> ## Documentation Index > Fetch the complete documentation index at: https://docs.speckle.systems/llms.txt > Use this file to discover all available pages before exploring further. # AccelerationStructure > Thin wrapper around the three-mesh-bvh library's MeshBVH class with some additional specific functionality. The viewer is using [*three-mesh-bvh*](https://github.com/gkjohnson/three-mesh-bvh) as the backbone for it's BVH implementation. The AccelerationStructure class is a thin wrapper around the library's [*MeshBVH*](https://threejs.org/docs/index.html?q=box#api/en/math/Box3) class with some additional specific functionality. The speckle viewer uses a dual level BVH for optimal acceleration. The `AccelerationStructure` is the functional element of the *bottom-level* acceleration structure. Each individual object will have it's own BVH, encapsulated by an `AccelerationStructure` object. ## Constructors ### constructor ```typescript theme={null} constructor(bvh: MeshBVH) ``` Populates/constructs this acceleration structure with the backing BVH. **Parameters** * **bvh**: The backing BVH as a [*MeshBVH*](https://github.com/gkjohnson/three-mesh-bvh/blob/master/src/core/MeshBVH.js) ## Accessors ### bvh ```typescript theme={null} get bvh(): MeshBVH ``` Gets the backing BVH. **Returns**: [*MeshBVH*](https://github.com/gkjohnson/three-mesh-bvh/blob/master/src/core/MeshBVH.js) #### geometry ```typescript theme={null} get geometry(): BufferGeometry ``` Gets the three.js geometry associated to the BVH. When building a BVH, three-mesh-bvh library needs a three.js geometry as input. This is that geometry. We don't use it for rendering. **Returns**: [*BufferGeometry*](https://threejs.org/docs/index.html?q=buffer#api/en/core/BufferGeometry) ## Methods ### buildBVH ```typescript theme={null} static buildBVH( indices: number[], position: Float32Array, options: BVHOptions = DefaultBVHOptions, transform?: Matrix4 ): MeshBVH ``` Build a BVH using the provided geometry data. **Parameters** * **indices**: Geometry indices * **position**: Geometry vertex positions * **options**: [*BVHOptions*](/developers/viewer/acceleration-structure-api#bvhoptions) * *optional* **transform**: A [*Matrix4*](https://threejs.org/docs/index.html?q=matri#api/en/math/Matrix4) that transforms the geometry data before building the BVH **Returns**: [*MeshBVH*](https://github.com/gkjohnson/three-mesh-bvh/blob/master/src/core/MeshBVH.js) ### getBoundingBox ```typescript theme={null} getBoundingBox(target?: Box3): Box3 ``` Gets the aabb of the entire BVH. **Parameters** * *optional* **target**: [*Box3*](https://threejs.org/docs/index.html?q=box3#api/en/math/Box3) **Returns**: [*Box3*](https://threejs.org/docs/index.html?q=box3#api/en/math/Box3) ### getVertexAtIndex ```typescript theme={null} getVertexAtIndex(index: number): Vector3 ``` Gets position value of a vertex at the given index inside the BVH vertex position array. **Parameters** * **index**: number **Returns**: [*Vector3*](https://threejs.org/docs/index.html?q=vec#api/en/math/Vector3) ### raycast ```typescript theme={null} raycast( ray: Ray, materialOrSide: Side | Material | Material[] = FrontSide ): Intersection>[] ``` Wrapper over three-mesh-bvh raycast function. Keeps original behavior,but makes sure input and output spaces are correct. **Parameters** * **ray**: [*Ray*](https://threejs.org/docs/index.html?q=ray#api/en/math/Ray) to intersect with * **materialOrSide**: [*Side*](https://threejs.org/docs/index.html?q=Materia#api/en/constants/Materials) | [*Material*](https://threejs.org/docs/index.html?q=Materia#api/en/materials/Material) | [*Material\[\]*](https://threejs.org/docs/index.html?q=Materia#api/en/materials/Material) **Returns**: [*Intersection*](https://threejs.org/docs/index.html?q=rayc#api/en/core/Raycaster.intersectObject) ### raycastFirst ```typescript theme={null} raycastFirst( ray: Ray, materialOrSide: Side | Material | Material[] = FrontSide ): Intersection>[] ``` Identical to `raycast` but stops at first intersection found. **Parameters** * **ray**: [*Ray*](https://threejs.org/docs/index.html?q=ray#api/en/math/Ray) to intersect with * **materialOrSide**: [*Side*](https://threejs.org/docs/index.html?q=Materia#api/en/constants/Materials) | [*Material*](https://threejs.org/docs/index.html?q=Materia#api/en/materials/Material) | [*Material\[\]*](https://threejs.org/docs/index.html?q=Materia#api/en/materials/Material) **Returns**: [*Intersection*](https://threejs.org/docs/index.html?q=rayc#api/en/core/Raycaster.intersectObject) ### shapecast ```typescript theme={null} shapecast( callbacks: { intersectsBounds: ( box: Box3, isLeaf: boolean, score: number | undefined, depth: number, nodeIndex: number ) => ShapecastIntersection | boolean traverseBoundsOrder?: (box: Box3) => number } & ( | { intersectsRange: ( triangleOffset: number, triangleCount: number, contained: boolean, depth: number, nodeIndex: number, box: Box3 ) => boolean } | { intersectsTriangle: ( triangle: ExtendedTriangle, triangleIndex: number, contained: boolean, depth: number ) => boolean | void } ) ): boolean ``` Generic mechanism to intersect the BVH with various shapes/objects. The callbacks provide granular access to several stages of the BVH intersection process. **Parameters** * **callbacks**: More details [*here*](https://github.com/gkjohnson/three-mesh-bvh/tree/master?tab=readme-ov-file#shapecast) **Returns**: boolean ### transformInput ```typescript theme={null} transformInput(input: T): T ``` Transform input vector, ray or box from world space into the acceleration structure's space. All the AccelerationStructure methods that deal with querying the BVH: [getBoundingBox](/developers/viewer/acceleration-structure-api#getboundingbox), [getVertexAtIndex](/developers/viewer/acceleration-structure-api#getvertexatindex), [raycast](/developers/viewer/acceleration-structure-api#raycast), [raycastFirst](/developers/viewer/acceleration-structure-api#raycastfirst), [shapecast](/developers/viewer/acceleration-structure-api#shapecast) already call this function implicitly. **Parameters** * **input**: [*Vector3*](https://threejs.org/docs/index.html?q=vec#api/en/math/Vector3) | [*Ray*](https://threejs.org/docs/index.html?q=ray#api/en/math/Ray) | [*Box3*](https://threejs.org/docs/index.html?q=box#api/en/math/Box3) **Returns**: [*Vector3*](https://threejs.org/docs/index.html?q=vec#api/en/math/Vector3) | [*Ray*](https://threejs.org/docs/index.html?q=ray#api/en/math/Ray) | [*Box3*](https://threejs.org/docs/index.html?q=box#api/en/math/Box3)
### transformOutput ```typescript theme={null} transformOutput(output: T): T ``` Transform input vector, ray or box from the acceleration structure's space into world space. **Parameters** * **input**: [*Vector3*](https://threejs.org/docs/index.html?q=vec#api/en/math/Vector3) | [*Ray*](https://threejs.org/docs/index.html?q=ray#api/en/math/Ray) | [*Box3*](https://threejs.org/docs/index.html?q=box#api/en/math/Box3) All the AccelerationStructure methods that deal with querying the BVH: [getBoundingBox](/developers/viewer/acceleration-structure-api#getboundingbox), [getVertexAtIndex](/developers/viewer/acceleration-structure-api#getvertexatindex), [raycast](/developers/viewer/acceleration-structure-api#raycast), [raycastFirst](/developers/viewer/acceleration-structure-api#raycastfirst), [shapecast](/developers/viewer/acceleration-structure-api#shapecast) already call this function implicitly. **Returns**: [*Vector3*](https://threejs.org/docs/index.html?q=vec#api/en/math/Vector3) | [*Ray*](https://threejs.org/docs/index.html?q=ray#api/en/math/Ray) | [*Box3*](https://threejs.org/docs/index.html?q=box#api/en/math/Box3) ## Typedefs ### VectorLike ```typescript theme={null} type VectorLike = { x: number; y: number; z?: number; w?: number }; ``` Archtype for Vector2, Vector3 and Vector4. ### BVHOptions ```typescript theme={null} interface BVHOptions { strategy: SplitStrategy; maxDepth: number; maxLeafTris: number; verbose: boolean; useSharedArrayBuffer: boolean; setBoundingBox: boolean; onProgress?: () => void; [SKIP_GENERATION]: boolean; } ``` Based off the original options defined in [*three-mesh-bvh*](https://github.com/gkjohnson/three-mesh-bvh/blob/a3a7ca7b2b275606963a616c80ca1262a7e48d7f/src/core/MeshBVH.js#L29)