[Radiance-general] increase resolution: BAM! fall off the end of the universe

[Georg Mischler]

George Michaelson wrote:

>  I did a kitchen with a mix of off-white and brushed steel
> aluminimum surfaces. I found that the amount of colour picked up by
> 'gloss' surfaces was increadibly high, but if I didn't select off-whites
> for detailed surfaces like tongue-and-groove wood, I got huge brightspots
> which wiped out the image unless I wound back the lightbulbs to 5 watt
> railway specials.

Did you notice that you can change the "exposure" to which the
final image is displayed? It has a very similar effect to the
combination of shutter speed and iris opening in a photo camera.
The pcond program mentioned by Peter is just another step beyond
that, which also takes some physiological properties of the human
eye into account, that may depend on the absolute brighness levels.

It could also be that you made your surfaces too glossy. Most people
greatly overestimate the amount of gloss in their visual environment.
In reality, gloss levels for non-metallic surfaces are typically
way below 5% (rather around 1 - 2%).


> I know that the chrome tap is reflecting part of a
> perfectly rendered image of the lightbulb onto every shiny surface within
> a 40 foot radius, but now I'm over 40 I can't see those little images
> unless I stand real close. Does radiance have to render them? isn't
> there some middle ground where it does high definition for some things
> but not others?

It's called pixel resolution.
If you render a picture where the tap is three pixels wide and two
pixels high, then I'm pretty sure you won't recognize the bulb that
is theoretically reflected in its surface. If the tap fills half
of your image, then you probably *want* to recognize the reflected
bulb, and given the right distance, you certainly will. But even
when the final image doesn't show a recognizable mirror image of the
bulb, you still want to notice the sparcle of the reflection, so
there is really no other useful "middle ground" here.

Note btw., that the surrounding surfaces will *not* see a perfect
mirror image, unless you use the "mirror" material for the tap,
which you shouldn't. If you use just a shiny metal, then the diffuse
calculation from other nearby surfaces will hit the tap at most once
or twice, which isn't enough for an exact reflection. Only surfaces
that are very close will again see more, simply because the tap fills
a significant part of their surrounding space.

Btw: In real live, just because your eyes don't want to resolve
that mirror image anymore, doesn't mean that they don't receive
the information about it. If you want to simulate that effect with
Radiance, you can simply apply a soft blur to the final image... ;)


> (I am not a professional. I do not depend on this software. If you do,
>  and need it to remain pure, I don't disagree.

Yes, we do indeed! (at least for a reasonable definition of "pure")


-schorsch

-- 
Georg Mischler  --  simulations developer  --  schorsch at schorsch.com
+schorsch.com+  --  lighting design tools  --  http://www.schorsch.com/