mirror of https://github.com/CesiumGS/obj2gltf.git
62 lines
1.7 KiB
JavaScript
62 lines
1.7 KiB
JavaScript
"use strict";
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const Cesium = require("cesium");
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const getJsonBufferPadded = require("./getJsonBufferPadded");
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const defined = Cesium.defined;
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module.exports = gltfToGlb;
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/**
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* Convert a glTF to binary glTF.
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*
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* The glTF is expected to have a single buffer and all embedded resources stored in bufferViews.
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*
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* @param {Object} gltf The glTF asset.
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* @param {Buffer} binaryBuffer The binary buffer.
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* @returns {Buffer} The glb buffer.
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*
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* @private
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*/
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function gltfToGlb(gltf, binaryBuffer) {
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const buffer = gltf.buffers[0];
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if (defined(buffer.uri)) {
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binaryBuffer = Buffer.alloc(0);
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}
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// Create padded binary scene string
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const jsonBuffer = getJsonBufferPadded(gltf);
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// Allocate buffer (Global header) + (JSON chunk header) + (JSON chunk) + (Binary chunk header) + (Binary chunk)
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const glbLength = 12 + 8 + jsonBuffer.length + 8 + binaryBuffer.length;
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const glb = Buffer.alloc(glbLength);
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// Write binary glTF header (magic, version, length)
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let byteOffset = 0;
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glb.writeUInt32LE(0x46546c67, byteOffset);
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byteOffset += 4;
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glb.writeUInt32LE(2, byteOffset);
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byteOffset += 4;
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glb.writeUInt32LE(glbLength, byteOffset);
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byteOffset += 4;
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// Write JSON Chunk header (length, type)
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glb.writeUInt32LE(jsonBuffer.length, byteOffset);
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byteOffset += 4;
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glb.writeUInt32LE(0x4e4f534a, byteOffset); // JSON
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byteOffset += 4;
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// Write JSON Chunk
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jsonBuffer.copy(glb, byteOffset);
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byteOffset += jsonBuffer.length;
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// Write Binary Chunk header (length, type)
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glb.writeUInt32LE(binaryBuffer.length, byteOffset);
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byteOffset += 4;
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glb.writeUInt32LE(0x004e4942, byteOffset); // BIN
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byteOffset += 4;
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// Write Binary Chunk
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binaryBuffer.copy(glb, byteOffset);
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return glb;
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}
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