# [name]

A class containing utility functions for [page:BufferGeometry BufferGeometry] instances.

## Import

[name] is an add-on, and must be imported explicitly. See [link:#manual/introduction/Installation Installation / Addons].

`import * as BufferGeometryUtils from 'three/addons/utils/BufferGeometryUtils.js';`

## Methods

### [method:Object computeMikkTSpaceTangents]( [param:BufferGeometry geometry], [param:Object MikkTSpace], [param:Boolean negateSign] = true )

- geometry -- Instance of [page:BufferGeometry].
- MikkTSpace -- Instance of examples/jsm/libs/mikktspace.module.js, or mikktspace npm package. Await MikkTSpace.ready before use.
- negateSign -- Whether to negate the sign component (.w) of each tangent. Required for normal map conventions in some formats, including glTF.

Computes vertex tangents using the [link:http://www.mikktspace.com/ MikkTSpace] algorithm. MikkTSpace generates the same tangents consistently, and is used in most modelling tools and normal map bakers. Use MikkTSpace for materials with normal maps, because inconsistent tangents may lead to subtle visual issues in the normal map, particularly around mirrored UV seams.

In comparison to this method, [page:BufferGeometry.computeTangents] (a custom algorithm) generates tangents that probably will not match the tangents in other software. The custom algorithm is sufficient for general use with a [page:ShaderMaterial], and may be faster than MikkTSpace.

Returns the original [page:BufferGeometry]. Indexed geometries will be de-indexed. Requires position, normal, and uv attributes.

### [method:Object computeMorphedAttributes]( [param:Mesh | Line | Points object] )

object -- Instance of [page:Mesh Mesh] | [page:Line Line] | [page:Points Points].
Returns the current attributes (Position and Normal) of a morphed/skinned [page:Object3D Object3D] whose geometry is a [page:BufferGeometry BufferGeometry], together with the original ones: An Object with 4 properties: `positionAttribute`, `normalAttribute`, `morphedPositionAttribute` and `morphedNormalAttribute`. Helpful for Raytracing or Decals (i.e. a [page:DecalGeometry DecalGeometry] applied to a morphed Object with a [page:BufferGeometry BufferGeometry] will use the original BufferGeometry, not the morphed/skinned one, generating an incorrect result. Using this function to create a shadow Object3D the DecalGeometry can be correctly generated).

### [method:Number estimateBytesUsed]( [param:BufferGeometry geometry] )

geometry -- Instance of [page:BufferGeometry BufferGeometry] to estimate the memory use of.
Returns the amount of bytes used by all attributes to represent the geometry.

### [method:InterleavedBufferAttribute interleaveAttributes]( [param:Array attributes] )

attributes -- Array of [page:BufferAttribute BufferAttribute] instances.
Interleaves a set of attributes and returns a new array of corresponding attributes that share a single InterleavedBuffer instance. All attributes must have compatible types. If merge does not succeed, the method returns null.

### [method:BufferAttribute mergeAttributes]( [param:Array attributes] )

attributes -- Array of [page:BufferAttribute BufferAttribute] instances.
Merges a set of attributes into a single instance. All attributes must have compatible properties and types, and [page:InterleavedBufferAttribute InterleavedBufferAttributes] are not supported. If merge does not succeed, the method returns null.

### [method:BufferGeometry mergeGeometries]( [param:Array geometries], [param:Boolean useGroups] )

geometries -- Array of [page:BufferGeometry BufferGeometry] instances.
useGroups -- Whether groups should be generated for the merged geometry or not.
Merges a set of geometries into a single instance. All geometries must have compatible attributes. If merge does not succeed, the method returns null.

### [method:BufferGeometry mergeGroups]( [param:BufferGeometry geometry] )

geometry -- Instance of [page:BufferGeometry BufferGeometry] to merge the groups of.
Merges the [page:BufferGeometry.groups groups] for the given geometry.

### [method:BufferGeometry mergeVertices]( [param:BufferGeometry geometry], [param:Number tolerance] )

geometry -- Instance of [page:BufferGeometry BufferGeometry] to merge the vertices of.
tolerance -- The maximum allowable difference between vertex attributes to merge. Defaults to 1e-4.
Returns a new [page:BufferGeometry BufferGeometry] with vertices for which all similar vertex attributes (within tolerance) are merged.

### [method:BufferGeometry toCreasedNormals]( [param:BufferGeometry geometry], [param:Number creaseAngle] )

- geometry -- The input geometry.
- creaseAngle -- The crease angle in radians.

Modifies the supplied geometry if it is non-indexed, otherwise creates a new, non-indexed geometry.

Returns the geometry with smooth normals everywhere except faces that meet at an angle greater than the crease angle.

### [method:BufferGeometry toTrianglesDrawMode]( [param:BufferGeometry geometry], [param:TrianglesDrawMode drawMode] )

geometry -- Instance of [page:BufferGeometry BufferGeometry].
drawMode -- The draw mode of the given geometry. Valid inputs are `THREE.TriangleStripDrawMode` and `THREE.TriangleFanDrawMode`.
Returns a new indexed geometry based on `THREE.TrianglesDrawMode` draw mode. This mode corresponds to the `gl.TRIANGLES` WebGL primitive.

## Source

[link:https://github.com/mrdoob/three.js/blob/master/examples/jsm/utils/BufferGeometryUtils.js examples/jsm/utils/BufferGeometryUtils.js]