POV-Ray : Newsgroups : povray.advanced-users : Distance affects render speed? Server Time
29 Jul 2024 10:30:47 EDT (-0400)
  Distance affects render speed? (Message 1 to 6 of 6)  
From: Hugo
Subject: Distance affects render speed?
Date: 26 Apr 2002 13:39:32
Message: <3cc990d4$1@news.povray.org>
Hi, just a small question:

Why does light from a big distance slow down rendering? My guess: it's got
to do with the nature of floats. Is there anything I should know to keep an
optimal speed? Avoid big scale of numbers?

Someone posted a source with this light:
light_source { <1e4,3e4,1e4> rgb 1

I don't know what that location means, but changing it made me aware of this
thing.

Regards,
Hugo


Post a reply to this message

From: Jaime Vives Piqueres
Subject: Re: Distance affects render speed?
Date: 26 Apr 2002 13:54:41
Message: <3cc99460@news.povray.org>
Hugo wrote:

> Hi, just a small question:
> 
> Why does light from a big distance slow down rendering? My guess: it's got
> to do with the nature of floats. Is there anything I should know to keep
> an optimal speed? Avoid big scale of numbers?

 Do you have a sky_sphere on the scene? I ask because I had a similar 
experience, but the problem was that I placed my light_source outside the 
sky_sphere. 

-- 
Jaime Vives Piqueres

La Persistencia de la Ignorancia
http://www.ignorancia.org


Post a reply to this message

From: Warp
Subject: Re: Distance affects render speed?
Date: 26 Apr 2002 14:31:35
Message: <3cc99d07@news.povray.org>
Hugo <hua### [at] post3teledk> wrote:
> Why does light from a big distance slow down rendering? My guess: it's got
> to do with the nature of floats.

  Yeah, larger floats are slower to handle... ;)

  No, the true answer is that the farther away the light source, the longer
it takes to reach the object (why do you think that it takes about 8
minutes for light to travel the distance from the Sun to the Earth?).

  No, seriously.
  The value of a float has no effect on its speed.
  The most probable answer to your question has something to do with light
buffers. The light buffer algorithm works best when the objects are about
equally distributed all around the light source. If all the objects are
inside a very small area from the point of view of the light source, the
less efficient the light buffer algorithm is.

-- 
#macro N(D)#if(D>99)cylinder{M()#local D=div(D,104);M().5,2pigment{rgb M()}}
N(D)#end#end#macro M()<mod(D,13)-6mod(div(D,13)8)-3,10>#end blob{
N(11117333955)N(4254934330)N(3900569407)N(7382340)N(3358)N(970)}//  - Warp -


Post a reply to this message

From: Hugo
Subject: Re: Distance affects render speed?
Date: 26 Apr 2002 14:52:07
Message: <3cc9a1d7$1@news.povray.org>
>  Do you have a sky_sphere on the scene? I ask because I had a similar
> experience, but the problem was that I placed my light_source outside the
> sky_sphere.

Thanks, well, I don't have a sky_sphere and I thought it was impossible to
place anything outside it..?

Regards,
Hugo


Post a reply to this message

From: Hugo
Subject: Re: Distance affects render speed?
Date: 26 Apr 2002 14:54:59
Message: <3cc9a283$1@news.povray.org>
>   No, the true answer is that the farther away the light source, the
longer
> it takes to reach the object (why do you think that it takes about 8
> minutes for light to travel the distance from the Sun to the Earth?).

LOL !

>   The most probable answer to your question has something to do with light
> buffers. The light buffer algorithm works best when the objects are about
> equally distributed all around the light source. If all the objects are
> inside a very small area from the point of view of the light source, the
> less efficient the light buffer algorithm is.

Thanks, this was new to me.
That's probably the reason... Good to know.  :o)

Regards,
Hugo


Post a reply to this message

From: Jaime Vives Piqueres
Subject: Re: Distance affects render speed?
Date: 26 Apr 2002 15:08:38
Message: <3cc9a5b6@news.povray.org>
Hugo wrote:

> Thanks, well, I don't have a sky_sphere and I thought it was impossible to
> place anything outside it..?

  Ooops! Sorry, it was a home-made "sky sphere", with transparent pigments. 
That seems to be the reason for the slowdown in my case.

-- 
Jaime Vives Piqueres

La Persistencia de la Ignorancia
http://www.ignorancia.org


Post a reply to this message

Copyright 2003-2023 Persistence of Vision Raytracer Pty. Ltd.