3Delight area lights wrong orientation

[vNicolini]

Version: Gaffer-1.4.0.0b6-windows
Third-party tools: Arnold 7.2.5.1 / 3Delight 2.9.76

Description

While reproducing an Arnold lightrig with 3Delight i've noticed that the area lights from 3Delight isn't matching orientation wise, they are inverted. To match Arnold's output the Two Sided plug needs to be checked.

Steps to reproduce

1. Create an aiQuadLight
2. Create a plane and assign a dlAreaLight shader to it
3. Link the xforms of the aiQuadLight to the dlAreaLigh plane and match all attributes applicable
4. Render the scene with both 3Delight and Arnold

See provided repro scene attached

DBG-1000_Lighting_v0001.zip

[gkocov]

While 3Delight doesn't have native area light primitives (the areaLight shader is basically an emissive surface shader that one can attach to any geom), long term it would be great in Gaffer to have a 3DL area quad light for user convenience that internally would pack a plane primitive with the areaLight shader assigned and associated with the Gaffer light sets, matching as much as possible the Arnold, Cycles and USD Gaffer lights.

In the meantime as a relatively simple workaround you can use a ReverseWinding node to invert the normals orientation of the dlAreaLight plane geo or use a USD rect light. I've uploaded the above test scene adapted to showcase the two workarounds.

DBG-1000_Lighting_v0002.zip

[johnhaddon]

long term it would be great in Gaffer to have a 3DL area quad light for user convenience

Long (or even short-medium) term, we're hoping to use the USD RectLight for this, and more generally to encourage the use of the USDLux lights in all renderers, rather than maintain support for lots of different renderer-specific lights. With that in mind, it would be great to get feedback on the usability of those in 3Delight (or Cycles/Arnold). I'm currently working on adding a few Arnold-specific extensions to the USD lights, and will be happy to do the same for other renderers.