[Radiance-general] mkillum -ab 0 question

[Thomas Bleicher]

On Wed, Dec 14, 2011 at 8:39 AM, Marija Velickovic <maricanis at gmail.com>wrote:

>
> *I want to get completely black image with reflected light patch only, so
> I can sum images from various time moments during day/year and show light
> patch moving for some period of time.*
>
> To get image with specularly reflected light only:
> 1. I defined sky with sun only (no diffuse sky or ground sources)
> 2. Calculated mkillum -ab 0 -av 0 0 0 (l+ option) for my deflector surface
> 3. Used mkillum output in new octree as only light source (removed sun
> definition)
> 4. Calculated image with rpict -ab 0 -av 0 0 0
> Problem is that beside direct light patch inside  the test room, I still
> get some light on surfaces above/below my deflector surface.
>

To compare the effect of a new design with an existing situation you could
just create two images (before and after) and subtract the "before" image
from the "after".

Appart from that I think you should use a mirror material for your
reflector. If it's not a flat surface use a reasonable geometric
approximation. It will look different but probably will still give you the
right idea about the effect. If you are only interested in the direct
reflection of the sun (single virtual light source per mirror polygon) you
should be able to render the scene even if you have a lot of mirror
surfaces.

To eliminate the sky (direct or indirect) remove the sky and ground
definition from the sky file (you are already doing that).

If you are not set on a "black and white" footprint of the reflection you
could also use a coloured mirror (say red) and use only white/grey
materials. Your reflection will show as a red patch while direct sunlight
will still be white.

Regards,
Thomas
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