POV-Ray: Newsgroups: povray.binaries.images: Blob: problem or no problem?: Re: Blob: problem or no problem?

POV-Ray : Newsgroups : povray.binaries.images : Blob: problem or no problem? : Re: Blob: problem or no problem?		Server Time 7 Nov 2024 13:39:54 EST (-0500)

From: Le Forgeron
Date: 19 Jul 2015 06:30:46
Message: <55ab7c56@news.povray.org>

Le 18/07/2015 22:19, LanuHum a écrit :
> Cousin Ricky <ric### [at] yahoocom> wrote:
>> On 2015-07-18 04:30 AM (-4), LanuHum wrote:
>>> Picture shows results of Blender Internal Render and POV-Ray.
>>> I can achieve smoothing as in Internal or not?
>>
>>
>> Does Blender use a different blob formula?  I wrote my own blob formul
a,
>> to be implemented as an isosurface, which often gives smoother results

>> than POV-Ray's native blob, showing that the formula makes a differenc
e.
>>
> 
> Thanks!
> I will hope that clipka and Le Forgeron will see it.
> :)

Hi :-)

understanding blob can be complex.

> http://www.shipbrook.net/jeff/raytrace/blobs.html

b1.png is your original povray version

b2.png is the same, with visualisation of the influence of the components
.

Notice how the mark/shadow is at the boundary of the influence. That is
normal, (double that! It's due to the computation of the normal) and if
you want to get ride of it, you need to adjust the components.

The page above gives the formula to know the radius on the picture:

a = sqrt(1-sqrt(0.8/2))*1.702 = 1.0319

The distance between the blob is 3.678887, so the unscaled component, to
not influence each normal, should have a radius of less than 2.0726/2,
that is 1.0363

With a radius of 1.0363 and an apparent radius of 1.0319, the strength
(same page for formula) is going to be

s = 10816.6446 (or even 11141.445983 with more precision)

That's a bit strong to have a smooth transition when connecting the two
spheres with a cylinder. (b3.png and b4.png)

The spheres do not need to not intersect, the intersection must just be
not visible. So we can reduce the strengh with a bigger radius (yet
smaller than the initial radius).

A radius of 1.4 need a more reasonable strength of 3.83512 , yet it's
still too much (b5.png , with a cylinder in b6.png)

A radius of 1.2 has a strength of 11.7850 , some of which can be used in
a cylinder of 1.2 radius connecting the two spheres (b7.png, b8.png and
b805.png)

#declare Ssph = 10.7850 - clock;
#declare Scyl = 1+clock;

#declare data_Mball_ob = blob {
    threshold 0.8
    sphere { <0,0,0>, 1.2, Ssph texture {Default_texture} scale
<1.775,1.775,1.775> translate <-0.919648, 0.000000, 0.000000>}
    sphere { <0,0,0>, 1.2, Ssph texture {Default_texture} scale
<1.775,1.775,1.775> rotate <-2.504e-06,-0,0> translate <-4.598535, 0.0000
00,
0.000000>}
    cylinder { <-0.5181, 0.000000, 0.000000>, <-2.5907,0,0>, 1.2, Scyl
texture {Default_texture} scale <1.775,1.775,1.775> }
}

Playing with a weaker strength is the way to a smaller transition, this
can be done with adjusting the radius (bigger than 1.2) and recomputing
the total strength to share between the spheres and the cylinder.