Radiance "blotching" with translucent material

Hi all!

I hope I have the right term here, but I am having some issues with "blotching", i.e. circular patches in the rendered images (see below).

I am wondering if someone here knows how to set the radiance parameters to get rid of blotching. To add another level of complexity to my problem, I am running simulations with a translucent material with the following properties:

void trans testTrans

7 0.478 0.478 0.478 0.000 0.010 0.178 0.635

I have had no issues with the renderings when I use clear glazing, as seen on this image:

However the blotching-issue becomes very noticeable when I introduce translucent glazing into the scene:

For the two above cases I used the following parameters:

_av_ is set to 0

xScale is set to 2

_ab_ is set to 6

_dc_ is set to 0.5

_aa_ is set to 0.2

_ad_ is set to 2048

_st_ is set to 0.5

yScale is set to 2

_ps_ is set to 4

_ar_ is set to 64

_as_ is set to 2048

_ds_ is set to 0.25

_pt_ is set to 0.1

_dr_ is set to 1

_pj_ is set to 0.9

_dp_ is set to 256

_dt_ is set to 0.25

_lr_ is set to 6

_dj_ is set to 0.5

_lw_ is set to 0.01

I ran another test with increased Radiance parameters and got the following output:

with the following parameters:

_av_ is set to 0

xScale is set to 6

_ab_ is set to 6

_dc_ is set to 0.75

_aa_ is set to 0.1

_ad_ is set to 4096

_st_ is set to 0.15

yScale is set to 6

_ps_ is set to 2

_ar_ is set to 128

_as_ is set to 4096

_ds_ is set to 0.05

_pt_ is set to 0.05

_dr_ is set to 3

_pj_ is set to 0.9

_dp_ is set to 512

_dt_ is set to 0.15

_lr_ is set to 8

_dj_ is set to 0.7

_lw_ is set to 0.005

Although the second blotching case is much better than the first, it is still very bad for hours when the sun is lower in the sky. The above images are rendered for a clear sky at 18:00 in Germany in a West-facing room.

Sorry for the long post! Can someone help?

Kind regards,
Örn

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Replies to This Discussion

Permalink Reply by Mostapha Sadeghipour Roudsari on June 12, 2015 at 10:58am

Hi Örn,

This is a great question for Radiance's email list. If they can't help you there, which I'm pretty sure they will, I will be happy to take on this one.

It can be both because of the material definition or radiance parameters. I assume you have already checked this document (http://radiance-online.org/community/workshops/2010-freiburg/PDF/Da...). If you haven't then you should.

Permalink Reply by Örn Erlendsson on June 14, 2015 at 4:46am

Thanks Mostapha, I'm familiar with the document. I also posted my question on the Radiance email list and received answers yesterday. I will try their suggestions and report back.

Permalink Reply by Örn Erlendsson on June 15, 2015 at 9:07am

Hi Mostapha, would it be possible to add an optional input to the RadianceParameter component that would allow you to manually change the parameters which are currently automatically assigned by the component? For example:

I would like to try to edit some of these parameters to fix my blotching issue :)

Permalink Reply by Mostapha Sadeghipour Roudsari on June 21, 2015 at 5:00pm

Yes! It is definitely possible and looks like a great idea. What do you think about accepting a string instead of another component. I just assume if you are an advance user you should be comfortable with typing something like: -av 0 -dc 0.75 -st 0.15 -ps 2

Then the component can parse in the values and we avoid a pretty huge component. Let me know your thoughts on this.

Permalink Reply by Örn Erlendsson on June 22, 2015 at 3:17am

I think that is an excellent idea Mostapha. It serves the same purpose while avoiding unnecessary confusion for those that have less understanding.

Permalink Reply by Mostapha Sadeghipour Roudsari on June 22, 2015 at 5:56am

Here you go! I just committed the new version to github. Let me know if you find any bugs.

Permalink Reply by Örn Erlendsson on June 24, 2015 at 1:28am

Thanks Mostapha!

It works like a charm :)

Permalink Reply by Örn Erlendsson on June 22, 2015 at 4:02am

It took me a couple of minutes to understand, so in case anyone else needs help understanding how the A-parameters are calculated in the transMaterial component, see the following image: