Radiance -av setting

Dear all, I'm playing with the settings in Radiance. I've noted
something that I don't get. Attached are two draphs of DF in a room for
various numbers of ambient bounces (1-4). The top chart (ahigh1-4.opt)
is without an ambient value turned on while the bottom chart
(bhigh1-4.opt) is with an ambient value of 0.28 applied.

Why does the illuminance calculated invert at the back of the room( -ab
1 is the highest) when we give an ambient value? Surly all values
should be altered by the same amount?

I have also run the calculation for no ambient bounces and without a sky
description. In this case a flat graph is created (i.e. all points see
exactly the same illuminance). This is what I would have expected to
see....all points raised by a factor related to the -av setting.

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Hi Erik,

I think the difference is due to the fact that points closer to the window see more of the sky directly, whose value is unaffected by the -av setting. Towards the back of the room, more rays encounter opaque surfaces, where -av does matter.

-Greg

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From: "Erik Moore" <[email protected]>
Date: August 30, 2008 3:53:39 AM PDT
Dear all, I’m playing with the settings in Radiance. I’ve noted something that I don’t get. Attached are two draphs of DF in a room for various numbers of ambient bounces (1-4). The top chart (ahigh1-4.opt) is without an ambient value turned on while the bottom chart (bhigh1-4.opt) is with an ambient value of 0.28 applied.

Why does the illuminance calculated invert at the back of the room( -ab 1 is the highest) when we give an ambient value? Surly all values should be altered by the same amount?

I have also run the calculation for no ambient bounces and without a sky description. In this case a flat graph is created (i.e. all points see exactly the same illuminance). This is what I would have expected to see….all points raised by a factor related to the –av setting.

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