Calculate accurate reflection and refraction

To create more detailed reflection and refraction in a scene, use a Proxy Volume. A Proxy Volume is a 3D shape onto which HDRP projects a 2D color buffer or cubemap texture that contains a rendered scene.

In the Unity Editor, this component is called a Reflection Proxy Volume, but HDRP uses the component to calculate more accurate effects in both reflection and refraction.

How reflection and refraction use a Proxy Volume

HDRP projects the color buffer or the cubemap texture from a Reflection Probe or a Planar Probe onto a Proxy Volume. HDRP then uses the Proxy Volume to calculate the depth of the point a reflected or refracted vector hits.

HDRP determines this based on a reflection and refraction hierarchy.

Assign a custom Proxy Volume to a Reflection Probe

By default, a Reflection Probe uses the shape and size of its Influence Volume as its Proxy Volume.

To assign a custom Proxy Volume to a Reflection Probe, do the following:

  1. In Projection Settings, disable Use Influence Volume As Proxy Volume.
  2. Select Add Component and select Reflection Proxy Volume.
  3. In the Reflection Proxy Volume, set the shape and size of the Proxy Volume.
  4. In the probe's Projection Settings, use Proxy Volume to select the Proxy Volume you created.

The Shape of the Proxy Volume must match the Shape of the Reflection Probe.

  • Use Box if the Shape of the Reflection Probe is Box.
  • Use Sphere if the Shape of the Reflection Probe is Sphere.
  • Use Infinite with either Reflection Probe shape.

If you disable Use Influence Volume As Proxy Volume in a probe's Projection Settings but leave Proxy Volume empty, the Proxy Volume has the Infinite shape by default.

You can reuse the same Proxy Volume with other Reflection Probes, as long as the shapes match. This is useful if you use multiple Reflection Probes in a single room, because you can reuse one room-shaped Proxy Volume for all the probes.

Resize a Proxy Volume

Use the Scene view Gizmo to visually modify the size of the Box and Sphere shapes. Click and drag the handles to move the boundaries of the Proxy Volume.


Properties

Property Description
Shape Define the shape of the Proxy Volume. The possible values are:
• Box. Sets the shape as a box. Use Box Size to change the size of the box.
• Sphere. Sets the shape as a sphere. Use Radius to change the size of the sphere.
• Infinite. Sets the shape as an infinite volume. You can't adjust the size of this volume. If your Material uses the planar refraction model and the nearest Proxy Volume uses the Infinite shape, refraction might not be noticeable.
The Shape of a Proxy Volume must match the Shape of the Reflection Probe or Planar Reflection Probe that uses it, unless you use Infinite.

Additional resources