
			modifiedAttributeArray[ a * 3 + 2 ] = _vA.z;
			modifiedAttributeArray[ b * 3 + 0 ] = _vB.x;
			modifiedAttributeArray[ b * 3 + 1 ] = _vB.y;
			modifiedAttributeArray[ b * 3 + 2 ] = _vB.z;
			modifiedAttributeArray[ c * 3 + 0 ] = _vC.x;
			modifiedAttributeArray[ c * 3 + 1 ] = _vC.y;
			modifiedAttributeArray[ c * 3 + 2 ] = _vC.z;

		}

		const geometry = object.geometry;
		const material = object.material;
		let a, b, c;
		const index = geometry.index;
		const positionAttribute = geometry.attributes.position;
		const morphPosition = geometry.morphAttributes.position;
		const morphTargetsRelative = geometry.morphTargetsRelative;
		const normalAttribute = geometry.attributes.normal;
		const morphNormal = geometry.morphAttributes.position;
		const groups = geometry.groups;
		const drawRange = geometry.drawRange;
		let i, j, il, jl;
		let group;
		let start, end;
		const modifiedPosition = new Float32Array( positionAttribute.count * positionAttribute.itemSize );
		const modifiedNormal = new Float32Array( normalAttribute.count * normalAttribute.itemSize );
		if ( index !== null ) {

			// indexed buffer geometry

			if ( Array.isArray( material ) ) {

				for ( i = 0, il = groups.length; i < il; i ++ ) {

					group = groups[ i ];
					start = Math.max( group.start, drawRange.start );
					end = Math.min( group.start + group.count, drawRange.start + drawRange.count );
					for ( j = start, jl = end; j < jl; j += 3 ) {

						a = index.getX( j );
						b = index.getX( j + 1 );
						c = index.getX( j + 2 );
						_calculateMorphedAttributeData( object, positionAttribute, morphPosition, morphTargetsRelative, a, b, c, modifiedPosition );
						_calculateMorphedAttributeData( object, normalAttribute, morphNormal, morphTargetsRelative, a, b, c, modifiedNormal );

					}

				}

			} else {

				start = Math.max( 0, drawRange.start );
				end = Math.min( index.count, drawRange.start + drawRange.count );
				for ( i = start, il = end; i < il; i += 3 ) {

					a = index.getX( i );
					b = index.getX( i + 1 );
					c = index.getX( i + 2 );
					_calculateMorphedAttributeData( object, positionAttribute, morphPosition, morphTargetsRelative, a, b, c, modifiedPosition );
					_calculateMorphedAttributeData( object, normalAttribute, morphNormal, morphTargetsRelative, a, b, c, modifiedNormal );

				}

			}

		} else {

			// non-indexed buffer geometry

			if ( Array.isArray( material ) ) {

				for ( i = 0, il = groups.length; i < il; i ++ ) {

					group = groups[ i ];
					start = Math.max( group.start, drawRange.start );
					end = Math.min( group.start + group.count, drawRange.start + drawRange.count );
					for ( j = start, jl = end; j < jl; j += 3 ) {

						a = j;
						b = j + 1;
						c = j + 2;
						_calculateMorphedAttributeData( object, positionAttribute, morphPosition, morphTargetsRelative, a, b, c, modifiedPosition );
						_calculateMorphedAttributeData( object, normalAttribute, morphNormal, morphTargetsRelative, a, b, c, modifiedNormal );

					}

				}

			} else {

				start = Math.max( 0, drawRange.start );
				end = Math.min( positionAttribute.count, drawRange.start + drawRange.count );
				for ( i = start, il = end; i < il; i += 3 ) {

					a = i;
					b = i + 1;
					c = i + 2;
					_calculateMorphedAttributeData( object, positionAttribute, morphPosition, morphTargetsRelative, a, b, c, modifiedPosition );
					_calculateMorphedAttributeData( object, normalAttribute, morphNormal, morphTargetsRelative, a, b, c, modifiedNormal );

				}

			}

		}

		const morphedPositionAttribute = new THREE.Float32BufferAttribute( modifiedPosition, 3 );
		const morphedNormalAttribute = new THREE.Float32BufferAttribute( modifiedNormal, 3 );
		return {
			positionAttribute: positionAttribute,
			normalAttribute: normalAttribute,
			morphedPositionAttribute: morphedPositionAttribute,
			morphedNormalAttribute: morphedNormalAttribute
		};

	}

	function mergeGroups( geometry ) {

		if ( geometry.groups.length === 0 ) {

			console.warn( 'THREE.BufferGeometryUtils.mergeGroups(): No groups are defined. Nothing to merge.' );
			return geometry;

		}

		let groups = geometry.groups;

		// sort groups by material index

		groups = groups.sort( ( a, b ) => {

			if ( a.materialIndex !== b.materialIndex ) return a.materialIndex - b.materialIndex;
			return a.start - b.start;

		} );

		// create index for non-indexed geometries

		if ( geometry.getIndex() === null ) {

			const positionAttribute = geometry.getAttribute( 'position' );
			const indices = [];
			for ( let i = 0; i < positionAttribute.count; i += 3 ) {

				indices.push( i, i + 1, i + 2 );

			}

			geometry.setIndex( indices );

		}

		// sort index

		const index = geometry.getIndex();
		const newIndices = [];
		for ( let i = 0; i < groups.length; i ++ ) {

			const group = groups[ i ];
			const groupStart = group.start;
			const groupLength = groupStart + group.count;
			for ( let j = groupStart; j < groupLength; j ++ ) {

				newIndices.push( index.getX( j ) );

			}

		}

		geometry.dispose(); // Required to force buffer recreation
		geometry.setIndex( newIndices );

		// update groups indices

		let start = 0;
		for ( let i = 0; i < groups.length; i ++ ) {

			const group = groups[ i ];
			group.start = start;
			start += group.count;

		}

		// merge groups

		let currentGroup = groups[ 0 ];
		geometry.groups = [ currentGroup ];
		for ( let i = 1; i < groups.length; i ++ ) {

			const group = groups[ i ];
			if ( currentGroup.materialIndex === group.materialIndex ) {

				currentGroup.count += group.count;

			} else {

				currentGroup = group;
				geometry.groups.push( currentGroup );

			}

		}

		return geometry;

	}

	// Creates a new, non-indexed geometry with smooth normals everywhere except faces that meet at
	// an angle greater than the crease angle.
	function toCreasedNormals( geometry, creaseAngle = Math.PI / 3 /* 60 degrees */ ) {

		const creaseDot = Math.cos( creaseAngle );
		const hashMultiplier = ( 1 + 1e-10 ) * 1e2;

		// reusable vertors
		const verts = [ new THREE.Vector3(), new THREE.Vector3(), new THREE.Vector3() ];
		const tempVec1 = new THREE.Vector3();
		const tempVec2 = new THREE.Vector3();
		const tempNorm = new THREE.Vector3();
		const tempNorm2 = new THREE.Vector3();

		// hashes a vector
		function hashVertex( v ) {

			const x = ~ ~ ( v.x * hashMultiplier );
			const y = ~ ~ ( v.y * hashMultiplier );
			const z = ~ ~ ( v.z * hashMultiplier );
			return `${x},${y},${z}`;

		}

		const resultGeometry = geometry.toNonIndexed();
		const posAttr = resultGeometry.attributes.position;
		const vertexMap = {};

		// find all the normals shared by commonly located vertices
		for ( let i = 0, l = posAttr.count / 3; i < l; i ++ ) {

			const i3 = 3 * i;
			const a = verts[ 0 ].fromBufferAttribute( posAttr, i3 + 0 );
			const b = verts[ 1 ].fromBufferAttribute( posAttr, i3 + 1 );
			const c = verts[ 2 ].fromBufferAttribute( posAttr, i3 + 2 );
			tempVec1.subVectors( c, b );
			tempVec2.subVectors( a, b );

			// add the normal to the map for all vertices
			const normal = new THREE.Vector3().crossVectors( tempVec1, tempVec2 ).normalize();
			for ( let n = 0; n < 3; n ++ ) {

				const vert = verts[ n ];
				const hash = hashVertex( vert );
				if ( ! ( hash in vertexMap ) ) {

					vertexMap[ hash ] = [];

				}

				vertexMap[ hash ].push( normal );

			}

		}

		// average normals from all vertices that share a common location if they are within the
		// provided crease threshold
		const normalArray = new Float32Array( posAttr.count * 3 );
		const normAttr = new THREE.BufferAttribute( normalArray, 3, false );
		for ( let i = 0, l = posAttr.count / 3; i < l; i ++ ) {

			// get the face normal for this vertex
			const i3 = 3 * i;
			const a = verts[ 0 ].fromBufferAttribute( posAttr, i3 + 0 );
			const b = verts[ 1 ].fromBufferAttribute( posAttr, i3 + 1 );
			const c = verts[ 2 ].fromBufferAttribute( posAttr, i3 + 2 );
			tempVec1.subVectors( c, b );
			tempVec2.subVectors( a, b );
			tempNorm.crossVectors( tempVec1, tempVec2 ).normalize();

			// average all normals that meet the threshold and set the normal value
			for ( let n = 0; n < 3; n ++ ) {

				const vert = verts[ n ];
				const hash = hashVertex( vert );
				const otherNormals = vertexMap[ hash ];
				tempNorm2.set( 0, 0, 0 );
				for ( let k = 0, lk = otherNormals.length; k < lk; k ++ ) {

					const otherNorm = otherNormals[ k ];
					if ( tempNorm.dot( otherNorm ) > creaseDot ) {

						tempNorm2.add( otherNorm );

					}

				}

				tempNorm2.normalize();
				normAttr.setXYZ( i3 + n, tempNorm2.x, tempNorm2.y, tempNorm2.z );

			}

		}

		resultGeometry.setAttribute( 'normal', normAttr );
		return resultGeometry;

	}

	THREE.BufferGeometryUtils = {};
	THREE.BufferGeometryUtils.computeMikkTSpaceTangents = computeMikkTSpaceTangents;
	THREE.BufferGeometryUtils.computeMorphedAttributes = computeMorphedAttributes;
	THREE.BufferGeometryUtils.computeTangents = computeTangents;
	THREE.BufferGeometryUtils.deepCloneAttribute = deepCloneAttribute;
	THREE.BufferGeometryUtils.deinterleaveAttribute = deinterleaveAttribute;
	THREE.BufferGeometryUtils.deinterleaveGeometry = deinterleaveGeometry;
	THREE.BufferGeometryUtils.estimateBytesUsed = estimateBytesUsed;
	THREE.BufferGeometryUtils.interleaveAttributes = interleaveAttributes;
	THREE.BufferGeometryUtils.mergeBufferAttributes = mergeBufferAttributes;
	THREE.BufferGeometryUtils.mergeBufferGeometries = mergeBufferGeometries;
	THREE.BufferGeometryUtils.mergeGroups = mergeGroups;
	THREE.BufferGeometryUtils.mergeVertices = mergeVertices;
	THREE.BufferGeometryUtils.toCreasedNormals = toCreasedNormals;
	THREE.BufferGeometryUtils.toTrianglesDrawMode = toTrianglesDrawMode;

} )();