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Overview

Clip Volumes define geometric shapes that can restrict the influence of lights and cube maps onto the world. This feature is intended to replace the deprecated Light Boxes and Deferred Clip Shapes functionality.

We currently support generic geometric shapes as long as they are water tight. Note that in the following the term 'light' is used for both, lights and cube maps.


Left: clip volume, right: Red light clipped by the volume

Clip Volume Editing

Clip Volumes can be created directly in the editor by clicking the 'Edit Mode' button and then picking any of the Shape Tools.

As an alternative, Clip Volume geometry can also be loaded from CGF files via the 'Load CGF' Button.

Once a Clip Volume has been created it can be edited directly with the Designer Tools by clicking the 'Edit Mode' button.

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Clip Volumes need to be water tight and cannot overlap

Restricting Lights to Clip Volumes

Lights can be associated with Clip Volumes by either placing the light directly inside the volume or by creating an Entity Link from the light to the Clip Volume.

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Before with Light Boxes/Shapes, performing an entity link was a requirement, but with Clip Volumes this is optional and this makes setup much easier!

Once an association has been established, the 'AffectsThisAreaOnly' property on the light source will clip the light's influence to the geometry inside the Clip Volume.

One example could be with environment probes, if your global probe is set to "AffectsThisAreaOnly" then the Clip Volume will occlude the ambient lighting and you'll see something like this:

Global Probe AffectThisAreaOnly TrueGlobal Probe AffectThisAreaOnly False

Restrictions

  • The Clip Volume mesh needs to be watertight.
  • Clip Volume mesh complexity has an impact on performance.
  • Each light can be linked to a maximum of two Clip Volumes.
  • Clip Volumes must not overlap.
  • Due to performance reasons, forward rendered objects perform the 'inside' test based on their pivot only.
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