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19: Planar Reflection in Trackless

Overview

This section describes how to create planar reflection in the Trackless scenario. The Planar reflection provided by Unreal does not work with “SceneCapture” which is a component used by PRIME VSAR cameras, so the “VR Reflection Plane” object has been developed to work around that limitation.

Setup

1. In the project’s settings, enable “Support global clip plane for Planar Reflections”.

Note: This will restart the editor and recompile all the project’s shaders. According to Epic, it will also increase the BasePass triangles cost by ~15% regardless of whether planar reflections are active.

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2. Create a VR Reflection Plane object, its purpose is to render the planar reflection from Cesium Camera point of view. Search for “VR Reflection Plane” and drag and drop the object in the level.

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3. Adjust the height (Z axis) of the VR Reflection Plane in order to match the floor’s height and place it slightly above it in order to avoid collision (aka “Z-fighting”).

The following step should be done for each Cesium Camera where the effect is visible.

4. Select the Cesium Camera (create one if it is not already done) and bind the VR Reflection Plane object via the Details Panel at the section Video Output Key.

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Note: The reflection is not displayed according to the Editor viewport’s camera. In order to visualize the final result, check the Cesium camera output in the VSAR Config panel or the video output.

Parameters

The VR Reflection Plane object has the following parameters to alter the rendering.

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  • Mesh Component: The default Static Mesh is a plane. This property is accessible in case of custom shape (e.g. reflection on a rounded surface).
  • Reflection Texture Resolution: The resolution of the texture used for the reflection pass.
    • Default: 1920x1080
  • Material: For advanced usage with custom Materials (e.g. blur, alpha mask...)
  • Enable Shadow: Enable/Disable shadow, default value is Disabled. (It should not be used in Trackless mode)
  • Enable Reflection: Enable/Disable reflection, default value is Enabled.
  • Shadow Opacity: Affects the shadow opacity, 1 is fully opaque and 0 is fully transparent. (It should not be used in Trackless mode)
    • Default: 1
  • Reflection Opacity: Affects the reflection opacity, 1 is fully opaque and 0 is fully transparent.
    • Default: 0.5
  • Hidden Actors: List of Actors excluded from the reflection rendering pass, intended for performance optimization.
    • Include Attached Actors: Also hide the Actors attached to the hidden Actors, default value is Enabled.

⚠️ VR Reflection Plane does not work when using Ray tracing: in Cesium Camera → Output Component → Video Output - Rendering → Post Process settings → Rendering features → translucency → type should be set to “Raster” instead of “Ray Tracing”

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