[Radiance-general] Compute direct component from sky only

[nick devlin]

Thomas,

thanks for that. I had tried it in the past but rtrace returns values of  
zero!!

I was confused about this, until I remember that for a uniform, or  
overcast sky (the types I am testing), the sky is a glow source, which I  
believe is not tested in the direct calculation.
which means I am back to the drawing board.

I thought about subtracting the ambient values from the total illuminance  
values, but this is no help either as sky glow falls in the ambient file.

Any thoughts?

regards

nick


Message: 8
Date: Thu, 22 Sep 2005 11:36:57 +0200
From: Thomas Bleicher <tbleicher at arcor.de>
Subject: Re: [Radiance-general] Compute direct component from sky only
To: Radiance general discussion <radiance-general at radiance-online.org>
Message-ID: <8089AB3B-D9E9-4498-9B68-14F0188A1BB7 at arcor.de>
Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed


On 22.09.2005, at 10:00, nick devlin wrote:


> Dear All,
>  I am trying to calculate the direct light from the sky for a reference  
> grid within a number of rooms. I am sure there is a sophisticated manner  
> in which to achieve this, but I have cobbled together an approach in the  
> following way:
>  delete the ground source glow from the sky.rad description
> use rtrace to calculate the values for the points, but set -av 0 0 0 and  
> use a single material for all surfaces (except apertures!) which is  
> excluded from the ambient calculation using -ae.
>

You have to set "-ab 0" as well or ...


> There are some points within the rooms, which I am pretty certain do not  
> have a direct view of the skydome, and therefore should return a zero  
> value, but they do not.
>

... you get indirect contributions from the sky.

If I do understand the discussions on the list correctly you have to
take into
account _only_ direct components for ie. "Right of Light" and other
legal stuff.
In reality the indirect components do count as well.


Thomas