Ambient file Q's

I rendered a series of images with -ad 2048 -as 1024 -ar 52 -af file.amb
(taking many hours to render)
They came out splotchy, so I increased -ad 4096 -as 2048 -ar 200 -af
file.amb (building upon the same data)
I expected it to take quite a while to render, but they took ~ 5 to 10
minutes and I saw no real improvement
my question is the nature of the ambient file..
If I start it with a lower quality, can I improve it? Or is it similar to
trying to "upres" a Photoshop from 300 dpi to 600dpi

judging by my results, this seems to be the case

Thanks

Rob F

Fitzsimmons, Rob wrote:

I rendered a series of images with -ad 2048 -as 1024 -ar 52 -af file.amb (taking many hours to render)
They came out splotchy, so I increased -ad 4096 -as 2048 -ar 200 -af file.amb (building upon the same data)
I expected it to take quite a while to render, but they took ~ 5 to 10 minutes and I saw no real improvement
my question is the nature of the ambient file..
If I start it with a lower quality, can I improve it? Or is it similar to trying to "upres" a Photoshop from 300 dpi to 600dpi

Hi Rob,

I'm assuming you used rpict directly, and not rad? Anytime you change the rendering parameters you have to delete the ambient cache. Rad does this for you automatically. My guess is that you didn't do that, so there's the reason for both the speedy rendering and the negligible difference in image quality avan after doubling your ambient parameters.

So no, as I understand it, an ambient file seeded under lower quality settings will not improve when you re-run with higher settings. You must start over.

As for the splotchies, maybe some more detail about your model would help us troubleshoot that, or maybe a sample image?

···

----

      Rob Guglielmetti

e. [email protected]
w. www.rumblestrip.org

Hi Rob,

I remember having the same thought when I was learning radiance (which I am still learning by the way). Unfortunately, you cannot reuse an ambient file in this manner where you progressively refine the parameters and thus refine the ambient data. Generally, if you change the ambient parameters then you need to start off with a fresh ambient file. The one note here is that it is possible to "relax" certain of the parameters after first doing an overture calculation to fill the ambient cache. The -aa, -ad and -as parameters can be reduced after the overture calculation. For example, just looking at the ambient parameters:

pass 0 (overture)
-ab 2 -ar 200 -ad 4096 -as 2048 -aa .15

pass 1
-ab 2 -ar 200 -ad 2048 -as 1024 -aa .25

Note that the overture calculation is performed by running rpict on a small image size (64x64 for example) and discarding the image output. The point is to populate the ambient file with data. Rendering with Radiance has further information on this in John Mardaljevic's chapter (6) on Daylighting Simulation.

-Jack de Valpine

Fitzsimmons, Rob wrote:

···

I rendered a series of images with -ad 2048 -as 1024 -ar 52 -af file.amb (taking many hours to render)
They came out splotchy, so I increased -ad 4096 -as 2048 -ar 200 -af file.amb (building upon the same data)
I expected it to take quite a while to render, but they took ~ 5 to 10 minutes and I saw no real improvement
my question is the nature of the ambient file..
If I start it with a lower quality, can I improve it? Or is it similar to trying to "upres" a Photoshop from 300 dpi to 600dpi

judging by my results, this seems to be the case

Thanks

Rob F

--
# John E. de Valpine
# president
#
# visarc incorporated
# http://www.visarc.com
#
# channeling technology for superior design and construction

Rob Guglielmetti wrote:

So no, as I understand it, an ambient file seeded under lower quality
settings will not improve when you re-run with higher settings. You
must start over.

More precisely, you need a new ambient file after one or
several of the following parameters has been changed:

-av -ab -aa -ad -as -ar

-schorsch

···

--
Georg Mischler -- simulations developer -- schorsch at schorsch com
+schorsch.com+ -- lighting design tools -- http://www.schorsch.com/

Thanks
That explains it - I'll delete the amb file

I'm assuming you used rpict directly, and not rad? Anytime you change
the rendering parameters you have to delete the ambient cache. Rad does
this for you automatically. My guess is that you didn't do that, so
there's the reason for both the speedy rendering and the negligible
difference in image quality avan after doubling your ambient parameters.

Actually, I did it through rad with Render= options

So no, as I understand it, an ambient file seeded under lower quality
settings will not improve when you re-run with higher settings. You
must start over.

As for the splotchies, maybe some more detail about your model would
help us troubleshoot that, or maybe a sample image?

here it be
http://www.geocities.com/rastermon/Sonti7_GR.html

···

-----Original Message-----
From: Georg Mischler
To: [email protected]
Sent: 1/6/2004 1:12 PM
Subject: Re: [Radiance-general] Ambient file Q's

More precisely, you need a new ambient file after one or
several of the following parameters has been changed:

-av -ab -aa -ad -as -ar

-schorsch

--
Georg Mischler -- simulations developer -- schorsch at schorsch com
+schorsch.com+ -- lighting design tools -- http://www.schorsch.com/
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Fitzsimmons, Rob wrote:

As for the splotchies, maybe some more detail about your model would
help us troubleshoot that, or maybe a sample image?

here it be
http://www.geocities.com/rastermon/Sonti7_GR.html

What's at the top of that stair? A skylight? Window? Portal into another dimension? If it's one of the first two, I recommend using illums for the distribution of your luminous areas. That will help a great deal.

···

----

      Rob Guglielmetti

e. [email protected]
w. www.rumblestrip.org

Fitzsimmons, Rob wrote:

As for the splotchies, maybe some more detail about your model would
help us troubleshoot that, or maybe a sample image?

here it be
http://www.geocities.com/rastermon/Sonti7_GR.html

What's at the top of that stair? A skylight? Window? Portal into
another dimension? If it's one of the first two, I recommend using
illums for the distribution of your luminous areas. That will help a
great deal.

There is a second floor with 3 skylights
Here are QTVR's of several places in the house
http://www.geocities.com/rastermon/June21_Overcast.html

I think with the spiral staircase going though the opening would make it
difficult to create an illum polygon at that opening

Rob

Fitzsimmons, Rob wrote:

There is a second floor with 3 skylights
Here are QTVR's of several places in the house
http://www.geocities.com/rastermon/June21_Overcast.html

I think with the spiral staircase going though the opening would make it difficult to create an illum polygon at that opening

But even moving the "direct" light sources to a point closer to the scene (meaning put the illum impostors at the skylights & windows) should help things. But you will probably also have to increase -ad -ar -aa too.

···

----

      Rob Guglielmetti

e. [email protected]
w. www.rumblestrip.org