POV-Ray : Newsgroups : povray.binaries.images : 'solid media' human model : Re: 'solid media' human model Server Time
27 May 2022 23:22:31 EDT (-0400)
  Re: 'solid media' human model  
From: Kenneth
Date: 16 Apr 2022 10:05:00
Message: <web.625ac52bd1523eea4cef624e6e066e29@news.povray.org>
Thomas de Groot <tho### [at] degrootorg> wrote:

> Ah! One of my favourite pastimes too indeed, either with media (ghosts)
> or with objects. yours is an intriguing media.

Thanks. And I might have an interesting alternative to this media technique
(which is kind of off-topic):

Over the past several hours, I have come up with what looks to be a very simple
way to turn any pre-made object into an isosurface. No mathematical wizardry
involved, just using POV-ray's 'object pattern' (in a rather odd way) and
turning it into a function for shaping the isosurface.

I have attached my first test image. (No media involved here, BTW.) I don't want
to post the details yet, because there are some *very* strange quirks that I am
seeing-- not with the technique itself (I hope!), but with how the camera and
lights are interacting with the result.  For example, in this test scene the
final isosurface is centered on the origin, the camera is looking directly into
+ z, and there are two lights:

  color rgb .8*<.3,1,1> // BLUE-GREEN
  translate <20, 40, -20> // in +x


  color rgb .8*<1,.2,.2> // RED
  translate <-20, 40, -20> // in -x

These lights cover the model fairly well-- but the vertical 'dividing line'
between the lights' coverage makes no sense. That line is at x=0...but also
varies position as I move the camera. From testing this quirk, it appears that
the position of the lights (relative to that x=0 'vertical plane') causes each
light to illuminate only half of the isosurface(!)-- and on the opposite side.
There also seem to be some 'reversed shadows' on the model. I
have never seen such strange results before. (All of this might be due to the
odd way I had to use the object pattern and its two required colors, but I don't
yet know...)

BTW, this partial render took 27 minutes on my Core-I7 Windows machine (8
cores/16 threads)-- *much* slower than my 'solid media' examples. For the
isosurface, I had to use  accuracy 0.0001 and  max_gradient 20000 (!), and the
result still doesn't look very smooth.

In any case, this stuff is off-topic here, but I wanted to give a preliminary
hint that the general idea *might* work for converting pre-declared objects into
isosurfaces... which can then be further 'disturbed' by other functions. If I
can figure out the reason for the quirks and fix them, I will post the full
details elsewhere.

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Download 'object_converted_to_isosurface_test_1_kw.jpg' (33 KB)

Preview of image 'object_converted_to_isosurface_test_1_kw.jpg'


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