POV-Ray : Newsgroups : povray.general : Blob issue Server Time
17 Apr 2025 01:55:26 EDT (-0400)
  Blob issue (Message 1 to 2 of 2)  
From: Paul Bourke
Subject: Blob issue
Date: 18 Mar 2025 01:45:00
Message: <web.67d90848553f395c386dcd2784a083c@news.povray.org>
Another one ... please see zip archive here with scene and data file
   https://paulbourke.net/transient/povray2/
And sample render attached, PovRay 3.8.
What causing the black defects? Seem to only be on close parts of the blob.
Note PovRay 3.7 gives "There are more than the maximum supported components in a
blob."


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From: William F Pokorny
Subject: Re: Blob issue
Date: 18 Mar 2025 14:46:00
Message: <67d9bf68$1@news.povray.org>
On 3/18/25 01:44, Paul Bourke wrote:
> Another one ... please see zip archive here with scene and data file
>     https://paulbourke.net/transient/povray2/
> And sample render attached, PovRay 3.8.
> What causing the black defects? Seem to only be on close parts of the blob.
> Note PovRay 3.7 gives "There are more than the maximum supported components in a
> blob."
> 

I'd bet on numerical issues with the blob code or the solvers which are 
fixed(*) in the yuqk fork. No idea which fixes in particular.

In the attached image (no AA) the top sub image is the v3.8 beta 2 
result; The middle sub-image is the yuqk fork result; The bottom 
sub-image shows the differences.

I see black artefacts in the v3.8 result where there are differences 
shown in the bottom sub-image.

---

Aside 1 : We can, in the spherical camera, use angles like 360,360 as I 
did here for the images posted. And though the documentation implies 
limits, we can in fact use values >360 for both angles. Has anyone found 
a use for this somewhat hidden(**) capability?

I've had the thought maybe we could get to an ODS camera capability by 
adding two optional 2D offset vectors after the two spherical camera 
angles - which would be applied by multiples on mod(angle,360)s to get 
different eye pupil positions. Might have some work to get the pixels 
into a more standard positions for ODS viewing, but - maybe - we can get 
to some ODS support without adding more cameras.

Aside 2: Another thought with folks recently discussing ODS cameras with 
respect to your scene. The disc / polygon orienting would be slightly 
off for one or both eyes, if the ODS image is created via one scene and 
render. Perhaps not enough to matter?

Bill P.

(*) Cleaner. Floating point numerical limitations never really go away...

(**) - 'hidden' so I don't have to spell 'secret', Bill W.


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Attachments:
Download 'sceneloop0400_v38b2_to_sceneloop0400_yuqk.jpg' (167 KB)

Preview of image 'sceneloop0400_v38b2_to_sceneloop0400_yuqk.jpg'
sceneloop0400_v38b2_to_sceneloop0400_yuqk.jpg


 

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