itowns/lib/Utils/ThreeUtils.js

A JS/WebGL framework for 3D geospatial data visualization

/**
 * Find threejs textures from a material
 * @param {Material} material the threejs material holding textures
 * @returns {Array} an array of textures in the material
 */
function findTextures(material) {
  const textures = [];
  if (material.alphaMap) {
    textures.push(material.map);
  }
  if (material.aoMap) {
    textures.push(material.map);
  }
  if (material.bumpMap) {
    textures.push(material.bumpMap);
  }
  if (material.displacementMap) {
    textures.push(material.bumpMap);
  }
  if (material.emissiveMap) {
    textures.push(material.emissiveMap);
  }
  if (material.envMap) {
    textures.push(material.envMap);
  }
  if (material.lightMap) {
    textures.push(material.envMap);
  }
  if (material.map) {
    textures.push(material.map);
  }
  if (material.metalnessMap) {
    textures.push(material.map);
  }
  if (material.normalMap) {
    textures.push(material.map);
  }
  if (material.roughnessMap) {
    textures.push(material.map);
  }
  if (material.specularMap) {
    textures.push(material.specularMap);
  }
  return textures;
}

/**
 * Removes a material and its textures, memory will be freed.
 * IMPORTANT NOTE: the material and the texture must not be referenced by other threejs objects, otherwise the memory
 * won't be freed.
 * @param {Material} material the material to remove
 */
export default function disposeThreeMaterial(material) {
  const textures = findTextures(material);
  // Remove material
  if (Array.isArray(material)) {
    for (const m of material) {
      m.dispose();
    }
  } else {
    material.dispose();
  }
  // Remove textures
  for (let i = 0; i < textures.length; i++) {
    textures[i].dispose();
  }
}

/**
 * Merge groups of an object3D when it can to reduce number of them + remove unused materials
 * Reduce draw call https://threejs.org/docs/index.html?q=geometry#api/en/core/BufferGeometry.groups
 *
 * @param {THREE.Object3D} object3D - object to get optimize
 */
export function optimizeGeometryGroups(object3D) {
  if (!object3D.geometry) {
    return;
  }
  object3D.geometry.groups.sort((a, b) => (a.start - b.start) * -1); // [5,10,7] => [10,7,5]
  const lastIndex = object3D.geometry.groups.length - 1;
  let currentMaterialIndex = object3D.geometry.groups[lastIndex].materialIndex; // initialized with the lastest group
  const usedIndexMaterials = [currentMaterialIndex]; // compute materials actually used by group
  // for loop descendant to be able to splice in loop without modifying group index
  for (let index = lastIndex - 1; index >= 0; index--) {
    // begin at lastIndex - 1 because intialized with lastIndex
    const group = object3D.geometry.groups[index];
    if (group.materialIndex !== currentMaterialIndex) {
      // this is another group (!= materialIndex) take its material as ref to continue
      currentMaterialIndex = group.materialIndex;
      usedIndexMaterials.push(currentMaterialIndex);
      continue;
    } else {
      // indeed same group merge with previous group
      const previousGroup = object3D.geometry.groups[index + 1];
      previousGroup.count += group.count; // previous group wrap the current one
      object3D.geometry.groups.splice(index, 1); // remove group
    }
  }

  // clean unused material
  for (let index = object3D.material.length - 1; index >= 0; index--) {
    if (!usedIndexMaterials.includes(index)) {
      // update all materialIndex in groups
      object3D.geometry.groups.forEach(group => {
        if (group.materialIndex > index) {
          // only materialIndex > at index are modified
          group.materialIndex -= 1;
        }
      });

      // remove
      object3D.material.splice(index, 1);
    }
  }
}