-aa and -ar parameter

Hi Radiance Community,

I have a quick question regarding the -aa and the -ar parameter settings:
In the radiance book and several tutorials it is written, that those parameters are controlling the "sphere of influence" of the pixels in a picture. But how do these parameters influence rtrace simulations, where I don't have a picture but sensor points?

Thanks and happy simulations
Matthias

Hi Matthias,

the "sphere of influence" relates to the resolution of the ambient cache, not a picture. -ar defines the initial resolution, -aa gives a criteria when to refine. The ambient cache aims at reducing the calculation of illuminance on surfaces in the diffuse-indirect calculation. It is enabled in rtrace and rpict as a default, but not in rcontrib.

Cheers, Lars.

···

Hi Radiance Community,

I have a quick question regarding the �aa and the �ar parameter settings:

In the radiance book and several tutorials it is written, that those parameters are controlling the �sphere of influence� of the pixels in a picture. But how do these parameters influence rtrace simulations, where I don�t have a picture but sensor points?

Thanks and happy simulations

Matthias

Yes -- just a minor wording correction. The -ar parameter sets the minimum ambient value spacing for full-accuracy, which is the specified parameter divided into the octree size. You can determine the octree size using the getinfo -d command on the octree, and it is reported as the fourth number in world distance units.

If you want there to be no limit to the minimum ambient value spacing, you can set -ar 0.

If you set -aa 0, you turn off the ambient cache and get a straight Monte Carlo path tracing method. This is sometimes preferable if you are computing just a few values in rtrace. (With -aa 0, the -ar settings has no effect.)

Cheers,
-Greg

···

From: "Lars O. Grobe" <[email protected]>
Subject: Re: [Radiance-general] -aa and -ar parameter
Date: January 20, 2016 3:39:46 AM PST

Hi Matthias,

the "sphere of influence" relates to the resolution of the ambient cache, not a picture. -ar defines the initial resolution, -aa gives a criteria when to refine. The ambient cache aims at reducing the calculation of illuminance on surfaces in the diffuse-indirect calculation. It is enabled in rtrace and rpict as a default, but not in rcontrib.

Cheers, Lars.

Hi Radiance Community,

I have a quick question regarding the –aa and the –ar parameter settings:
In the radiance book and several tutorials it is written, that those parameters are controlling the “sphere of influence” of the pixels in a picture. But how do these parameters influence rtrace simulations, where I don’t have a picture but sensor points?

Thanks and happy simulations
Matthias