POV-Ray : Newsgroups : povray.binaries.images : Isosurface intersection artifacts Server Time: 27 Mar 2017 02:47:46 GMT
  Isosurface intersection artifacts (Message 1 to 8 of 8)  
From: Mike Horvath
Subject: Isosurface intersection artifacts
Date: 25 Nov 2016 16:51:06
Message: <58386bfa$1@news.povray.org>
You can see in the image there is a jagged line where the isosurface 
intersects the cylinder. Is it possible to get rid of this completely?

I have set accuracy very low to 0.0001 and max gradient very high to 
10000, but I'm afraid it will never go away completely.

Thanks.


Mike


Post a reply to this message


Attachments:
Download 'cielch_color_solid_cylinder_isosurface_backup_05.png' (24 KB)

Preview of image 'cielch_color_solid_cylinder_isosurface_backup_05.png'
cielch_color_solid_cylinder_isosurface_backup_05.png


 

From: clipka
Subject: Re: Isosurface intersection artifacts
Date: 25 Nov 2016 17:03:13
Message: <58386ed1$1@news.povray.org>
Am 25.11.2016 um 17:51 schrieb Mike Horvath:
> You can see in the image there is a jagged line where the isosurface
> intersects the cylinder. Is it possible to get rid of this completely?
> 
> I have set accuracy very low to 0.0001 and max gradient very high to
> 10000, but I'm afraid it will never go away completely.

You might try changing the overall scale of the entire scene.

An overly high max_gradient will not help at all, and will only increase
render time.


Post a reply to this message

From: Cousin Ricky
Subject: Re: Isosurface intersection artifacts
Date: 26 Nov 2016 03:00:00
Message: <web.5838f9774532f3c8e8ae267f0@news.povray.org>
Mike Horvath <mik### [at] gmailcom> wrote:
> You can see in the image there is a jagged line where the isosurface
> intersects the cylinder. Is it possible to get rid of this completely?
>
> I have set accuracy very low to 0.0001 and max gradient very high to
> 10000, but I'm afraid it will never go away completely.

This is probably the same problem I had in this thread:

http://news.povray.org/povray.binaries.images/thread/%3Cweb.48cd3df6832f1b9885de7b680%40news.povray.org%3E/


Post a reply to this message

From: Mike Horvath
Subject: Re: Isosurface intersection artifacts
Date: 26 Nov 2016 12:54:26
Message: <58398602$1@news.povray.org>
On 11/25/2016 9:54 PM, Cousin Ricky wrote:
> Mike Horvath <mik### [at] gmailcom> wrote:
>> You can see in the image there is a jagged line where the isosurface
>> intersects the cylinder. Is it possible to get rid of this completely?
>>
>> I have set accuracy very low to 0.0001 and max gradient very high to
>> 10000, but I'm afraid it will never go away completely.
>
> This is probably the same problem I had in this thread:
>
>
http://news.povray.org/povray.binaries.images/thread/%3Cweb.48cd3df6832f1b9885de7b680%40news.povray.org%3E/
>
>

Excellent! That did the trick I think.

Mike


Post a reply to this message

From: INVALID ADDRESS
Subject: Re: Isosurface intersection artifacts
Date: 26 Nov 2016 18:12:18
Message: <787526097.501876608.045297.gdsHYPHENentropyAThotmaolDOTcom@news.povray.org>
clipka <ano### [at] anonymousorg> wrote:
> Am 25.11.2016 um 17:51 schrieb Mike Horvath:
>> You can see in the image there is a jagged line where the isosurface
>> intersects the cylinder. Is it possible to get rid of this completely?
>> 
>> I have set accuracy very low to 0.0001 and max gradient very high to
>> 10000, but I'm afraid it will never go away completely.
> 
> You might try changing the overall scale of the entire scene.
> 
> An overly high max_gradient will not help at all, and will only increase
> render time.
> 
> 

Out of curiosity, how close to "as good as it gets" is isosurface
performance? I love the things but they are prohibitively slow most of the
time...at least for the things I do with them, which is probably all sorts
of backwards and wrong to begin with. :)

Ian


Post a reply to this message

From: clipka
Subject: Re: Isosurface intersection artifacts
Date: 26 Nov 2016 19:28:52
Message: <5839e274$1@news.povray.org>
Am 26.11.2016 um 19:12 schrieb [GDS|Entropy]:
> clipka <ano### [at] anonymousorg> wrote:
>> Am 25.11.2016 um 17:51 schrieb Mike Horvath:
>>> You can see in the image there is a jagged line where the isosurface
>>> intersects the cylinder. Is it possible to get rid of this completely?
>>>
>>> I have set accuracy very low to 0.0001 and max gradient very high to
>>> 10000, but I'm afraid it will never go away completely.
>>
>> You might try changing the overall scale of the entire scene.
>>
>> An overly high max_gradient will not help at all, and will only increase
>> render time.
>>
>>
> 
> Out of curiosity, how close to "as good as it gets" is isosurface
> performance? I love the things but they are prohibitively slow most of the
> time...at least for the things I do with them, which is probably all sorts
> of backwards and wrong to begin with. :)

There are certainly still ways to optimize, at least for special cases.

One such example would be functions whith lots of subexpressions, each
of which affect the result only in a well-defined region of space, like
the components in a blob.

Other approaches would involve preprocessing the isosurface prior to
rendering -- whether it is conversion to a mesh, pre-computing of
samples in a spatial tree (with the extreme being conversion to voxel
data), or other such fancy stuff.

And last not least there's the execution speed of the user-defined
functions. At present they are executed by a homegrown virtual machine,
which is quite simple and therefore presumably quite fast, but most
certainly no match for just-in-time-compiled code.


Post a reply to this message

From: Alain
Subject: Re: Isosurface intersection artifacts
Date: 26 Nov 2016 22:51:26
Message: <583a11ee$1@news.povray.org>
Le 16-11-26 à 13:12, [GDS|Entropy] a écrit :
> clipka <ano### [at] anonymousorg> wrote:
>> Am 25.11.2016 um 17:51 schrieb Mike Horvath:
>>> You can see in the image there is a jagged line where the isosurface
>>> intersects the cylinder. Is it possible to get rid of this completely?
>>>
>>> I have set accuracy very low to 0.0001 and max gradient very high to
>>> 10000, but I'm afraid it will never go away completely.
>>
>> You might try changing the overall scale of the entire scene.
>>
>> An overly high max_gradient will not help at all, and will only increase
>> render time.
>>
>>
>
> Out of curiosity, how close to "as good as it gets" is isosurface
> performance? I love the things but they are prohibitively slow most of the
> time...at least for the things I do with them, which is probably all sorts
> of backwards and wrong to begin with. :)
>
> Ian
>

Set your max_gradient value as low as you can without degrading the object.
In some cases, using evaluate instead of max_gradient can improve your 
performance. I've seen cases where the improvement was prety good.
Using pow() instead of multipliyng a variable by itself can help, 
especialy in the case of a cube or higher power.
If your equation(s) can be writen in several ways, it's possible that 
some of those ways to be more effecient. Try it if possible.
Make the container as tight as possible. It reduce the sampling needed 
and often help in reducing the max_gradient.

In case of artefacts around areas where the isosurface intersect another 
surface, try increasing the overall scale of the scene. This also work 
with blobs.


Post a reply to this message

From: INVALID ADDRESS
Subject: Re: Isosurface intersection artifacts
Date: 27 Nov 2016 12:46:11
Message: <1368151571.501943393.962224.gdsHYPHENentropyAThotmaolDOTcom@news.povray.org>
Alain <kua### [at] videotronca> wrote: 
> Set your max_gradient value as low as you can without degrading the object.
> In some cases, using evaluate instead of max_gradient can improve your 
> performance. I've seen cases where the improvement was prety good.
> Using pow() instead of multipliyng a variable by itself can help, 
> especialy in the case of a cube or higher power.
> If your equation(s) can be writen in several ways, it's possible that 
> some of those ways to be more effecient. Try it if possible.
> Make the container as tight as possible. It reduce the sampling needed 
> and often help in reducing the max_gradient.
> 
> In case of artefacts around areas where the isosurface intersect another 
> surface, try increasing the overall scale of the scene. This also work 
> with blobs.
> 

Thanks man I will give that a shot! :)

Ian


Post a reply to this message

Copyright 2003-2008 Persistence of Vision Raytracer Pty. Ltd.