I'm creating a city scene and a plaza is surrounded on all four sides by 
skyscrapers. These are mostly tinned glass and so reflect a lot.

My problem is that my scene is taking years to render because of all the 
reflections .. the light is bouncing down the streets from building to 
building!

Now, when I look at skyscrapers in my RL city, this doesn't happen .. 
everything just appears darkish unless the sky is actually reflecting on it.

How do I get this to happen in POVRay?

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"Rick Measham" <rickm*at%isite.net.au> wrote in message 
news:42bb45a1$1@news.povray.org...
>
> My problem is that my scene is taking years to render because of all the 
> reflections .. the light is bouncing down the streets from building to 
> building!
>
> Now, when I look at skyscrapers in my RL city, this doesn't happen .. 
> everything just appears darkish unless the sky is actually reflecting on 
> it.
>
> How do I get this to happen in POVRay?

The global setting 'max_trace_level' will already limit it by default to 5 
bounces but maybe you could set that to just 3 instead and still not effect 
transparent surfaces.

If you aren't using variable reflection (both a minimum and a maximum value 
together) yet maybe give that a try, so that the reflections diminish at 
various angles of view or incidence.

And, after saying all that, I almost forgot about the exact phenomenon you 
seem to have told of-- 'reflection_exponent', or as it is used now, just the 
word exponent with a value less than one and nearer to zero which reflects 
less of the darker things and so leaving brighter things to remain instead. 
At least I think this might be the best advice of the three choices I 
mentioned here, but I'm not sure how it'll effect render time. Maybe 
somebody else knows better than I do (no surprise, if so).

Bob Hughes

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Rick Measham nous apporta ses lumieres en ce 2005-06-23 19:28:
> I'm creating a city scene and a plaza is surrounded on all four sides by 
> skyscrapers. These are mostly tinned glass and so reflect a lot.
> 
> My problem is that my scene is taking years to render because of all the 
> reflections .. the light is bouncing down the streets from building to 
> building!
> 
> Now, when I look at skyscrapers in my RL city, this doesn't happen .. 
> everything just appears darkish unless the sky is actually reflecting on 
> it.
> 
> How do I get this to happen in POVRay?
Have a lower value for your reflection like reflection 0.5, never use reflection 1. In
the 
global_settings{...} set a slightly larger value for adc_bailout, like 1/128 to 1/64
A sample texture for your reflective windows can help to give you a more specific
suggestion.

Alain

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> > Now, when I look at skyscrapers in my RL city, this doesn't happen ..
> > everything just appears darkish unless the sky is actually reflecting on
> > it.

> Have a lower value for your reflection like reflection 0.5, never use
reflection 1.

This tip combined with making the sky significantly brighter than the
buildings will probably get the proper effect. I would try a lower
reflection value like 0.3 or so to get the building reflections as dark as
you think they should be, and then play with the sky brightness to make it
look right. It might be tricky to do this while avoiding a blindingly white
sky; the buildings themselves could be darkened to help avoid that.

 - Slime
 [ http://www.slimeland.com/ ]

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