@deepgis/quantized-mesh-decoder
Version:
Decoder for the Quantized Mesh 1.0 format
279 lines (277 loc) • 9.85 kB
JavaScript
const QUANTIZED_MESH_HEADER = new Map([
[
'centerX',
Float64Array.BYTES_PER_ELEMENT
],
[
'centerY',
Float64Array.BYTES_PER_ELEMENT
],
[
'centerZ',
Float64Array.BYTES_PER_ELEMENT
],
[
'minHeight',
Float32Array.BYTES_PER_ELEMENT
],
[
'maxHeight',
Float32Array.BYTES_PER_ELEMENT
],
[
'boundingSphereCenterX',
Float64Array.BYTES_PER_ELEMENT
],
[
'boundingSphereCenterY',
Float64Array.BYTES_PER_ELEMENT
],
[
'boundingSphereCenterZ',
Float64Array.BYTES_PER_ELEMENT
],
[
'boundingSphereRadius',
Float64Array.BYTES_PER_ELEMENT
],
[
'horizonOcclusionPointX',
Float64Array.BYTES_PER_ELEMENT
],
[
'horizonOcclusionPointY',
Float64Array.BYTES_PER_ELEMENT
],
[
'horizonOcclusionPointZ',
Float64Array.BYTES_PER_ELEMENT
]
]);
function decodeZigZag(value) {
return value >> 1 ^ -(value & 1);
}
function decodeHeader(dataView) {
let position = 0;
const header = {};
for (let [key, bytesCount] of QUANTIZED_MESH_HEADER){
const getter = bytesCount === 8 ? dataView.getFloat64 : dataView.getFloat32;
header[key] = getter.call(dataView, position, true);
position += bytesCount;
}
return {
header,
headerEndPosition: position
};
}
function decodeVertexData(dataView, headerEndPosition) {
let position = headerEndPosition;
const elementsPerVertex = 3;
const vertexCount = dataView.getUint32(position, true);
const vertexData = new Uint16Array(vertexCount * elementsPerVertex);
position += Uint32Array.BYTES_PER_ELEMENT;
const bytesPerArrayElement = Uint16Array.BYTES_PER_ELEMENT;
const elementArrayLength = vertexCount * bytesPerArrayElement;
const uArrayStartPosition = position;
const vArrayStartPosition = uArrayStartPosition + elementArrayLength;
const heightArrayStartPosition = vArrayStartPosition + elementArrayLength;
let u = 0;
let v = 0;
let height = 0;
for(let i = 0; i < vertexCount; i++){
u += decodeZigZag(dataView.getUint16(uArrayStartPosition + bytesPerArrayElement * i, true));
v += decodeZigZag(dataView.getUint16(vArrayStartPosition + bytesPerArrayElement * i, true));
height += decodeZigZag(dataView.getUint16(heightArrayStartPosition + bytesPerArrayElement * i, true));
vertexData[i] = u;
vertexData[i + vertexCount] = v;
vertexData[i + vertexCount * 2] = height;
}
position += elementArrayLength * 3;
return {
vertexData,
vertexDataEndPosition: position
};
}
function decodeIndex(buffer, position, indicesCount, bytesPerIndex, encoded = true) {
let indices;
if (bytesPerIndex === 2) {
indices = new Uint16Array(buffer, position, indicesCount);
} else {
indices = new Uint32Array(buffer, position, indicesCount);
}
if (!encoded) {
return indices;
}
let highest = 0;
for(let i = 0; i < indices.length; ++i){
let code = indices[i];
indices[i] = highest - code;
if (code === 0) {
++highest;
}
}
return indices;
}
function decodeTriangleIndices(dataView, vertexData, vertexDataEndPosition) {
let position = vertexDataEndPosition;
const elementsPerVertex = 3;
const vertexCount = vertexData.length / elementsPerVertex;
const bytesPerIndex = vertexCount > 65536 ? Uint32Array.BYTES_PER_ELEMENT : Uint16Array.BYTES_PER_ELEMENT;
if (position % bytesPerIndex !== 0) {
position += bytesPerIndex - position % bytesPerIndex;
}
const triangleCount = dataView.getUint32(position, true);
position += Uint32Array.BYTES_PER_ELEMENT;
const triangleIndicesCount = triangleCount * 3;
const triangleIndices = decodeIndex(dataView.buffer, position, triangleIndicesCount, bytesPerIndex);
position += triangleIndicesCount * bytesPerIndex;
return {
triangleIndicesEndPosition: position,
triangleIndices
};
}
function decodeEdgeIndices(dataView, vertexData, triangleIndicesEndPosition) {
let position = triangleIndicesEndPosition;
const elementsPerVertex = 3;
const vertexCount = vertexData.length / elementsPerVertex;
const bytesPerIndex = vertexCount > 65536 ? Uint32Array.BYTES_PER_ELEMENT : Uint16Array.BYTES_PER_ELEMENT;
const westVertexCount = dataView.getUint32(position, true);
position += Uint32Array.BYTES_PER_ELEMENT;
const westIndices = decodeIndex(dataView.buffer, position, westVertexCount, bytesPerIndex, false);
position += westVertexCount * bytesPerIndex;
const southVertexCount = dataView.getUint32(position, true);
position += Uint32Array.BYTES_PER_ELEMENT;
const southIndices = decodeIndex(dataView.buffer, position, southVertexCount, bytesPerIndex, false);
position += southVertexCount * bytesPerIndex;
const eastVertexCount = dataView.getUint32(position, true);
position += Uint32Array.BYTES_PER_ELEMENT;
const eastIndices = decodeIndex(dataView.buffer, position, eastVertexCount, bytesPerIndex, false);
position += eastVertexCount * bytesPerIndex;
const northVertexCount = dataView.getUint32(position, true);
position += Uint32Array.BYTES_PER_ELEMENT;
const northIndices = decodeIndex(dataView.buffer, position, northVertexCount, bytesPerIndex, false);
position += northVertexCount * bytesPerIndex;
return {
edgeIndicesEndPosition: position,
westIndices,
southIndices,
eastIndices,
northIndices
};
}
function decodeVertexNormalsExtension(extensionDataView) {
return new Uint8Array(extensionDataView.buffer, extensionDataView.byteOffset, extensionDataView.byteLength);
}
function decodeWaterMaskExtension(extensionDataView) {
return extensionDataView.buffer.slice(extensionDataView.byteOffset, extensionDataView.byteOffset + extensionDataView.byteLength);
}
function decodeMetadataExtension(extensionDataView) {
const jsonLength = extensionDataView.getUint32(0, true);
let jsonString = '';
for(let i = 0; i < jsonLength; ++i){
jsonString += String.fromCharCode(extensionDataView.getUint8(Uint32Array.BYTES_PER_ELEMENT + i));
}
return JSON.parse(jsonString);
}
function decodeExtensions(dataView, indicesEndPosition) {
const extensions = {};
if (dataView.byteLength <= indicesEndPosition) {
return {
extensions,
extensionsEndPosition: indicesEndPosition
};
}
let position = indicesEndPosition;
while(position < dataView.byteLength){
const extensionId = dataView.getUint8(position);
position += Uint8Array.BYTES_PER_ELEMENT;
const extensionLength = dataView.getUint32(position, true);
position += Uint32Array.BYTES_PER_ELEMENT;
const extensionView = new DataView(dataView.buffer, position, extensionLength);
switch(extensionId){
case 1:
{
extensions.vertexNormals = decodeVertexNormalsExtension(extensionView);
break;
}
case 2:
{
extensions.waterMask = decodeWaterMaskExtension(extensionView);
break;
}
case 4:
{
extensions.metadata = decodeMetadataExtension(extensionView);
break;
}
default:
{
console.warn(`Unknown extension with id ${extensionId}`);
}
}
position += extensionLength;
}
return {
extensions,
extensionsEndPosition: position
};
}
const DECODING_STEPS = {
header: 0,
vertices: 1,
triangleIndices: 2,
edgeIndices: 3,
extensions: 4
};
const DEFAULT_OPTIONS = {
maxDecodingStep: DECODING_STEPS.extensions
};
function decode(data, userOptions) {
const options = Object.assign({}, DEFAULT_OPTIONS, userOptions);
const view = new DataView(data);
const { header, headerEndPosition } = decodeHeader(view);
if (options.maxDecodingStep < DECODING_STEPS.vertices) {
return {
header
};
}
const { vertexData, vertexDataEndPosition } = decodeVertexData(view, headerEndPosition);
if (options.maxDecodingStep < DECODING_STEPS.triangleIndices) {
return {
header,
vertexData
};
}
const { triangleIndices, triangleIndicesEndPosition } = decodeTriangleIndices(view, vertexData, vertexDataEndPosition);
if (options.maxDecodingStep < DECODING_STEPS.edgeIndices) {
return {
header,
vertexData,
triangleIndices
};
}
const { westIndices, southIndices, eastIndices, northIndices, edgeIndicesEndPosition } = decodeEdgeIndices(view, vertexData, triangleIndicesEndPosition);
if (options.maxDecodingStep < DECODING_STEPS.extensions) {
return {
header,
vertexData,
triangleIndices,
westIndices,
northIndices,
eastIndices,
southIndices
};
}
const { extensions } = decodeExtensions(view, edgeIndicesEndPosition);
return {
header,
vertexData,
triangleIndices,
westIndices,
northIndices,
eastIndices,
southIndices,
extensions
};
}
export { DECODING_STEPS, QUANTIZED_MESH_HEADER, decode, decodeEdgeIndices, decodeExtensions, decodeHeader, decodeIndex, decodeMetadataExtension, decodeTriangleIndices, decodeVertexData, decodeVertexNormalsExtension, decodeWaterMaskExtension, decodeZigZag };