@cesium/engine/Source/Workers/decodeDraco.js

CesiumJS is a JavaScript library for creating 3D globes and 2D maps in a web browser without a plugin.

import ComponentDatatype from "../Core/ComponentDatatype.js";
import defined from "../Core/defined.js";
import IndexDatatype from "../Core/IndexDatatype.js";
import RuntimeError from "../Core/RuntimeError.js";
import createTaskProcessorWorker from "./createTaskProcessorWorker.js";
import dracoModule from "draco3d/draco_decoder_nodejs.js";

let draco;

function decodeIndexArray(dracoGeometry, dracoDecoder) {
  const numPoints = dracoGeometry.num_points();
  const numFaces = dracoGeometry.num_faces();
  const faceIndices = new draco.DracoInt32Array();
  const numIndices = numFaces * 3;
  const indexArray = IndexDatatype.createTypedArray(numPoints, numIndices);

  let offset = 0;
  for (let i = 0; i < numFaces; ++i) {
    dracoDecoder.GetFaceFromMesh(dracoGeometry, i, faceIndices);

    indexArray[offset + 0] = faceIndices.GetValue(0);
    indexArray[offset + 1] = faceIndices.GetValue(1);
    indexArray[offset + 2] = faceIndices.GetValue(2);
    offset += 3;
  }

  draco.destroy(faceIndices);

  return {
    typedArray: indexArray,
    numberOfIndices: numIndices,
  };
}

function decodeQuantizedDracoTypedArray(
  dracoGeometry,
  dracoDecoder,
  dracoAttribute,
  quantization,
  vertexArrayLength,
) {
  let vertexArray;
  let attributeData;
  if (quantization.quantizationBits <= 8) {
    attributeData = new draco.DracoUInt8Array();
    vertexArray = new Uint8Array(vertexArrayLength);
    dracoDecoder.GetAttributeUInt8ForAllPoints(
      dracoGeometry,
      dracoAttribute,
      attributeData,
    );
  } else if (quantization.quantizationBits <= 16) {
    attributeData = new draco.DracoUInt16Array();
    vertexArray = new Uint16Array(vertexArrayLength);
    dracoDecoder.GetAttributeUInt16ForAllPoints(
      dracoGeometry,
      dracoAttribute,
      attributeData,
    );
  } else {
    attributeData = new draco.DracoFloat32Array();
    vertexArray = new Float32Array(vertexArrayLength);
    dracoDecoder.GetAttributeFloatForAllPoints(
      dracoGeometry,
      dracoAttribute,
      attributeData,
    );
  }

  for (let i = 0; i < vertexArrayLength; ++i) {
    vertexArray[i] = attributeData.GetValue(i);
  }

  draco.destroy(attributeData);
  return vertexArray;
}

function decodeDracoTypedArray(
  dracoGeometry,
  dracoDecoder,
  dracoAttribute,
  vertexArrayLength,
) {
  let vertexArray;
  let attributeData;

  // Some attribute types are casted down to 32 bit since Draco only returns 32 bit values
  switch (dracoAttribute.data_type()) {
    case 1:
    case 11: // DT_INT8 or DT_BOOL
      attributeData = new draco.DracoInt8Array();
      vertexArray = new Int8Array(vertexArrayLength);
      dracoDecoder.GetAttributeInt8ForAllPoints(
        dracoGeometry,
        dracoAttribute,
        attributeData,
      );
      break;
    case 2: // DT_UINT8
      attributeData = new draco.DracoUInt8Array();
      vertexArray = new Uint8Array(vertexArrayLength);
      dracoDecoder.GetAttributeUInt8ForAllPoints(
        dracoGeometry,
        dracoAttribute,
        attributeData,
      );
      break;
    case 3: // DT_INT16
      attributeData = new draco.DracoInt16Array();
      vertexArray = new Int16Array(vertexArrayLength);
      dracoDecoder.GetAttributeInt16ForAllPoints(
        dracoGeometry,
        dracoAttribute,
        attributeData,
      );
      break;
    case 4: // DT_UINT16
      attributeData = new draco.DracoUInt16Array();
      vertexArray = new Uint16Array(vertexArrayLength);
      dracoDecoder.GetAttributeUInt16ForAllPoints(
        dracoGeometry,
        dracoAttribute,
        attributeData,
      );
      break;
    case 5:
    case 7: // DT_INT32 or DT_INT64
      attributeData = new draco.DracoInt32Array();
      vertexArray = new Int32Array(vertexArrayLength);
      dracoDecoder.GetAttributeInt32ForAllPoints(
        dracoGeometry,
        dracoAttribute,
        attributeData,
      );
      break;
    case 6:
    case 8: // DT_UINT32 or DT_UINT64
      attributeData = new draco.DracoUInt32Array();
      vertexArray = new Uint32Array(vertexArrayLength);
      dracoDecoder.GetAttributeUInt32ForAllPoints(
        dracoGeometry,
        dracoAttribute,
        attributeData,
      );
      break;
    case 9:
    case 10: // DT_FLOAT32 or DT_FLOAT64
      attributeData = new draco.DracoFloat32Array();
      vertexArray = new Float32Array(vertexArrayLength);
      dracoDecoder.GetAttributeFloatForAllPoints(
        dracoGeometry,
        dracoAttribute,
        attributeData,
      );
      break;
  }

  for (let i = 0; i < vertexArrayLength; ++i) {
    vertexArray[i] = attributeData.GetValue(i);
  }

  draco.destroy(attributeData);
  return vertexArray;
}

function decodeAttribute(dracoGeometry, dracoDecoder, dracoAttribute) {
  const numPoints = dracoGeometry.num_points();
  const numComponents = dracoAttribute.num_components();

  let quantization;
  let transform = new draco.AttributeQuantizationTransform();
  if (transform.InitFromAttribute(dracoAttribute)) {
    const minValues = new Array(numComponents);
    for (let i = 0; i < numComponents; ++i) {
      minValues[i] = transform.min_value(i);
    }
    quantization = {
      quantizationBits: transform.quantization_bits(),
      minValues: minValues,
      range: transform.range(),
      octEncoded: false,
    };
  }
  draco.destroy(transform);

  transform = new draco.AttributeOctahedronTransform();
  if (transform.InitFromAttribute(dracoAttribute)) {
    quantization = {
      quantizationBits: transform.quantization_bits(),
      octEncoded: true,
    };
  }
  draco.destroy(transform);

  const vertexArrayLength = numPoints * numComponents;
  let vertexArray;
  if (defined(quantization)) {
    vertexArray = decodeQuantizedDracoTypedArray(
      dracoGeometry,
      dracoDecoder,
      dracoAttribute,
      quantization,
      vertexArrayLength,
    );
  } else {
    vertexArray = decodeDracoTypedArray(
      dracoGeometry,
      dracoDecoder,
      dracoAttribute,
      vertexArrayLength,
    );
  }

  const componentDatatype = ComponentDatatype.fromTypedArray(vertexArray);

  return {
    array: vertexArray,
    data: {
      componentsPerAttribute: numComponents,
      componentDatatype: componentDatatype,
      byteOffset: dracoAttribute.byte_offset(),
      byteStride:
        ComponentDatatype.getSizeInBytes(componentDatatype) * numComponents,
      normalized: dracoAttribute.normalized(),
      quantization: quantization,
    },
  };
}

function decodePointCloud(parameters) {
  const dracoDecoder = new draco.Decoder();

  if (parameters.dequantizeInShader) {
    dracoDecoder.SkipAttributeTransform(draco.POSITION);
    dracoDecoder.SkipAttributeTransform(draco.NORMAL);
  }

  const buffer = new draco.DecoderBuffer();
  buffer.Init(parameters.buffer, parameters.buffer.length);

  const geometryType = dracoDecoder.GetEncodedGeometryType(buffer);
  if (geometryType !== draco.POINT_CLOUD) {
    throw new RuntimeError("Draco geometry type must be POINT_CLOUD.");
  }

  const dracoPointCloud = new draco.PointCloud();
  const decodingStatus = dracoDecoder.DecodeBufferToPointCloud(
    buffer,
    dracoPointCloud,
  );
  if (!decodingStatus.ok() || dracoPointCloud.ptr === 0) {
    throw new RuntimeError(
      `Error decoding draco point cloud: ${decodingStatus.error_msg()}`,
    );
  }

  draco.destroy(buffer);

  const result = {};

  const properties = parameters.properties;
  for (const propertyName in properties) {
    if (properties.hasOwnProperty(propertyName)) {
      let dracoAttribute;
      if (propertyName === "POSITION" || propertyName === "NORMAL") {
        const dracoAttributeId = dracoDecoder.GetAttributeId(
          dracoPointCloud,
          draco[propertyName],
        );
        dracoAttribute = dracoDecoder.GetAttribute(
          dracoPointCloud,
          dracoAttributeId,
        );
      } else {
        const attributeId = properties[propertyName];
        dracoAttribute = dracoDecoder.GetAttributeByUniqueId(
          dracoPointCloud,
          attributeId,
        );
      }
      result[propertyName] = decodeAttribute(
        dracoPointCloud,
        dracoDecoder,
        dracoAttribute,
      );
    }
  }

  draco.destroy(dracoPointCloud);
  draco.destroy(dracoDecoder);

  return result;
}

function decodePrimitive(parameters) {
  const dracoDecoder = new draco.Decoder();

  if (parameters.dequantizeInShader) {
    for (let i = 0; i < parameters.attributesToSkipTransform.length; ++i) {
      dracoDecoder.SkipAttributeTransform(
        draco[parameters.attributesToSkipTransform[i]],
      );
    }
  }

  const bufferView = parameters.bufferView;
  const buffer = new draco.DecoderBuffer();
  buffer.Init(parameters.array, bufferView.byteLength);

  const geometryType = dracoDecoder.GetEncodedGeometryType(buffer);
  if (geometryType !== draco.TRIANGULAR_MESH) {
    throw new RuntimeError("Unsupported draco mesh geometry type.");
  }

  const dracoGeometry = new draco.Mesh();
  const decodingStatus = dracoDecoder.DecodeBufferToMesh(buffer, dracoGeometry);
  if (!decodingStatus.ok() || dracoGeometry.ptr === 0) {
    throw new RuntimeError(
      `Error decoding draco mesh geometry: ${decodingStatus.error_msg()}`,
    );
  }

  draco.destroy(buffer);

  const attributeData = {};

  const compressedAttributes = parameters.compressedAttributes;
  for (const attributeName in compressedAttributes) {
    if (compressedAttributes.hasOwnProperty(attributeName)) {
      const compressedAttribute = compressedAttributes[attributeName];
      const dracoAttribute = dracoDecoder.GetAttributeByUniqueId(
        dracoGeometry,
        compressedAttribute,
      );
      attributeData[attributeName] = decodeAttribute(
        dracoGeometry,
        dracoDecoder,
        dracoAttribute,
      );
    }
  }

  const result = {
    indexArray: decodeIndexArray(dracoGeometry, dracoDecoder),
    attributeData: attributeData,
  };

  draco.destroy(dracoGeometry);
  draco.destroy(dracoDecoder);

  return result;
}

async function decode(parameters, transferableObjects) {
  if (defined(parameters.bufferView)) {
    return decodePrimitive(parameters);
  }
  return decodePointCloud(parameters);
}

async function initWorker(parameters, transferableObjects) {
  // Require and compile WebAssembly module, or use fallback if not supported
  const wasmConfig = parameters.webAssemblyConfig;
  if (defined(wasmConfig) && defined(wasmConfig.wasmBinaryFile)) {
    draco = await dracoModule(wasmConfig);
  } else {
    draco = await dracoModule();
  }

  return true;
}

async function decodeDraco(parameters, transferableObjects) {
  // Expect the first message to be to load a web assembly module
  const wasmConfig = parameters.webAssemblyConfig;
  if (defined(wasmConfig)) {
    return initWorker(parameters, transferableObjects);
  }

  return decode(parameters, transferableObjects);
}

export default createTaskProcessorWorker(decodeDraco);