Chapter 23: Introducing USDZ & AR Quick Look

前言

簡單介紹了ARKit 2.0中新支援3D格式，如何利用Quick Look快速瀏覽此格式。

大綱

• What is USDZ?

• What is AR Quick Look?

• Creating USDZ files

• AR Quick Look for Web

• AR Quick Look for apps

What is USDZ?

• 這是apple所提供新的3D格式。

• USD = Universal Scene Description, Z indicates it’s a Zip archive。

• 用USDZ當3D格式的優點

  • Robust schemas for interchange of geometry, shading and skeletal deformation.

  • High performance for data retrieval, object rendering and instancing.

  • Capability to natively package user-selectable content variations.

  • Future-friendly flexible architecture designed to be easily adaptable to changing requirements

What is AR Quick Look?

• Quick Look: 用來快速瀏覽文件內容，但不用真的打開文件。例如快速查閱mail中的附件檔案內容。

• Quick Look now offers support for the new USDZ file format via its AR Quick Look feature.

• AR Quick Loook Gallery

  

Creating USDZ files

• 必須利用Xcode Command Line Tool來建立USDZ格式。

• 確保Xcode Command Line Tool在Xcode 10.0以上。

• xcrun usdz_converter(利用Xcode Command Line Tool中的usdz_converter)

  • pig.obj(input) pig.usdz(output)

  • 其他的option就是用來建立texture maps

  • -v: 打印轉換過程

xcrun usdz_converter pig.obj pig.usdz
  -color_map pig_color.png
  -metallic_map pig_metallic.png
  -roughness_map pig_roughness.png
  -normal_map pig_normal.png
  -ao_map pig_ao.png
  -v”

AR Quick Look for Web

• iOS 12, Safari has built-in support for previewing USDZ files

AR Quick Look for apps

• 利用QuickLook framework 並實作QLPreviewControllerDelegate, QLPreviewControllerDataSource完成所有功能。

import QuickLook

 class ViewController: UIViewController, UITableViewDataSource, UITableViewDelegate, QLPreviewControllerDelegate, QLPreviewControllerDataSource {}

  func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    modelIndex = indexPath.row

    // 內建原生QLPreviewController
    let previewController = QLPreviewController()
    previewController.dataSource = self
    previewController.delegate = self
    present(previewController, animated: false)
  }


  // MARK: - QLPreviewControllerDataSource

   func numberOfPreviewItems(in controller: QLPreviewController) -> Int {
        return 1
    }

   func previewController(_ controller: QLPreviewController, previewItemAt index: Int) -> QLPreviewItem {
        let url = Bundle.main.url(forResource: modelNames[modelIndex], withExtension: "usdz")!
        return url as QLPreviewItem
    }