POV-Ray : Newsgroups : povray.general : Do you rememb CGSphere ? Server Time
3 Mar 2024 17:38:51 EST (-0500)
  Do you rememb CGSphere ? (Message 1 to 9 of 9)  
From: kurtz le pirate
Subject: Do you rememb CGSphere ?
Date: 26 Jan 2024 12:17:22
Message: <65b3e922$1@news.povray.org>
Bonjour,


Too bad this project is dead. The site doesn't even exist anymore.

Anyway, I used the framework for an image on my site
<http://louisbel.free.fr/scenes/scene030.shtml> (sorry for the publicity
for my site ;) )


As you can see, some of the horizontal grid lines disappear depending on
the image size. It's a basic texture

#declare GroundTexture2 = texture {
 uv_mapping
 pigment { image_map { png "grid" map_type 0 once interpolate 2 } }
 finish { ambient 1 diffuse 0.6}
 }

Any idea how to avoid this problem ?
Thanks

-- 
Kurtz le pirate
Compagnie de la Banquise


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From: Bald Eagle
Subject: Re: Do you rememb CGSphere ?
Date: 26 Jan 2024 16:30:00
Message: <web.65b42344f2967d5e1f9dae3025979125@news.povray.org>
kurtz le pirate <kur### [at] gmailcom> wrote:

> As you can see, some of the horizontal grid lines disappear depending on
> the image size. It's a basic texture
>
> #declare GroundTexture2 = texture {
>  uv_mapping
>  pigment { image_map { png "grid" map_type 0 once interpolate 2 } }
>  finish { ambient 1 diffuse 0.6}
>  }
>
> Any idea how to avoid this problem ?
> Thanks

Looks to me like your lines are becoming less than one pixel high in those
areas, and so they get disappeared by antialiasing.

I would probably try to use a procedural texture, and then you can control the
thickness of the lines.
I have code somewhere that will calculate how wide an object needs to be to
remain above 1/2 pixel (just barely visible) or 1 pixel (solid) based upon
object distance from the camera, as well as camera and resolution settings.
You could also try some of those ... am+ whatever 0.01 method 3 ... things that
TdG and others have a much better handle on.   Much higher antialiasing settings
would help.

You also might find this interesting:

http://news.povray.org/povray.pov4.discussion.general/message/%3Cweb.65a0127673b7b02a1f9dae3025979125%40news.povray.org
%3E/#%3Cweb.65a0127673b7b02a1f9dae3025979125%40news.povray.org%3E


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From: William F Pokorny
Subject: Re: Do you rememb CGSphere ?
Date: 26 Jan 2024 16:55:16
Message: <65b42a44$1@news.povray.org>
On 1/26/24 12:17, kurtz le pirate wrote:
> Any idea how to avoid this problem ?

In the end you have to shoot enough rays to 'see' the grid lines for 
them to show up in the resulting image. For the grid lines to always 
look good / consistent you might have to shoot enough rays that for each 
pixel a significant percentage of the pixel's rays see the grid lines.

In official releases of POV-Ray, you can set an AA threshold value of 
0.0 and a sampling depth such that at smaller image sizes you 
effectively shoot as many rays as you would rendering a larger image.

Bill P.


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From: Thomas de Groot
Subject: Re: Do you rememb CGSphere ?
Date: 27 Jan 2024 02:26:11
Message: <65b4b013$1@news.povray.org>
Op 26/01/2024 om 18:17 schreef kurtz le pirate:
> 
> Bonjour,
> 
> 
> Too bad this project is dead. The site doesn't even exist anymore.
> 
> Anyway, I used the framework for an image on my site
> <http://louisbel.free.fr/scenes/scene030.shtml> (sorry for the publicity
> for my site ;) )
> 
> 
> As you can see, some of the horizontal grid lines disappear depending on
> the image size. It's a basic texture
> 
> #declare GroundTexture2 = texture {
>   uv_mapping
>   pigment { image_map { png "grid" map_type 0 once interpolate 2 } }
>   finish { ambient 1 diffuse 0.6}
>   }
> 
> Any idea how to avoid this problem ?
> Thanks
> 

What (always) helps for me in such cases is using stochastic 
antialiasing (+am3 etc) in the radiosity block (v3.7 & v3.8):

//+w1000 +h450 +am3 +a0.01 +ac0.90 +r3 +bm2 +bs8 +wt7

#declare Stochastic = on;

and in the radiosity { } block adapt count:
     #if (Stochastic)
       count 10
     #else
       count 50, 1000
     #end

if I am not wrong, 'stochastic' is explained in the wiki documentation.

-- 
Thomas


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From: Bald Eagle
Subject: Re: Do you rememb CGSphere ?
Date: 27 Jan 2024 08:35:00
Message: <web.65b50569f2967d5e1f9dae3025979125@news.povray.org>
kurtz le pirate <kur### [at] gmailcom> wrote:
> Bonjour,
>
>
> Too bad this project is dead. The site doesn't even exist anymore.

Yes, it's not even archived on the WayBack machine.
But there are a bunch of renders saved to other platforms like Pinterest.

And look what I found.   :)


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From: kurtz le pirate
Subject: Re: Do you rememb CGSphere ?
Date: 27 Jan 2024 08:43:24
Message: <65b5087c@news.povray.org>
On 27/01/2024 08:26, Thomas de Groot wrote:

> 
> What (always) helps for me in such cases is using stochastic 
> antialiasing (+am3 etc) in the radiosity block (v3.7 & v3.8):
> 
> //+w1000 +h450 +am3 +a0.01 +ac0.90 +r3 +bm2 +bs8 +wt7
> 



Yes, stochastic antialiasing (with Thresold = 0) work do the trick !!

But rendering time has increased considerably :

Method 1, Threshold 0.300, Depth 3, Jitter 1.00, Gamma 2.50 :
*1 minutes 51 seconds*

Method 3, Threshold 0.000, Depth 3, Jitter 1.00, Gamma 2.50 :
*48 minutes 19 seconds*

That is twenty-six times longer. As long as the image is good ;)
I update my web page.




@Bald Eagle : yes, Inigo Quilez web site is the site is really very
interesting but I have some trouble understanding a lot of things.



Thanks.

-- 
Kurtz le pirate
Compagnie de la Banquise


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From: Bald Eagle
Subject: Re: Do you rememb CGSphere ?
Date: 27 Jan 2024 10:10:00
Message: <web.65b51c5af2967d5e1f9dae3025979125@news.povray.org>
kurtz le pirate <kur### [at] gmailcom> wrote:

> @Bald Eagle : yes, Inigo Quilez web site is the site is really very
> interesting but I have some trouble understanding a lot of things.

You and me, both, my friend.  It's a whole different way of thinking.





But therein lies the power.






- BE


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From: Cousin Ricky
Subject: Re: Do you rememb CGSphere ?
Date: 27 Jan 2024 15:25:34
Message: <65b566be$1@news.povray.org>
On 2024-01-26 13:17 (-4), kurtz le pirate wrote:
> 
> Too bad this project is dead. The site doesn't even exist anymore.

There is an active CGSphere group in the Zuckisphere:

  https://www.facebook.com/groups/194474654695

Some of us have reposted our spheres there.

I still have the include files for creating CGSpheres with POV-Ray, and
I have made some modifications to suit my needs.  Unfortunately, I do
not know the intellectual property rights status of these files;
otherwise, I'd post them.  If I'm not mistaken, Trevor G. Quayle made
the adaptation for POV-Ray, but I haven't seen him around lately.

> As you can see, some of the horizontal grid lines disappear depending on
> the image size. It's a basic texture
> 
> [snip]
> 
> Any idea how to avoid this problem ?

In addition to stochastic anti-aliasing (+AM3) or zero threshold
(+A0.0), which were mentioned by others, two more solutions are depth of
field (which is also stochastic), and rendering at a large size and then
downsizing the image.  2400 x 2400, which is 3 times the "official"
size, is sufficient to catch all the lines with the setup I downloaded
long ago.


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From: kurtz le pirate
Subject: Re: Do you rememb CGSphere ?
Date: 29 Jan 2024 06:05:08
Message: <65b78664@news.povray.org>
On 26/01/2024 22:25, Bald Eagle wrote:
> I would probably try to use a procedural texture, and then you can control the
> thickness of the lines.

The stochastic method is definitely the best method !

Here, two images : one with "original" antialiasing, one with am3/0.0.
And yes, the grid plane is procedural.


In all the time I've been using POV, I've never used this superb option.
I'm ashamed :(






-- 
Kurtz le pirate
Compagnie de la Banquise


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