[Radiance-general] Question of light sources vs glow material

[Lars O. Grobe]

Hi Chew Wei,

the difference is that there is no reasonable way to define the dome  
using light. Light is perfect for small intense sources. At every ray  
intersection, Radiance can efficiently test for light sources by  
sending a Ray to the source. This is more efficient then sending rays  
to random directions trying to find a source, which is the mechanism  
to treat a glow source. However, in the case of a sky dome, you would  
have to subdivide the source a lot or, if you have defined e.g.  
patches as light sources, you need to test a lot of these patches. For  
the typically rather smooth gradient of sky luminance this does not  
make sense in most cases compared to having a continous glow source  
with a gradient applied.

Cheers, Lars.

--
Dipl.-Ing. Architect Lars O. Grobe

On Jul 29, 2010, at 0:28, chang cw <solomoncw76 at gmail.com> wrote:

> Hi all,
> Would there be any differences
>  if i have a sky dome defined by a series of light sources ( with  
> the subtended FOV defined ) and one that is defined by a continuous  
> glow material ?
>
> Of course the main task is for daylighting applications .
>
> Cheers!
>
> CW
>
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