three-stdlib/math/MeshSurfaceSampler.js

stand-alone library of threejs examples

import { Triangle, Vector3 } from "three";
const _face = /* @__PURE__ */ new Triangle();
const _color = /* @__PURE__ */ new Vector3();
class MeshSurfaceSampler {
  constructor(mesh) {
    let geometry = mesh.geometry;
    if (geometry.index) {
      console.warn("THREE.MeshSurfaceSampler: Converting geometry to non-indexed BufferGeometry.");
      geometry = geometry.toNonIndexed();
    }
    this.geometry = geometry;
    this.randomFunction = Math.random;
    this.positionAttribute = this.geometry.getAttribute("position");
    this.colorAttribute = this.geometry.getAttribute("color");
    this.weightAttribute = null;
    this.distribution = null;
  }
  setWeightAttribute(name) {
    this.weightAttribute = name ? this.geometry.getAttribute(name) : null;
    return this;
  }
  build() {
    const positionAttribute = this.positionAttribute;
    const weightAttribute = this.weightAttribute;
    const faceWeights = new Float32Array(positionAttribute.count / 3);
    for (let i = 0; i < positionAttribute.count; i += 3) {
      let faceWeight = 1;
      if (weightAttribute) {
        faceWeight = weightAttribute.getX(i) + weightAttribute.getX(i + 1) + weightAttribute.getX(i + 2);
      }
      _face.a.fromBufferAttribute(positionAttribute, i);
      _face.b.fromBufferAttribute(positionAttribute, i + 1);
      _face.c.fromBufferAttribute(positionAttribute, i + 2);
      faceWeight *= _face.getArea();
      faceWeights[i / 3] = faceWeight;
    }
    this.distribution = new Float32Array(positionAttribute.count / 3);
    let cumulativeTotal = 0;
    for (let i = 0; i < faceWeights.length; i++) {
      cumulativeTotal += faceWeights[i];
      this.distribution[i] = cumulativeTotal;
    }
    return this;
  }
  setRandomGenerator(randomFunction) {
    this.randomFunction = randomFunction;
    return this;
  }
  sample(targetPosition, targetNormal, targetColor) {
    const faceIndex = this.sampleFaceIndex();
    return this.sampleFace(faceIndex, targetPosition, targetNormal, targetColor);
  }
  sampleFaceIndex() {
    const cumulativeTotal = this.distribution[this.distribution.length - 1];
    return this.binarySearch(this.randomFunction() * cumulativeTotal);
  }
  binarySearch(x) {
    const dist = this.distribution;
    let start = 0;
    let end = dist.length - 1;
    let index = -1;
    while (start <= end) {
      const mid = Math.ceil((start + end) / 2);
      if (mid === 0 || dist[mid - 1] <= x && dist[mid] > x) {
        index = mid;
        break;
      } else if (x < dist[mid]) {
        end = mid - 1;
      } else {
        start = mid + 1;
      }
    }
    return index;
  }
  sampleFace(faceIndex, targetPosition, targetNormal, targetColor) {
    let u = this.randomFunction();
    let v = this.randomFunction();
    if (u + v > 1) {
      u = 1 - u;
      v = 1 - v;
    }
    _face.a.fromBufferAttribute(this.positionAttribute, faceIndex * 3);
    _face.b.fromBufferAttribute(this.positionAttribute, faceIndex * 3 + 1);
    _face.c.fromBufferAttribute(this.positionAttribute, faceIndex * 3 + 2);
    targetPosition.set(0, 0, 0).addScaledVector(_face.a, u).addScaledVector(_face.b, v).addScaledVector(_face.c, 1 - (u + v));
    if (targetNormal !== void 0) {
      _face.getNormal(targetNormal);
    }
    if (targetColor !== void 0 && this.colorAttribute !== void 0) {
      _face.a.fromBufferAttribute(this.colorAttribute, faceIndex * 3);
      _face.b.fromBufferAttribute(this.colorAttribute, faceIndex * 3 + 1);
      _face.c.fromBufferAttribute(this.colorAttribute, faceIndex * 3 + 2);
      _color.set(0, 0, 0).addScaledVector(_face.a, u).addScaledVector(_face.b, v).addScaledVector(_face.c, 1 - (u + v));
      targetColor.r = _color.x;
      targetColor.g = _color.y;
      targetColor.b = _color.z;
    }
    return this;
  }
}
export {
  MeshSurfaceSampler
};
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