Basic question to ies-lights / fluorescent tube

[Kissling]

Hello,

I have a general question to ies-lights.
The brightness distribution in the room and the light intensity are saved in these files.
So far so good.
This suggests that the geometry is also included.
Question: Is it possible to create a fluorescent tube with an IES light?
If yes how?
And how can the emitting geometry be made visible so that glare effects can be generated?

Regards
Ronald

[sirio76]

I see no reason why you can't create a fluorescent tube using IES, however is much more convenient to use a tube geometry with a Vray Light material or even a simple Vray Area light for simulating something like LED stripes and similar.
If you use correct intensity values (something that may or may not be stored inside IES file) both the options will generate nice glare like any other light source.
Here for example I've used two simple area lights (one with a LED stripe texture): https://forums.chaosgroup.com/fileda...9&d=1633812047 and the glare is perfectly visible.

[Kissling]

Many thanks for your response.
OK, I think I have to dig a little deeper.
I would like to receive each light in the light mix as a single light so that I can adjust it after rendering and thus save time.

I would love to use geometry as a lightsouce.
Unfortunately, V-Ray 5 can't do geometry lights.

The use of an IES light was an idea because it creates very nice light distributions on the wall.
Maybe that's the wrong way to go.
Do you know an IES file with which I could test this?
Or which way would you suggest?

Regards Ronald

[sirio76]

You can use geometry as light source by applying a Vray Light material and you can even use it in Light Mix without issues
IES lights are no more accurate than any other light sources regarding light distribution, the difference between an IES and an area light is that the IES file simulate also the pattern of the light reflected by the light source body, but the falloff is still inverse square. For this reason I see no big benefit in using an IES for a neon or similar.
This week I'll release several free tutorial about Light Mix on my Youtube channel, in the mean while I've recorded a quick gif (I've used a simple sweep as geometry) :

[sirio76]

here is the file:

[Kissling]

Hello Sirio,

thaks for your answer.
Al this was known.
Anyway.
The problem for me is:
If you have more than 1 self illuminating lights, all of them are collectet together in only one Light-Mix Cannel "Self Ilumination"

Is there any way to display each polygonal Light in a seperate chanel in LightMix?
Regards Ronald

[sirio76]

As far as I know there is no way to get what you need, be sure to contact developers so that they give priority to mesh area lights (I think that are already planned for the future).
What you can do is something like this using cryptomatte, is not the same but at least you have some small control over the light:

[aleksandar.kasabov]

Hello Kissling,

We don't have the mesh light just yet, but it is on our to-do list and will be implemented in the future. Until then you could use the workarounds, that sirio76 mentioned above.