# UE4 4.9 - cast modulated shadows causes flickering on IOS dynamic characters

**URL:** <https://forums.unrealengine.com/t/ue4-4-9-cast-modulated-shadows-causes-flickering-on-ios-dynamic-characters/331609>\
**Category:** Rendering\
**Tags:** Shadows, Mobile, UE4-9, unreal-engine, flickering, iOS, question\
**Created:** [September 9, 2015, 7:56pm UTC](https://forums.unrealengine.com/t/ue4-4-9-cast-modulated-shadows-causes-flickering-on-ios-dynamic-characters/331609 "2015-09-09T19:56:24Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![anonymous\_user\_cc69b907](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@anonymous\_user\_cc69b907](https://forums.unrealengine.com/u/anonymous_user_cc69b907)\
**Post date:** [September 14, 2015, 6:13pm UTC](https://forums.unrealengine.com/t/ue4-4-9-cast-modulated-shadows-causes-flickering-on-ios-dynamic-characters/331609/2 "2015-09-14T18:13:22Z")

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Hello Anngelica,

I am sorry you having this issue.

From what you describe you have a project set for mobile IOS device. On certain characters you see a flickering shadow that resembles Z-fighting. This only occurs when you play in mobile preview but not in editor/play.

This is because this action invalidates the precalculated lighting. If the lighting was rebuilt after the change then it would work as expected.  
In deferred rendering this action causes the lighting system to revert back to dynamic preview lighting (falling back to movable lighting). That path is not currently supported by the forward renderer.

Devices that do not support depth fetch in shader (iPhone4, etc) will not even try to render decals and modulated shadows.

So if the device that you are trying to package to does not support depth fetch it won’t even try and render.

What device are you attempting to package to?

If you have not built lighting before changing from Stationary to Movable and the other way respectively then the shadows will be invalidated and not render correctly.

Here is a link to what is supported on what devices.

> **[Development Requirements](https://docs.unrealengine.com/5.1/en-US/ios-ipados-and-tvos-development-requirements-for-unreal-engine/)**
>
> iOS development requirements including compatible hardware, software, and SDK information.

This is an updated list :

> **[A new, community-hosted Unreal Engine Wiki](https://forums.unrealengine.com/t/a-new-community-hosted-unreal-engine-wiki/141494)**
>
> After over a year in maintenance mode, the official Unreal Engine Wiki is now permanently offline. These resources now live on a new community-run Unreal Engine Community Wiki — https://unrealcommunity.wiki/! You will be able to find content from...

This is our list on performance for IOS :

> **[Performance Guidelines for Mobile Devices](https://docs.unrealengine.com/5.1/en-US/performance-guidelines-for-mobile-devices-in-unreal-engine/)**
>
> Optimizing content and features for mobile games.

After looking through our documentation and determining if there is a compatibility issue, please post again with what you have found.

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