The following light filters are available in HtoA:

Arnold "light filters" are arbitrary shaders that can modify a light's output based on distance, position, or other factors. This makes it easy to extend the built-in light sources with additional effects. There are 4 light filters:


Barndoors are opaque moving panels attached to the sides of the light's opening used for additional control over the shape of the light beam. 

The gobo filter is used to break up the light beam into an irregular, more natural pattern such as tree leaves, etc.

The light_blocker filter will block out an arbitrary geometrically defined area of a connected light.

The light_decay filter specifies the attenuation ranges of where the light starts and ends.

Attaching Light Filters To Lights

Light filters are created within Arnold Shader Networks and must be connected to a light output node. The vopnet is then connected to Arnold Lights under the Light Filter tab.

By default, when you click on the filters tab of a light, a vopnet will be created already within the light. Clicking the 'Jump To' arrow will take you inside obj > arnold_light1 > shopnet > arnold_vopnet. This is created here for convenience. However, an Arnold Shader Network vopnet could be created in the SHOP and linked to the light using the operator chooser. 

When choosing the operator from the shop either the vopnet or the output node can be selected. If the vopnet is chosen and it contains multiple Output nodes then Arnold will use the first one it finds.

Creating Light Filters

In your chosen vopnet Tab-type (Custom > Light Decay / Light Blocker / Gobo / Barndoor) to create a light filter node. Connect the output of the light filter node to the Light Filter # parameter of the light output node. As one is connected another empty input will be added. It is not possible to use more than one gobo or barndoor filter on the same light.

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