ID 248387 - Arnold light filter shaders break during Live Renders when light is included in Live Render Updates Working Set

Problem summary
The effects of Arnold light filters (e.g. barndoors) aren’t visible in a Live Render if the light that has the filter applied is included in the Live Render Updates Working Set.
When the light is not included in the Working Set, the render is correct and also updates correctly when moving the camera etc.

Customer reported version
Katana 2.5v4 and 2.1v1
KtoA 1.1.1 and 1.0.7

Customer reported platform
CentOS 6.8

Steps to reproduce

1. Open the attached example scene. Alternatively, open the Hello Pony example scene for Arnold under Help > Example Projects and add an additional arnoldLightFilterShader to the light in the GafferThree. Set the bardoor_top_left and barndoor_top_right settings to 0.5.
   
   

   

   
   
   

2. Start a LiveRender from the GafferThree node. The resulting image looks exactly like a preview render and updates correctly with the light filter when moving the camera.
   
   

3. Click the checkbox in the Live Render Updates column next to the light in the scene graph to trigger live render updates when making changes to the light. Alternatively, right-click on the checkbox next to the gaffer and choose ‘Included with Children’.
   
   

   

   
   
   Result: The effect of the light filter disappears in the live rendered image.

Workaround
Leave the Live Render Updates unchecked for the light and stop and start the live render after changes have been made.

Reproduced by support
Katana 2.0v1, 2.0v5, 2.1v1, 2.1v5, 2.5v1, 2.5v4 RHEL 6

Expected behaviour
The light filter should be affecting the render whether the light is included in the Live Render Updates Working Set or not.

Actual behaviour
The light filter is not taken into account in the render when the light is included in the Working Set.