Light passing through semi opaque material,

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Chuckie744
Posts: 5
Joined: Wed May 16, 2018 8:31 am

Light passing through semi opaque material,

Postby Chuckie744 » Wed May 16, 2018 8:40 am

Hi, I’m still feeling my way around LightUp and hope this not a frivolous question.
I’m trying to recreate the effect of how light is attenuated as it passes through semi opaque material such as sheer curtains. Using 100% opaque material clearly blocks sunlight as expected but using a semi opaque fabric, for example 50% opaque has the same effect on the suns attenuation as 0% opaque. It’s as though the material was not there at all.
Can anyone provide me with steps necessary to allow for attenuation of sunlight to simulate sheer curtains? Thank you.

skywlkrsnd
Posts: 12
Joined: Mon Mar 05, 2018 1:50 pm

Re: Light passing through semi opaque material,

Postby skywlkrsnd » Mon May 28, 2018 7:15 pm

I was able to reproduce this. The attached image shows three rooms, all with a light on the right side and a light meter grid on the left side.

The farthest right room has no material between the source light and the light meter grid.
The middle room as a material set to 25% opacity between the light and the light meter grid.
The farthest left room as a material set to 75% opacity between the light and the light meter grid.

The middle room does not show any light passing through to the opposite wall. But the farthest room does. Is this similar to what you're seeing?
Attachments
transparency test_lightup(no scene)_2018-05-28_1511.jpg
transparency test_lightup(no scene)_2018-05-28_1511.jpg (92.5 KiB) Viewed 573 times
Last edited by skywlkrsnd on Mon May 28, 2018 7:19 pm, edited 2 times in total.
Tim

skywlkrsnd
Posts: 12
Joined: Mon Mar 05, 2018 1:50 pm

Re: Light passing through semi opaque material,

Postby skywlkrsnd » Mon May 28, 2018 7:18 pm

In my previous test, the middle shapes were painted with the transparent materials on one side only.

Here's the same thing with painting the materials on both sides. Seems to do the trick.
Attachments
transparency test_lightup(no scene)_2018-05-28_1517.jpg
transparency test_lightup(no scene)_2018-05-28_1517.jpg (97.1 KiB) Viewed 573 times
Tim

Chuckie744
Posts: 5
Joined: Wed May 16, 2018 8:31 am

Re: Light passing through semi opaque material,

Postby Chuckie744 » Tue May 29, 2018 1:33 am

Thanks Tim, you’ve achieved a good result with attenuation and I’ve managed to replicate that myself in terms of modifying the overall intensity of light.
However I am still not able to produce shadow variations caused by a direct light source passing through sheers of varying opacity.
What I mean by that for example, is when sunlight streams in through full height windows with mullions, the shadows cast inside the room appear to not change regardless of whether the material of the sheer curtains is painted with 20%, 50%, 90% opaque material. The only visible difference occurs when the sheers are painted with 100% opaque material at which point, as expected, the shadows disappear.

skywlkrsnd
Posts: 12
Joined: Mon Mar 05, 2018 1:50 pm

Re: Light passing through semi opaque material,

Postby skywlkrsnd » Tue May 29, 2018 12:45 pm

Some follow up questions:
- Are your sheer curtains thin geometry or solid geometry?
- Do you have "Render both sides" checked or uncheck in LightUp preferences?
- Have you tried a LightUp light source instead of the sun? Does it yield the same effect?

Not sure if these will resolve anything; I'm just brainstorming.
Tim

Chuckie744
Posts: 5
Joined: Wed May 16, 2018 8:31 am

Re: Light passing through semi opaque material,

Postby Chuckie744 » Tue May 29, 2018 9:21 pm

These are good questions and hopefully, understanding the relevance of them will broaden my own knowledge, which is still in nappy stage.
The sheers were imported via the warehouse and the opacity was modified by painting both sides with material of a certain opacity.
Not sure about the difference between thin and solid geometry but given the curtains had thickness, rather than a simple 2D element, I’d answer that as solid geometry.
I have always checked the render both sides option as it has always yielded the result I’d expected so never found a need to uncheck it. Like so many options in light-up, I don’t understand what they do and am learning as I go.

bryansears
Posts: 22
Joined: Mon Dec 04, 2017 10:26 pm

Re: Light passing through semi opaque material,

Postby bryansears » Tue Jun 12, 2018 1:53 am

DId you ever find a solution to your problem?

Chuckie744
Posts: 5
Joined: Wed May 16, 2018 8:31 am

Re: Light passing through semi opaque material,

Postby Chuckie744 » Tue Jun 26, 2018 8:13 am

No I didn’t. I had some helpful advice but nothing seemed to work. It was absorbing too much time so I did a workaround and shifted the problem to the Too Hard basket. Thanks for asking.

bryansears
Posts: 22
Joined: Mon Dec 04, 2017 10:26 pm

Re: Light passing through semi opaque material,

Postby bryansears » Sat Jul 14, 2018 3:18 am

Chuckie, I do believe that support for this plug-in is not so robust!

Chuckie744
Posts: 5
Joined: Wed May 16, 2018 8:31 am

Re: Light passing through semi opaque material,

Postby Chuckie744 » Sat Jul 14, 2018 5:10 am

You could well be right. However I’m still amazed by some of the results that I’ve achieved thus far.
I do hope that in the not too distant future there may be a substantial update as even with my limited experience, there appears to be some annoying. recurring bugs.
In my humble opinion, the plug-in has too many features, most of which I’d never use. Concentrating delivering core features with fewer bugs would be smart thinking.


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