[Radiance-general] window glass modeling

[Lars O. Grobe]

Hi Milan!

>> It will still be useful to render some views (plan view, perspectives) to
>> understand what is going on. Artefacts due to ambient settings not adapted to
>> e.g. you fenestration become evident when you look at a splotchy image, but
>> may be difficult to understand from some few illuminances.
>
> Thank you for advice. This is useful.

As Marija wrote, you can also just put a grid of sensor points into the 
scene. The background of my proposal was that a rpict-generated image 
may be useful to track problems in the scene, even though the irradiance 
values you get would certainly be affected by the geometry added as a 
working plane (which is not necessary when using a grid as rtrace 
input). So if you take this approach, do not compare the results of a 
rendered image including work plane geometry to sensor point 
illuminances rendered without such geometry - they must be different. 
But look out for suspicous shadows, splotches, noise, gradients that 
look too smooth or not as smooth as you would expect it from the 
geometry. Do all the basic checks (Afternoon sun coming in from 
East...?) to find out whether the model is ok, this may help avoid a lot 
of trouble. For illuminance readings, you will have to remove the work 
plane geometry before running rtrace.

>> You need only one glass pane. Same as in real. The only pitfall is that,
>> without mkillum, you would get a lot of noise at acceptable ambient settings,
>> or never ending rendering times. So just use a mkillum surface at your glass
>> pane, and on the inner side of the blinds.
>
> I know that I have to use mkillum surface at my glass pane, I just forgot to
> write it. Thank you anyway. But, how can I use mkillum surface on the inner side
> of the blinds?

As long as the blinds are outside the glass, everything is fine and you 
can use the glass surface as an mkillum input. If you ever should have 
to render a model with blinds on the inner side of the window, it is 
important to remember that the mkillum pane has to be inside the 
complicated geometry to precalculte.

> Please, can you explain me this: "render illuminance on a work plane (maybe you
> put a desk surface into your model) using rpict -i".

As you may already know, rpict per default gives you an image according 
to choosen projection, which means it results in an array of luminance 
values. You may however use the -i switch to get an image showing 
irradiance values on the visible surfaces. Using falsecolor, you can get 
a quick idea on how illuminance is distributed over the surfaces of your 
scene.

Cheers, Lars.

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