Generating thumbnail images of 3D model files for use with AR QuickLook

ARQLThumbnailGenerator.swift

import Foundation
import SceneKit

class ARQLThumbnailGenerator {
    private let device = MTLCreateSystemDefaultDevice()!

    /// Create a thumbnail image of the asset with the specified URL at the specified
    /// animation time. Supports loading of .scn, .usd, .usdz, .obj, and .abc files,
    /// and other formats supported by ModelIO.
    /// - Parameters:
    ///     - url: The file URL of the asset.
    ///     - size: The size (in points) at which to render the asset.
    ///     - time: The animation time to which the asset should be advanced before snapshotting.
    func thumbnail(for url: URL, size: CGSize, time: TimeInterval = 0) -> UIImage? {
        let renderer = SCNRenderer(device: device, options: [:])
        renderer.autoenablesDefaultLighting = true

        if (url.pathExtension == "scn") {
            let scene = try? SCNScene(url: url, options: nil)
            renderer.scene = scene
        } else {
            let asset = MDLAsset(url: url)
            let scene = SCNScene(mdlAsset: asset)
            renderer.scene = scene
        }

        let image = renderer.snapshot(atTime: time, with: size, antialiasingMode: .multisampling4X)
        return image
    }
}

First of all thanks for sharing, great gist 🤘

But I think you should add import SceneKit.ModelIO, because without it compiler error says: "Argument labels '(mdlAsset:)' do not match any available overloads"

Awesome gist :)

Thank you very much!

I like this, one issue is that it doesn’t seem to be loading textures correctly for me.. I see a “flat what” mesh. I’m using Apple’s test files so it’s not an issue with the models

Very useful. Call asset.loadTextures() to show the textures.

This sounds exactly like what I need, but I’ve never used swift. I have 100+ usdz files on my site (Squatties.com) that I’m trying to thumbnail from. Can anyone explain how I’d run this on my machine, and ideally batch the process by pointing it a folder on my desktop. I’d be very very grateful. I copied the code into a swift playground in the hope I’d get somewhere but I essentially don’t understand how to pass the function the parameters.

I use a bash script to curl a php script on my server to list my directory of models, then for each model I wget the file, call "swift $PLAYGROUND $file, then scp the thumbnail back to my server. A playground is actually a directory and the swift file to call from a terminal lives in there usually as "Contents.swift". Right click on the playground and "show package contents". You can access arguments in swift with "CommandLine.arguments". You could also do everything in the playground and not use bash, but I was in a hurry and curl / wget / scp seemed easy enough.

is .reality supported?!

I don't believe so. The supported formats are a subset of the constants listed here.

I got this issue while using in cellForItemAt
[SceneKit] Error: Failed to load <C3DImage 0x28016c200 src:file:///private/var/mobile/Containers/Data/Application/19E310AE-1945-417C-B09D-D215DF530BD5/Documents/fender_stratocaster.usdz [0.000000x0.000000]>

love you for this code :)