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UE3 Home > Mobile Home > Mobile Previewer

Mobile Previewer



Mobile Previewer allows you to visualize your game on PC using an OpenGL ES2 renderer that behaves very similarly to the rendering on the mobile device. This gives you as close to a 1:1 preview of your game without having to deploy to the device to test it. Along with graphics, some other features are emulated such as simulated touch controls.

Accessing the Mobile Previewer

The Mobile Previewer can be used to test from within UnrealEd or in the standalone game on PC, and the method you use to access it differs with each.

Mobile Previewer In Editor

The easiest way to quickly load a level in the Mobile Previewer is to click the toolbar_pip.png button on the editor's main tool bar. This will launch the Mobile Previewer so you can play the currently-loaded map.

Editor Previewer Settings

Right-clicking the toolbar_pip.png button or clicking the toolbar_pip_settings.png button will open the Mobile Previewer Settings window.


Commandline - The name of the map to load in the Mobile Previewer. This must match the name of the loaded map (with the 'UEDPC' prefix) and should not be modified.

Resolution - Sets the resolution of the Mobile Previewer window from a selection of predefined options


Options Resolution Description
Default 960x640 Sets the resolution of the Mobile Previewer to 960x640 and sets the Features to Default.
Custom Configurable Sets the resolution of the Mobile Previewer to values entered in the text fields and sets the Features to Default.
iPhone 3GS 480x320 Sets the resolution of the Mobile Previewer to 480x320 and sets the Features to iPhone 3GS.
iPad 1024x768 Sets the resolution of the Mobile Previewer to 1024x768 and sets the Features to iPad.
iPhone4 960x640 Sets the resolution of the Mobile Previewer to 960x640 and sets the Features to iPhone4.
iPhoneTouch4 960x640 Sets the resolution of the Mobile Previewer to 960x640 and sets the Features to iPhoneTouch4.

Orientation - Sets the orientation of the Mobile Previewer. This determines whether the dimensions of the resolution are interpreted as Width x Height or Height x Width.


Option Description
Landscape Resolution is interpreted as Width x Height.
Portrait Resolution is interprested as Height x Width.

Features - Determines the set of mobile emulation features for the Mobile Previewer to use.


Mobile Previewer in Standalone

Launching the game with the '-simmobile' command line argument will activate the ES2 renderer along with other mobile-related features, such as touch-based input emulation.

If you only want the ES2 renderer, but no other emulation features, you can pass the '-es2' command line argument to activate the OpenGL ES2 RHI instead of the usual DirectX-based rendering. This uses nearly the exact same code path as your mobile game uses when running on device, so the graphics will appear very similar.

Differences Between Previewer and Device

The main difference is performance, as chances are that the GPU in your your PC graphics card is much faster than your mobile device's GPU.

Mobile Previewer does not emulate the side effects of limited precision in shader uniforms and varyings. This means that sometimes an effect may appear correct in Mobile Previewer but on device will have artifacts of some sort. Usually this is caused by use of 'lowp' in the ES2 shader variables or interpolators. Precision-related shader bugs must currently always be debugged on device.

Many device-specific features, such as backgrounding, networking and audio will behave much differently in mobile previewer than on an actual device. Rememeber, Mobile Previewer is really just UE3 on PC with an OpenGL ES2 renderer and a few other emulation features (such as touch input emulation.)

Startup movies and load screens will not be previewed in Mobile Previewer.

Another important difference is that Mobile Previewer uses your PC graphics card to rasterize polygons, so some features such as anisotropic filtering, hardware mip LOD bias and antialiasing may look different on PC than on device.

Differences Between Previewer and Editor

  • The mobile previewer should be used when you want a more accurate representation of what your game will look like without running on your mobile device. The editor uses Direct3D and not the OpenGL ES2 renderer that mobile devices use. As a result, it cannot display some shading effects such as fog and mobile specular which require the use of OpenGL shaders.

  • Debug view modes such as shader complexity, wireframe, unlit, lighting only, and lighting detail are not yet supported with the mobile previewer. If you would like to use these features you should run your game via "Play in Editor" or "Play on PC". Note however that shader complexity may not be accurate as the mobile previewer does not use the same shaders as the editor.