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FAQ: Mobile Previewer

Mar 24, 2021.Knowledge

What is the recommended workflow for previewing what graphics will look like on mobile platforms?

  • There are a few ways to preview using the mobile renderer on PC.
    • Editor “Settings, Preview Rendering Level, Android ES 3.1 or iOS”. Aka “Feature Level Preview”
      • Mobile versions of the shaders, lighting and materials with Direct3D in editor viewport and in-editor PIE
      • Any settings in Android/AndroidScalability.ini or IOS/IOSScalability.ini settings are applied
      • Applies any Per-platform Property overrides
      • Shader precision limitations on device are not emulated
    • Mobile Preview ES 3.1 (PIE)
      • Same as running -featureleveles31. Standalone game instance on Windows.
      • Slightly more accurate than Feature Level Preview but not by much
    • (Experimental) Device Specific PIE
      • Same as Mobile Preview ES 3.1 (PIE) but applies local device profile ini settings.
      • Artists use and regularly toggle Preview Rendering Level inside the editor viewport and with in-editor PIE.
      • This does a good job of mobile materials, shaders, post processing, scalability settings, per-platform properties.
      • Does not emulate half-precision related issues in artist materials.
      • Does not test whatever overrides you have in device profiles.
      • But for the majority of content work on Fortnite, this is how artists create content.

Is Mobile Preview configurable for a specific device profile?

  • Currently Mobile Preview only applies scalability settings.
  • But if you setup the scalability in the way it’s intended, you can switch to Preview Rendering Level and Scalability Level and you will get what you would see on various devices in terms of LOD transitions, material qualities, foliage density scales, etc…
  • 4.25 shipped with IOS and Android scalability ini files in the same style we use in Fortnite.

Does Epic use any tools to emulate Android devices on PCs?

  • We do not use any PC based Android emulator, e.g. Bluestacks, for Development

What influences the differences between what you see on the editor vs on the mobile device?

  • Scalability/Post processing causes this difference, but there are INI file settings to help with this

Is there a recommended way to calibrate our preview of lighting in editor to match mobile devices?

  • 4.25 added eye adaptation, which helps with this
  • Issues with brightness often caused by mismatch on eye adaptation
  • Shading should be the same, but if they aren’t, it’s likely a post-processing issue
  • There are several lighting quality differences, on desktop vs mobile
    • We use half-precision GTX friendly adaptation, which was a major change around 4.23
    • Legacy lighting model setting is available