POV-Ray : Newsgroups : povray.advanced-users : Isosurface to mesh Server Time: 20 Jun 2019 07:38:23 GMT
  Isosurface to mesh (Message 1 to 7 of 7)  
From: Mike Horvath
Subject: Isosurface to mesh
Date: 25 Nov 2016 06:43:00
Message: <5837dd74$1@news.povray.org>
Can anyone recommend the scripts on this site?

http://www.econym.demon.co.uk/isotut/approx.htm

I am currently rendering an image of my LCH color solid isosurface, and 
it is at 11% after 2.2 hours. And so far only the easiest parts.

Do you think I could benefit from converting to a mesh instead? Or is 
the benefit only if you want to render the scene multiple times (such as 
an animation)?

Thanks.


Mike


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From: Mike Horvath
Subject: Re: Isosurface to mesh
Date: 25 Nov 2016 08:14:54
Message: <5837f2fe$1@news.povray.org>
On 11/25/2016 1:43 AM, Mike Horvath wrote:
> Can anyone recommend the scripts on this site?
>
> http://www.econym.demon.co.uk/isotut/approx.htm
>
> I am currently rendering an image of my LCH color solid isosurface, and
> it is at 11% after 2.2 hours. And so far only the easiest parts.
>
> Do you think I could benefit from converting to a mesh instead? Or is
> the benefit only if you want to render the scene multiple times (such as
> an animation)?
>
> Thanks.
>
>
> Mike

I tried it and it's a bad choice I think. Edges aren't sufficiently 
sharp and smooth.

Mike


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From: Stephen
Subject: Re: Isosurface to mesh
Date: 25 Nov 2016 08:16:53
Message: <5837f375$1@news.povray.org>
On 11/25/2016 6:43 AM, Mike Horvath wrote:
> Can anyone recommend the scripts on this site?
>
> http://www.econym.demon.co.uk/isotut/approx.htm
>

Yes Mike's page is a treasure trove of hints and examples.
Thomas used Mike's Cityscape in our image "Dhalgren".
I have not used the isosurface approximation macro but I notice that 
there are two files adapted by Jaap Frank. I have a couple of macros 
written by Jaap and they work very well.

> I am currently rendering an image of my LCH color solid isosurface, and
> it is at 11% after 2.2 hours. And so far only the easiest parts.
>

Oh! Joy. :)

> Do you think I could benefit from converting to a mesh instead? Or is
> the benefit only if you want to render the scene multiple times (such as
> an animation)?
>

But you might want to render it many times as you adjust things like 
your texture or camera view. Just a thought.
Looking at your image in p.b.i. it is quite regular. I would try the 
approximation macro.

-- 

Regards
     Stephen


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From: Stephen
Subject: Re: Isosurface to mesh
Date: 25 Nov 2016 08:31:03
Message: <5837f6c7$1@news.povray.org>
On 11/25/2016 8:15 AM, Mike Horvath wrote:
> On 11/25/2016 1:43 AM, Mike Horvath wrote:
>> Can anyone recommend the scripts on this site?
>>
>> http://www.econym.demon.co.uk/isotut/approx.htm
>>
>> I am currently rendering an image of my LCH color solid isosurface, and
>> it is at 11% after 2.2 hours. And so far only the easiest parts.
>>
>> Do you think I could benefit from converting to a mesh instead? Or is
>> the benefit only if you want to render the scene multiple times (such as
>> an animation)?
>>
>> Thanks.
>>
>>
>> Mike
>
> I tried it and it's a bad choice I think. Edges aren't sufficiently
> sharp and smooth.
>

Did you use the version with subdivision and variable depth?
And you can always edit it to give sharp edges. In fact I would edit it 
anyway to make some faces flat and the curved face smooth.


-- 

Regards
     Stephen


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From: Mike Horvath
Subject: Re: Isosurface to mesh
Date: 25 Nov 2016 09:12:17
Message: <58380071@news.povray.org>
On 11/25/2016 3:30 AM, Stephen wrote:
> On 11/25/2016 8:15 AM, Mike Horvath wrote:
>> On 11/25/2016 1:43 AM, Mike Horvath wrote:
>>> Can anyone recommend the scripts on this site?
>>>
>>> http://www.econym.demon.co.uk/isotut/approx.htm
>>>
>>> I am currently rendering an image of my LCH color solid isosurface, and
>>> it is at 11% after 2.2 hours. And so far only the easiest parts.
>>>
>>> Do you think I could benefit from converting to a mesh instead? Or is
>>> the benefit only if you want to render the scene multiple times (such as
>>> an animation)?
>>>
>>> Thanks.
>>>
>>>
>>> Mike
>>
>> I tried it and it's a bad choice I think. Edges aren't sufficiently
>> sharp and smooth.
>>
>
> Did you use the version with subdivision and variable depth?
> And you can always edit it to give sharp edges. In fact I would edit it
> anyway to make some faces flat and the curved face smooth.
>
>


Yes, I tried with subdivision and the following values:

	#declare isoSegs = <32,32,32>;
	#declare Depth = 3;

The edges are still too rough. I've attached the result. I'm not good 
with modifying meshes by hand, so I will forego doing that. I will 
instead wait for the true isosurface to finish rendering.

There's one thing I'm worried about though. The place where the 
isosurface meets the cylinder showed holes or gaps last time I rendered 
a test image. But hopefully decreasing "accuracy" will clear up the issue.

Mike


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Attachments:
Download 'cielch_color_solid_cylinder_isosurface_mesh.png' (181 KB)

Preview of image 'cielch_color_solid_cylinder_isosurface_mesh.png'
cielch_color_solid_cylinder_isosurface_mesh.png


 

From: Stephen
Subject: Re: Isosurface to mesh
Date: 25 Nov 2016 10:16:45
Message: <58380f8d$1@news.povray.org>
On 11/25/2016 9:12 AM, Mike Horvath wrote:
> On 11/25/2016 3:30 AM, Stephen wrote:

>>
>> Did you use the version with subdivision and variable depth?
>> And you can always edit it to give sharp edges. In fact I would edit it
>> anyway to make some faces flat and the curved face smooth.
>>
>>
>
>
> Yes, I tried with subdivision and the following values:
>
>      #declare isoSegs = <32,32,32>;
>      #declare Depth = 3;
>
> The edges are still too rough. I've attached the result. I'm not good
> with modifying meshes by hand, so I will forego doing that. I will
> instead wait for the true isosurface to finish rendering.
>

Yes, that is rough and I wouldn't want to clean it up, myself.

> There's one thing I'm worried about though. The place where the
> isosurface meets the cylinder showed holes or gaps last time I rendered
> a test image. But hopefully decreasing "accuracy" will clear up the issue.
>

I have had to abandon several projects because the future did not arrive 
fast enough and my machine was vastly underpowered for what I wanted to 
do. :(



-- 

Regards
     Stephen


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From: Alain
Subject: Re: Isosurface to mesh
Date: 26 Nov 2016 23:20:09
Message: <583a18a9@news.povray.org>
Le 16-11-25 à 04:12, Mike Horvath a écrit :
> On 11/25/2016 3:30 AM, Stephen wrote:
>> On 11/25/2016 8:15 AM, Mike Horvath wrote:
>>> On 11/25/2016 1:43 AM, Mike Horvath wrote:
>>>> Can anyone recommend the scripts on this site?
>>>>
>>>> http://www.econym.demon.co.uk/isotut/approx.htm
>>>>
>>>> I am currently rendering an image of my LCH color solid isosurface, and
>>>> it is at 11% after 2.2 hours. And so far only the easiest parts.
>>>>
>>>> Do you think I could benefit from converting to a mesh instead? Or is
>>>> the benefit only if you want to render the scene multiple times
>>>> (such as
>>>> an animation)?
>>>>
>>>> Thanks.
>>>>
>>>>
>>>> Mike
>>>
>>> I tried it and it's a bad choice I think. Edges aren't sufficiently
>>> sharp and smooth.
>>>
>>
>> Did you use the version with subdivision and variable depth?
>> And you can always edit it to give sharp edges. In fact I would edit it
>> anyway to make some faces flat and the curved face smooth.
>>
>>
>
>
> Yes, I tried with subdivision and the following values:
>
>     #declare isoSegs = <32,32,32>;
>     #declare Depth = 3;
>
> The edges are still too rough. I've attached the result. I'm not good
> with modifying meshes by hand, so I will forego doing that. I will
> instead wait for the true isosurface to finish rendering.
>
> There's one thing I'm worried about though. The place where the
> isosurface meets the cylinder showed holes or gaps last time I rendered
> a test image. But hopefully decreasing "accuracy" will clear up the issue.
>
> Mike

It's a accuracy isue, but not the one you think of. It's a isue of 
floating point accuracy, or FPU accuracy.
In this case, try increasing the overall scale of your scene by 10: Put 
every objects and light_source into an union and add scale 10, then 
apply the same to the camera by multiplying the location and look_at 
also by 10.


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