[Radiance-general] About lamp color

[Thomas Bleicher]

On 26.09.2005, at 04:23, Huangwx at kyotoUniv. wrote:

> Dear all:
>
> I want to simulate different appearences of an interior space in  
> which the color of the fluorescent ceiling lamp varies (white or  
> warm color). There is another light source in the room, which is a  
> stand lamp with an incandescent bulb.
>
> In the book Rendering with Radiance, it is mentioned that the eyes  
> of human will adapt to the lampcolor, so it is safe to use white  
> lamp in simulation.

This is only true if you have only _one_ type of lamp. You should chose
the right type for each lamp if you plan to mix them in one environment.

> But actually people do feel different in space with different lamp  
> color. So is it possible for people to evaluate the interior space  
> with different lamp color via rendered images?

People will _feel_ different in different lighting situations. But this
is AFAIK only a small factor if you try to calculate ie. illuminance at
workplaces in an office. I think it is very difficult (if not  
impossible)
to decide about the effects of a chosen lamptype based on a small image
displayed on a (probable uncalibrated) monitor.

What you can do is estimating the difference between two designs. But I
don't think there are fixed criteria for this.

> If so, what are the lamp colors I should use? and what are the  
> parameters should I use in pfilt?

According to the man page you're looking for the "-t" option. The
table used for the lookups by default is called "lamp.tab" in the
base directory of your RAYPATH.

The first column in this file are the patterns Radiance knows about
by default. If you have more detailed information about your lamps
you can create your own lookup table and use the "-f" option in
pfilt to specify your table. See the comments at the top of lamp.tab.

An example would be:

     pfilt -t "warm white" neutral.pic > warm.pic

If you use a type that's not listed in the table pfilt will tell
you about it.

I think you have to start with a white balanced image or the results
will be usefull. I tried it on my benchmark pics and the "warm" filtered
image turned out blue ...

HTH,

Thomas