Vray light directional strength inconsistency between IPR and render

[seandunderdale]

Hi,

Im finding that vray rect lights behave differently in IPR and render when using the "directional strength" value. In the specular channel I get soft reflection in IPR, but in render I get crisp brighter reflections. Playing with this value is the only thing that seems to change the behavior. I have attached a scene.



Maya 2024.2
V-Ray 6 for Maya, update 2
(v6.20.00 from Feb 11 2024)

[seandunderdale]

Im finding the forum is super buggy when trying to upload images and zip files....Here is a link to a google drive instead...

https://drive.google.com/file/d/1ysA...ew?usp=sharing

[seandunderdale]

IPR render
https://drive.google.com/file/d/1lLJ...ew?usp=sharing

Progressive render (looks the same using bucket)
https://drive.google.com/file/d/1XpL...ew?usp=sharing

[hermit.crab]

Scaling of VRayLights is never a good idea. Use the U/V size parameters.

[seandunderdale]

Thanks for the reply. I went back and re-read the thread I thought that said XYZ scaling was fine now....it kind of says that, but also says its still not advisable. I did duplicate the light and set it up using U/V scale and it does render correctly, so I will amend my workflow. I do wish we had a view-port gizmo on lights as I find it was more intuitive to scale lights in the scene using the manipulator, than using the attribute editor window.

[SonyBoy]

Scaling of VRayLights is never a good idea. Use the U/V size parameters.

I've never fully understood why this is, and I also thought this was a thing of the past anyway. Can you explain why we should not scale light widgets directly, and why it's not possible for you to fix this? It really is a hindrance to lighting workflow and would obviously be much more artist friendly to be able to simply scale lights in the scene, rather than having to mess about with separate U and V values. Could you not at least even improve the accessibility of the UV values in some way, or "fake" widget scaling with some custom attributes so that we can directly work with light widgets in the scene.

[hermit.crab]

I did duplicate the light and set it up using U/V scale and it does render correctly, so I will amend my workflow.

I continued troubleshooting and found out that the issue is caused by a few factors, namely: Production rendering with camera motion blur and a scaled directional VRayLight within the camera group. I've logged it (internal bug-tracker id: VMAYA-12786) for dev investigation.

I've never fully understood why this is, and I also thought this was a thing of the past anyway. Can you explain why we should not scale light widgets directly, and why it's not possible for you to fix this?

Sometimes, when VRayLights are scaled the calculations get messed up. We've solved most such issues and as you can see above, the scenario for reproduction is not common.

Otherwise, I like the gizmo idea and have forwarded it to the product managers for assessment.