POV-Ray : Newsgroups : povray.binaries.images : i be stumped Server Time: 11 Dec 2018 15:20:37 GMT
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From: Jim Holsenback
Subject: i be stumped
Date: 23 Aug 2018 00:36:15
Message: <5b7e017f@news.povray.org>
well i'm kind of chasing my tail so i thought i'd ask for some guidance. 
i'm using radiosity and a very dim point light to get some shadow 
action. check out the lower left hand corner of the image. that's what 
i'm shooting for! why don't the other spheres have the same affect? 
other that the color there's no diff...the emission component is the 
same level for all the colors. is it more about the emission of the 
object or the surface that is showing the affect.


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From: Thomas de Groot
Subject: Re: i be stumped
Date: 23 Aug 2018 06:30:28
Message: <5b7e5484$1@news.povray.org>
On 23-8-2018 2:36, Jim Holsenback wrote:
> well i'm kind of chasing my tail so i thought i'd ask for some guidance. 
> i'm using radiosity and a very dim point light to get some shadow 
> action. check out the lower left hand corner of the image. that's what 
> i'm shooting for! why don't the other spheres have the same affect? 
> other that the color there's no diff...the emission component is the 
> same level for all the colors. is it more about the emission of the 
> object or the surface that is showing the affect.

Hum... Have you tried to switch the colours? It looks like the red 
spheres are subdued but still the emission is visible; blue is hardly 
visible at all. The green seems much brighter though. Make other spheres 
green too and see what happens.

-- 
Thomas


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From: clipka
Subject: Re: i be stumped
Date: 23 Aug 2018 10:16:24
Message: <5b7e8978$1@news.povray.org>
Am 23.08.2018 um 02:36 schrieb Jim Holsenback:
> well i'm kind of chasing my tail so i thought i'd ask for some guidance.
> i'm using radiosity and a very dim point light to get some shadow
> action. check out the lower left hand corner of the image. that's what
> i'm shooting for! why don't the other spheres have the same affect?
> other that the color there's no diff...the emission component is the
> same level for all the colors. is it more about the emission of the
> object or the surface that is showing the affect.

Looks to me like a radiosity setting issue, with too low sample density.

In the bottom left corner, by chance a sample was taken very close to
the base of the green... tron unicycle?... and picked up the emission
very nicely, while all other samples were taken comparatively far away
from the gizmos.

There are various knobs you might try tweaking here, but my personal bet
is that `error_bound` is set too high. You'll probably want a value of
0.5 or even lower. The default of 1.8 certainly won't cut it.

In reducing `error_bound` you may find that the result looks unnaturally
splotchy. If it is a general effect, try increasing `nearest_count`
and/or `count` to compensate. If instead (or after you adjust
`nearest_count` and/or `count`) the splotchiness is limited to nooks and
crannies, try reducing `minimum_reuse`.

Reducing `error_bound` (and, in some cases, increasing `count`) may also
introduce block-like artifacts. Those should be easy to fix by reducing
`pretrace_end`. A too high `pretrace_end` may also prevent changes to
`nearest_count` from being fully effective.


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From: Jim Holsenback
Subject: Re: i be stumped
Date: 23 Aug 2018 10:19:47
Message: <5b7e8a43$1@news.povray.org>
On 08/23/2018 02:30 AM, Thomas de Groot wrote:
> On 23-8-2018 2:36, Jim Holsenback wrote:
>> well i'm kind of chasing my tail so i thought i'd ask for some 
>> guidance. i'm using radiosity and a very dim point light to get some 
>> shadow action. check out the lower left hand corner of the image. 
>> that's what i'm shooting for! why don't the other spheres have the 
>> same affect? other that the color there's no diff...the emission 
>> component is the same level for all the colors. is it more about the 
>> emission of the object or the surface that is showing the affect.
> 
> Hum... Have you tried to switch the colours? It looks like the red 
> spheres are subdued but still the emission is visible; blue is hardly 
> visible at all. The green seems much brighter though. Make other spheres 
> green too and see what happens.
> 

yep tried that already!!! with them all green still only the lower left 
sphere?!? with them all red same thing .... lower left. i tried killing 
the point light and the emission from the hdr dome... same deal. i 
started getting results by jacking up the pigment component... red 
channel, blue channel etc... makes me think radiosity is the issue. i'm 
using defaults except the following:

gray_threshold 0
brightness 1
media on
normal on
count 1024


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From: clipka
Subject: Re: i be stumped
Date: 23 Aug 2018 10:27:29
Message: <5b7e8c11@news.povray.org>
Am 23.08.2018 um 12:19 schrieb Jim Holsenback:

> channel, blue channel etc... makes me think radiosity is the issue. i'm
> using defaults except the following:
> 
> gray_threshold 0
> brightness 1

Just for the records, those also happen to be the default values.


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From: Jim Holsenback
Subject: Re: i be stumped
Date: 23 Aug 2018 10:30:37
Message: <5b7e8ccd$1@news.povray.org>
On 08/23/2018 06:16 AM, clipka wrote:
> Am 23.08.2018 um 02:36 schrieb Jim Holsenback:
>> well i'm kind of chasing my tail so i thought i'd ask for some guidance.
>> i'm using radiosity and a very dim point light to get some shadow
>> action. check out the lower left hand corner of the image. that's what
>> i'm shooting for! why don't the other spheres have the same affect?
>> other that the color there's no diff...the emission component is the
>> same level for all the colors. is it more about the emission of the
>> object or the surface that is showing the affect.
> 
> Looks to me like a radiosity setting issue, with too low sample density.
> 
> In the bottom left corner, by chance a sample was taken very close to
> the base of the green... tron unicycle?... and picked up the emission
> very nicely, while all other samples were taken comparatively far away
> from the gizmos.
> 
> There are various knobs you might try tweaking here, but my personal bet
> is that `error_bound` is set too high. You'll probably want a value of
> 0.5 or even lower. The default of 1.8 certainly won't cut it.
> 
> In reducing `error_bound` you may find that the result looks unnaturally
> splotchy. If it is a general effect, try increasing `nearest_count`
> and/or `count` to compensate. If instead (or after you adjust
> `nearest_count` and/or `count`) the splotchiness is limited to nooks and
> crannies, try reducing `minimum_reuse`.
> 
> Reducing `error_bound` (and, in some cases, increasing `count`) may also
> introduce block-like artifacts. Those should be easy to fix by reducing
> `pretrace_end`. A too high `pretrace_end` may also prevent changes to
> `nearest_count` from being fully effective.
> 

your response wasn't here when i was following up to thomas ... but yep 
lowering nearest_count started getting close to expected results... a 
little splotchy but i think you've set me on the right path... danke


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From: Jim Holsenback
Subject: Re: i be stumped
Date: 23 Aug 2018 10:41:24
Message: <5b7e8f54$1@news.povray.org>
On 08/23/2018 06:27 AM, clipka wrote:
> Am 23.08.2018 um 12:19 schrieb Jim Holsenback:
> 
>> channel, blue channel etc... makes me think radiosity is the issue. i'm
>> using defaults except the following:
>>
>> gray_threshold 0
>> brightness 1
> 
> Just for the records, those also happen to be the default values.
> 
lol yes...i had them as placeholders...tweaking those. i /was/ already 
thinking it was radiosity related issue.


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From: clipka
Subject: Re: i be stumped
Date: 23 Aug 2018 11:34:26
Message: <5b7e9bc2@news.povray.org>
Am 23.08.2018 um 12:41 schrieb Jim Holsenback:
> On 08/23/2018 06:27 AM, clipka wrote:
>> Am 23.08.2018 um 12:19 schrieb Jim Holsenback:
>>
>>> channel, blue channel etc... makes me think radiosity is the issue. i'm
>>> using defaults except the following:
>>>
>>> gray_threshold 0
>>> brightness 1
>>
>> Just for the records, those also happen to be the default values.
>>
> lol yes...i had them as placeholders...tweaking those. i /was/ already
> thinking it was radiosity related issue.

Don't tweak those two - they're fine. Especially messing with
`gray_threshold` will only make the effect less colourful.


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From: Jim Holsenback
Subject: Re: i be stumped
Date: 25 Aug 2018 23:32:53
Message: <5b81e725@news.povray.org>
On 08/22/2018 08:36 PM, Jim Holsenback wrote:
> well i'm kind of chasing...

made some progress! here's what i ended up with for radiosity:

media on
normal off
count 512
error_bound 0.1
nearest_count 15
minimum_reuse 0.01

i'd like to maybe add a few more spheres but i'm having issues with my 
placement macro...a one point i had them all looking like the were 
worshiping the light source. at least now there's a bit or randomness. i 
need to get a few more things in order before i commit this to a beauty run


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From: clipka
Subject: Re: i be stumped
Date: 26 Aug 2018 09:16:16
Message: <5b826fe0$1@news.povray.org>
I think your sky dome is the wrong way round. Noticed it when text
reflected in the spheres seemed "forward" when it should appear
mirrored, but the sign in the background also gives it away, with the
text apparently right-aligned.


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