POV-Ray : Newsgroups : povray.binaries.programming : povr render 'optics.pov' Server Time: 28 Sep 2020 00:15:40 GMT
  povr render 'optics.pov' (Message 1 to 7 of 7)  
From: jr
Subject: povr render 'optics.pov'
Date: 15 Aug 2020 15:25:00
Message: <web.5f37fd6ba57451a94d00143e0@news.povray.org>
hi,

an unrelated thread made me render the 'scenes/advanced/optics.pov' file.  with
'povr' I get a strange "band" in the lower part of the image.  attached.


regards, jr.


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Attachments:
Download 'povroptics.png' (210 KB)

Preview of image 'povroptics.png'
povroptics.png


 

From: Le Forgeron
Subject: Re: povr render 'optics.pov'
Date: 15 Aug 2020 15:52:30
Message: <5f3804be@news.povray.org>
Le 15/08/2020 à 17:21, jr a écrit :
> hi,
> 
> an unrelated thread made me render the 'scenes/advanced/optics.pov' file.  with
> 'povr' I get a strange "band" in the lower part of the image.  attached.
> 
> 
> regards, jr.
> 

Only for povr, at least hgpovray38 is clear of such noise, and so I
presume official master (3.8) too.


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From: jr
Subject: Re: povr render 'optics.pov'
Date: 15 Aug 2020 16:15:00
Message: <web.5f3808df37c3ceb74d00143e0@news.povray.org>
hi,

Le_Forgeron <jgr### [at] freefr> wrote:
> Le 15/08/2020 à 17:21, jr a écrit :
> > an unrelated thread made me render the 'scenes/advanced/optics.pov' file.  with
> > 'povr' I get a strange "band" in the lower part of the image.  attached.
>
> Only for povr, at least hgpovray38 is clear of such noise, and so I
> presume official master (3.8) too.

yes, the alpha.10064268 output is ok.  have not yet installed 'bigarade' on this
machine, so good to know, thanks.


regards, jr.


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From: William F Pokorny
Subject: Re: povr render 'optics.pov'
Date: 15 Aug 2020 16:35:10
Message: <5f380ebe$1@news.povray.org>
On 8/15/20 11:21 AM, jr wrote:
> hi,
> 
> an unrelated thread made me render the 'scenes/advanced/optics.pov' file.  with
> 'povr' I get a strange "band" in the lower part of the image.  attached.
> 

Thanks jr (and Jerome)!

I see it too in all my recent povr versions. It was OK in versions early 
this year, so something I've done between then and early July.

I'll do a binary search - compile/run through my commits to find the 
commit causing the problem. FYI. No photons required to see it.

(jr, If you are looking for a scene with a parabolic mirror I recall 
Warp doing one some years ago which he posted. I thought had a copy 
somewhere, but I cannot find it at the moment. He might have used a 
polynomial for the shape.)

Bill P.


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From: jr
Subject: Re: povr render 'optics.pov'
Date: 15 Aug 2020 17:30:00
Message: <web.5f381ac537c3ceb74d00143e0@news.povray.org>
hi,

William F Pokorny <ano### [at] anonymousorg> wrote:
> On 8/15/20 11:21 AM, jr wrote:
> > an unrelated thread made me render the 'scenes/advanced/optics.pov' file.  with
> > 'povr' I get a strange "band" in the lower part of the image.  attached.
>
> Thanks jr (and Jerome)!

no sweat.  :-)

> ...
> (jr, If you are looking for a scene with a parabolic mirror I recall
> Warp doing one some years ago which he posted. I thought had a copy
> somewhere, but I cannot find it at the moment. He might have used a
> polynomial for the shape.)

that should probably be addressed to 'ttyUSB0'.  I was simply curious, following
Le Forgeron's reply to him/her.


regards, jr.


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From: William F Pokorny
Subject: Re: povr render 'optics.pov'
Date: 15 Aug 2020 18:16:43
Message: <5f38268b$1@news.povray.org>
On 8/15/20 12:35 PM, William F Pokorny wrote:
> On 8/15/20 11:21 AM, jr wrote:
...
> 
> I see it too in all my recent povr versions. It was OK in versions early 
> this year, so something I've done between then and early July.
> 
> I'll do a binary search - compile/run through my commits to find the 
> commit causing the problem. FYI. No photons required to see it.
> 

I broke the checker pattern on March 29th. ;-)

---
There has been a defined EPSILON value floating around in the code for a 
long time. Over the years it sort of got used any time folks had the 
thought, "I need an epsilon value." All to often it was (at 1e-10) a 
non-optimal value to use.

I've been cleaning these up; mostly breaking them into two buckets after 
determining what I thought good values numerically while doing my solver 
work. A treat this as zero epsilon and a good supportable intersection 
depth tolerance. The former I called gkDBL_epsilon which is a little 
larger than the C++ DBL_epsilon macro value and the other is called 
gkMinIsectDepthReturned(1).

When I updated EPSILON in the checker pattern, I used gkDBL_epsilon when 
I should've used gkMinIsectDepthReturned. Yes, this is an intersection 
with a plane, low order and more accurate - it was mostly working 
anyway. The actual supportable value is certainly between the two values 
I settled on. But, going with the standard gkMinIsectDepthReturned in 
checker unless something 'else' breaks.

Aside: Yes, sometimes you really need somewhat unique 'epsilon' values. 
When I was cleaning up the tiling patterns for isosurface use, I ran 
across a collection of such values where someone had commented that a 
C++ macro should perhaps be used. But in testing each, every one of 
those needed to be what they were to the order of magnitude. Jerome had 
done his homework! :-)

Anyway, thanks again for spotting this / testing.

Bill P.


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From: jr
Subject: Re: povr render 'optics.pov'
Date: 15 Aug 2020 19:00:00
Message: <web.5f38301837c3ceb74d00143e0@news.povray.org>
hi,

William F Pokorny <ano### [at] anonymousorg> wrote:
> ...
> I broke the checker pattern on March 29th. ;-)
> ...
> When I updated EPSILON ...  it was mostly working anyway. ...

:-)

> ...
> Anyway, thanks again for spotting this / testing.

anytime.  (while I can, 'povr' permitting.  ;-))


regards, jr.


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