Issue: Light value wrong scaled by scaling the light

[Micha]

I rendered a train interior with a long rectangular light over the whole ceiling of the car. The lighting setup was perfect. Then I had to attach a monitor to the ceiling and I had to cut the light in half lengthwise and place it in front of/behind the ceiling monitor. The light setup was now far too bright.

Please disable the automatic scaling of the light value or allow the user to switch off the automatic change. It does not work.

Interestingly, the light value is only “scaled” when you scale the light in the viewport, but if you adjust the u size value in the light parameters, the light value is retained and everything looks fine. Attached my test scene.

Best-
Micha

[iva_mancheva]

Hello Micha,

Thank you for the feedback.

The way it is currently done is in order to have consistency between V-Ray and Rhino rectangular lights, because the Rhino Rectangle light's intensity is a function of its area. When you scale the V-Ray Rectangle light in the viewport -> its intensity in gets adjusted in V-Ray. When you change its U and V Size in Asset Editor -> its intensity gets adjusted in Rhino (in Rhino's lights panel).
Keeping a consistent intensity between Rhino and V-Ray helps for achieving similar results between Rhino Rendered view and V-Ray and also Enscape and V-Ray.

Kind regards,
Iva

[Micha]

iva_mancheva

I did a few more tests and we seem to have several problems here.

(a) If I enlarge the light with _Scale1D, the size in the V-Ray light parameters remains constant. However, if I grab the light by a handle in the viewport and enlarge it, the size of the V-Ray parameters is adjusted. It's a bug.

(b) If I have a light surface with 1000W and illuminate a table and halve its light surface and then hang it twice over the table so that the same surface is illuminated again, then I do not need two surfaces with 2000W (together 4000W) but 2x500W. The power per light source does not have to be doubled but halved so that the total power remains constant.

(c) In practice, however, it is not the power that is used but the luminosity. If I place a luminous surface over a table, halve it and hang it up twice next to each other, then the luminosity must remain constant.

Please deactivate the scaling of the light value or at least allow it to be deactivated at VfR Configuration , because it only causes trouble.

[javierrentas]

I agree with Micha.
The new light behavior does not make sense. I don't mind if you have the scale behavior on the default unit, but when I'm using Lumens or Watts I would like to keep the same power no matter the size of the light.
If I have a 10" flashlight that produces 1000 lumens and another 2" flashlight that produces 1000 lumens of light, I should have the same illumination no matter the size of the flashlight.
Please bring the old behavior to the lights when using watts or lumens. used.
It is very annoying and unpredictable that when you scale the light the intensity changes.