Vray light question

[Smalerbi]

Hello,

I have been using Vray for as long as I can remember and I never got around to asking this question. When I'm working on an interior scene and place the Vray lights in the windows, I was always curious why the light dimensions never match up to the window size. For example, if I have a 6'x4' window, the Vray light will cover the entire window but the size will read 3'x2'. This also may be a related issue but I also notice I need to crank up the light values to insane numbers with vray lights and lights using IES files. I'm assuming this could be a system unit thing but I have no idea how to correct it.

Any suggestions would be appreciated

Thanks

Scott

[tashko.zashev]

Hi,

V-Ray rectangular light uses "Half-length" and "Half-width" parameters to control the size. Therefore you need to divide the real value (length/width) by "2".

[kosso_olli]

Now read careful, what the dialog for the size reads in the Vray light setting: HALF-length...

EDIT: Forget what I wrote, Tashko was faster.

[tricky]

Hi,

V-Ray rectangular light uses "Half-length" and "Half-width" parameters to control the size. Therefore you need to divide the real value (length/width) by "2".

Why is this?

[Smalerbi]

Hi,

V-Ray rectangular light uses "Half-length" and "Half-width" parameters to control the size. Therefore you need to divide the real value (length/width) by "2".

Thanks......that explains that but I'm with Richard.....why? Also, what about the light values....please see attached. This is an interior scene I worked on and if you check the power values of the lights in the soffit, they technically way out of whack but visually it looks correct. This has happened in all of my interior scenes. For some reason, I can never use the manufactured lighting specs because it does not produce enough light. I remember in Lightscape, I was able to put in the manufacture specs and it would produce a physically correct lighting scenario. So....what am I not doing correctly in Vray?

Thanks

Scott

[Morne]

Well that depends if your scene is setup correctly in the 1st place and your cam exposure. For example that jpg through the window should be a bit brighter almost overexposed

[Smalerbi]

Well that depends if your scene is setup correctly in the 1st place and your cam exposure. For example that jpg through the window should be a bit brighter almost overexposed

With regards to the jpg image, I agree, but it was important to showcase the views for this particular job so I had to fudge the background a bit. When you say, "Set up your scene correctly" Could you please be a bit more specific? My camera is set up pretty close to real world settings....f-stop, shutter....etc. Do the system units have anything to do with it?

Scott.

[voltron7]

Why is this?

I have also wondered about the reason behind this...no biggie though.

[grantwarwick]

power of 4? inverse 2?

[Sliver_Creations]

Why is this?

That's easy think of it as the following. If you have a square spot light 1 meter from a wall and it gives you a 1 by 1 meter square of illiminated wall. Now move the light to 2 meters you will now have a square of 2 by 2 meters. So the same amount of light covers an area 4 times a large so twice the range gives you 4 times less illumination per area.

[voltron7]

If we are strictly speaking in terms of the light icon's size in the viewport, why not just simplify things and use the full width and height measurements. Or rename the light sizes to something more complicated than WxH.