A threejs helper for faces, planar, center for faces selection, ...

FaceHelpers.js

import {Vector3} from 'three';

/**
 *
 * @param refFace {Face3D}
 * @param faces {Array}
 * @returns {Array}
 */
export function findPlanarFaces(refFace, faces) {

	return faces.filter((face)=> {

		return refFace.normal.equals(face.normal);


	})


}

export function getFacesByNormalDirection(faces, normalComponent) {


	if (normalComponent == NormalComponent.positive.X) {

		return faces.filter((face)=> {

			return face.normal.x >0

		})

	}

	if (normalComponent == NormalComponent.negative.X) {

		return faces.filter((face)=> {

			return face.normal.x <0

		})

	}

	if (normalComponent == NormalComponent.positive.Y) {

		return faces.filter((face)=> {

			return face.normal.y >0

		})

	}

	if (normalComponent == NormalComponent.negative.Y) {

		return faces.filter((face)=> {

			return face.normal.y <0

		})

	}

	if (normalComponent == NormalComponent.positive.Z) {

		return faces.filter((face)=> {

			return face.normal.z >0

		})

	}

	if (normalComponent == NormalComponent.negative.Z) {

		return faces.filter((face)=> {

			return face.normal.z <0

		})

	}

}

export function getFacesByCardinalDirection(faces,cardinalDirection) {

	if(cardinalDirection == CARDINAL_DIRECTION.NORTH) return getFacesByNormalDirection(faces,NormalComponent.negative.Z);
	if(cardinalDirection == CARDINAL_DIRECTION.SOUTH) return getFacesByNormalDirection(faces,NormalComponent.positive.Z);
	if(cardinalDirection == CARDINAL_DIRECTION.EAST) return getFacesByNormalDirection(faces,NormalComponent.positive.X);
	if(cardinalDirection == CARDINAL_DIRECTION.WEST) return getFacesByNormalDirection(faces,NormalComponent.negative.X);


}


export function getFacesCenterByCardinalDirection(object,cardinalDirection,matrix) {


		object.updateWorldMatrix();
		const center = new Vector3();
		const faces =  getFacesByCardinalDirection(object.geometry.faces,cardinalDirection);
		faces.map((face,index)=>{

			let centroid = new Vector3();
			centroid.copy(object.geometry.vertices[face.a]);
			centroid.add(object.geometry.vertices[face.b]);
			centroid.add(object.geometry.vertices[face.c]);
			centroid.divideScalar(3);
			centroid.applyMatrix4(object.matrixWorld);
			center.add(centroid);

		});

		return center.divideScalar(faces.length);

}

export const NormalComponent = {
	positive: {
		X: 0,
		Y: 1,
		Z: 2
	},negative: {
		X: 3,
		Y: 4,
		Z: 5
	}

}

export const CARDINAL_DIRECTION = {
	NORTH:0,
	WEST:1,
	SOUTH:2,
	EAST:3
}