CameraGeometry.js

import * as THREE from 'three';

const localVector = new THREE.Vector3();
const localVector2 = new THREE.Vector3();
const localQuaternion = new THREE.Quaternion();
const localMatrix = new THREE.Matrix4();

class CameraGeometry extends THREE.BufferGeometry {
  constructor() {
    super();

    const boxGeometry = new THREE.BoxBufferGeometry(1, 1, 1);
    const positions = new Float32Array(boxGeometry.attributes.position.array.length * 8);
    const indices = new Uint16Array(boxGeometry.index.array.length * 8);

    const _pushBoxGeometry = m => {
      const g = boxGeometry.clone();
      g.applyMatrix4(m);
      positions.set(g.attributes.position.array, positionIndex);
      for (let i = 0; i < g.index.array.length; i++) {
        indices[indexIndex + i] = g.index.array[i] + positionIndex/3;
      }
      positionIndex += g.attributes.position.array.length;
      indexIndex += g.index.array.length;
    };

    const topLeft = new THREE.Vector3(-1, 0.5, -2);
    const topRight = new THREE.Vector3(1, 0.5, -2);
    const bottomLeft = new THREE.Vector3(-1, -0.5, -2);
    const bottomRight = new THREE.Vector3(1, -0.5, -2);
    const back = new THREE.Vector3(0, 0, 0);

    const _setMatrixBetweenPoints = (m, p1, p2) => {
      const quaternion = localQuaternion.setFromRotationMatrix(
        localMatrix.lookAt(
          p1,
          p2,
          localVector.set(0, 1, 0)
        )
      );
      const position = localVector.copy(p1)
        .add(p2)
        .divideScalar(2)
        // .add(new THREE.Vector3(0, 2, 0));
      const sc = 0.01;
      const scale = localVector2.set(sc, sc, p1.distanceTo(p2));
      m.compose(position, quaternion, scale);
      return m;
    };

    let positionIndex = 0;
    let indexIndex = 0;
    [
      [topLeft, back],
      [topRight, back],
      [bottomLeft, back],
      [bottomRight, back],
      [topLeft, topRight],
      [topRight, bottomRight],
      [bottomRight, bottomLeft],
      [bottomLeft, topLeft],
    ].forEach(e => {
      const [p1, p2] = e;
      _pushBoxGeometry(
        _setMatrixBetweenPoints(localMatrix, p1, p2)
      );
    });

    this.setAttribute('position', new THREE.BufferAttribute(positions, 3));
    this.setIndex(new THREE.BufferAttribute(indices, 1));
  }
}

export {
  CameraGeometry,
};