GLTransmissionFormat.js

import { exportGltfFromTHREE } from "./utils"

// 临时解决方案，使用Three.js作为过渡，待理解glTF规范后重构
export class GLTransmissionFormat {
  // glbBuffer = null
  threeObject = null

  fromTHREE(input) {
    this.threeObject = input
    // this.glbBuffer = await exportGltfFromTHREE(input, { binary: true })
    return this
  }

  get batchLength() {
    // if (!this.glbBuffer) return null
    // const jsonChunkLength = new DataView(this.glbBuffer.slice(12, 16)).getUint32(0, true)
    // const jsonChunkBuffer = this.glbBuffer.slice(20, 20 + jsonChunkLength)
    // const glbHeader = JSON.parse(new TextDecoder("utf-8").decode(new Uint8Array(jsonChunkBuffer)))
    // const batchIdIndexArray = glbHeader?.meshes?.flatMap(({ primitives }) => primitives.map(p => p.attributes._BATCHID)).filter(i => typeof (i) === "number")

    // if (!batchIdIndexArray || batchIdIndexArray.length === 0) return 0
    // else return Math.max(...batchIdIndexArray.map(index => glbHeader.accessors[index].max[0])) + 1

    if (!this.threeObject) return null

    let maxBatchId = 0
    const stack = [this.threeObject]
    while (stack.length > 0) {
      const node = stack.pop()
      if (node.isMesh || node.isLine || node.isPoints) {
        const batchIdArray = node.geometry.attributes.batchId?.array
        if (batchIdArray) {
          for (const batchId of batchIdArray) {
            maxBatchId = Math.max(maxBatchId, batchId)
          }
        }
      }
      if (node.children && node.children.length > 0) {
        stack.push(...node.children)
      }
    }

    return maxBatchId + 1
  }

  async export(options = {}) {
    return await exportGltfFromTHREE(this.threeObject, options)
  }
}