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22 May 2024 23:43:35 EDT (-0400)
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From: Ilya Razmanov
Subject: Height field to mesh - more resolution
Date: 29 Nov 2023 23:59:05
Message: <65681699$1@news.povray.org>
Greeting,

continuing experiments with Python (which continues to piss me off), I 
decided to write small program to convert image heightfields into 
triangle meshes. My may intention was to improve quality for 
heightfields having both small image size and low bit depth - I supposed 
that converting them into meshes will make POVRay interpolate 
nonexisting data, thus improving visual appearance.

Attached is my test image 1.test grey 001.png, used as a heightfield 
(with "smooth" on) for rendering 2.heightfield.jpg. Since the source is 
only 64 * 64 pixels, result looks... well, correspondingly.

Next, I created my converter (attached as img2mesh.01.004.py.bz2) and 
used it to convert the same source into triangle mesh. Rendering result 
is attached as 3.img2mesh.01.004.jpg and, as you can see, it's clearer 
but full of holes. After that I finally took a look at POVRay docs, that 
say that POVRay internally uses 4 pixels for 2 triangles, just like my 
program (never read docs before doing something yourself - it's 
discouraging!), except for I didn't do force connection of square 
corners, that lead to a holes. Instead of fixing it (I find fixing 
discouraging too), I simply invented different approach - using 4 pixels 
for 4 triangles (don't tell me if this is described somewhere already), 
that lead to a completely different program, attached as 
img2mesh.02.001.py.bz2), which provides output like attached 
4.img2mesh.02.001.jpg.

The latter looks to me significantly better than POVRay heightfield 
rendering (not to mention my first attempt), although I plan some 
additional explorations (artifacts on flat surfaces are still 
unexplained, and I even start to suspect POVRay roundoff errors).

Meanwhile, I hope someone will find this tiny utility useful, and 
probably even come with new ideas.

Prerequisites:

1) Python (I used 3.12 but previous versions of Python 3 are supposed to 
be fine). Seem to be preinstalled on many computers nowadays (that's how 
I got it, for example). My program is equipped with minimal GUI, using 
tkinter, which seem to be redistributed with all standard Python 
distributions, so doesn't require separate download.
2) Pillow for reading images. As a simple image reading library, pillow 
is distributed everywhere; at worst, it takes few seconds to download 
and no seconds to install and configure.

So, have a day.

Ilya


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Attachments:
Download '1.test grey 001.png' (2 KB) Download '2.heightfield.jpg' (9 KB) Download 'img2mesh.01.004.py.bz2.zip' (3 KB) Download '3.img2mesh.01.004.jpg' (14 KB) Download 'img2mesh.02.001.py.bz2.zip' (2 KB) Download '4.img2mesh.02.001.jpg' (10 KB)

Preview of image '1.test grey 001.png'
1.test grey 001.png

Preview of image '2.heightfield.jpg'
2.heightfield.jpg

Preview of image '3.img2mesh.01.004.jpg'
3.img2mesh.01.004.jpg

Preview of image '4.img2mesh.02.001.jpg'
4.img2mesh.02.001.jpg


 

From: jr
Subject: Re: Height field to mesh - more resolution
Date: 30 Nov 2023 09:00:00
Message: <web.656895462c1eda44f11225116cde94f1@news.povray.org>
hi,

Ilya Razmanov <ily### [at] gmailcom> wrote:
> Greeting,
>
> continuing experiments with Python (which continues to piss me off), I
> decided to write small program to convert image heightfields into
> triangle meshes. ...
> The latter looks to me significantly better than POVRay heightfield
> rendering ...

for data "extrapolated" from a 64x64 image, that last image looks real good I
think.  wondering if the calculation could not be done in SDL ?


regards, jr.


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From: Ilya Razmanov
Subject: Re: Height field to mesh - more resolution
Date: 30 Nov 2023 21:21:56
Message: <65694344$1@news.povray.org>
On 30.11.2023 16:59, jr wrote:

> for data "extrapolated" from a 64x64 image, that last image looks real good I
> think.  wondering if the calculation could not be done in SDL ?

For this to be done within POVRay only, I need:
1) POVRay opening image as some sort of array with easy access to any 
pixel data I want
2) Not only math but some programming (I need cycles first of all)

What as to 1), surely, POVRay have something to read images - after all, 
it uses images as heightfield, that requires image reading and 
representation as some data structure internally. But I see no way for 
*me* to access these data directly. Well, after all, POVRay is neither a 
bitmap editor, nor a programming environment (or, as our CC said, 
"neither both"). So, I use external tool, taking advantage of that POV 
language is simple text, easy to understand and write. I used Python 
since I got my Windows notebook with Python 3.8 preinstalled, and I was 
curious enough to take a look at what is this and what it is good for. 
As long as I know, it also comes preinstalled with Linux, and, in 
general, looks to be more widely available than POVRay itself, that 
makes my tiny programs cross-platform. And, since POV files are so easy 
to write, why not to use this advantage of POVRay? ;-)

Ilya


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From: jr
Subject: Re: Height field to mesh - more resolution
Date: 30 Nov 2023 23:55:00
Message: <web.656965f42c1eda44f11225116cde94f1@news.povray.org>
hi,

Ilya Razmanov <ily### [at] gmailcom> wrote:
> > for data "extrapolated" from a 64x64 image, that last image looks real good I
> > think.  wondering if the calculation could not be done in SDL ?
> For this to be done within POVRay only, I need:
> 1) POVRay opening image as some sort of array with easy access to any
> pixel data I want
> 2) Not only math but some programming (I need cycles first of all)

aiui, POV-Ray (as of 3.7) has the "tools", and your first script (the spheres
image) would, I think, be fairly straightforward to code up in SDL.  hence my
question re the details of the height_field processing.


> ...
> As long as I know, it also comes preinstalled with Linux, and, in
> general, looks to be more widely available than POVRay itself, that
> makes my tiny programs cross-platform. And, since POV files are so easy
> to write, why not to use this advantage of POVRay? ;-)

:-)  I'm sure many/most (can) use Python, but all of us have POV-Ray to use.


regards, jr.


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From: ingo
Subject: Re: Height field to mesh - more resolution
Date: 1 Dec 2023 01:50:00
Message: <web.656981f02c1eda4417bac71e8ffb8ce3@news.povray.org>
Ilya Razmanov <ily### [at] gmailcom> wrote:
> On 30.11.2023 16:59, jr wrote:
>
> > for data "extrapolated" from a 64x64 image, that last image looks real good I
> > think.  wondering if the calculation could not be done in SDL ?
>
> For this to be done within POVRay only, I need:
> 1) POVRay opening image as some sort of array with easy access to any
> pixel data I want
> 2) Not only math but some programming (I need cycles first of all)

you can use an image as a pattern and you can use a pattern in a function. Then
you can sample the "image function" to fill arrays. But, the image will already
be interpolated.

ingo


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From: jr
Subject: Re: Height field to mesh - more resolution
Date: 1 Dec 2023 02:05:00
Message: <web.6569853a2c1eda44f11225116cde94f1@news.povray.org>
"jr" <cre### [at] gmailcom> wrote:
> Ilya Razmanov <ily### [at] gmailcom> wrote:
> ...> > For this to be done within POVRay only, I need:
> aiui, POV-Ray (as of 3.7) has the "tools", ...

proof of concept (640x480 image source).  ~20 minutes ;-)


regards, jr.

-----<snip>-----
/* cf Iyla's "spheres" script */

#version 3.8;

#include "functions.inc"

global_settings {assumed_gamma 1}

#declare im_ = pigment {
  image_map {
    png "s_o_l.png"
    gamma 1
  }
  scale <640,480,1>
};

#declare ext_ = max_extent(im_);

#declare arr_ = array [640][480];

#for (r_,0,479)
  #for (c_,0,639)
    #local arr_[c_][r_] = eval_pigment(im_,<c_,r_,.5>);
  #end
#end

#for (r_,0,479)
  #for (c_,0,639)
    sphere {
      <(c_+.5),(r_+.5),0>, .495
      texture {
        pigment {arr_[c_][r_]}
        finish {emission 1}
      }
    }
  #end
#end

camera {
  location <320,240,-275>
  right x * (4/3)
  up y
  angle 90
  look_at <320,240,0>
}


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Attachments:
Download '231201_ir.png' (960 KB)

Preview of image '231201_ir.png'
231201_ir.png


 

From: Thomas de Groot
Subject: Re: Height field to mesh - more resolution
Date: 1 Dec 2023 03:15:41
Message: <6569962d$1@news.povray.org>
Op 1-12-2023 om 08:03 schreef jr:
> "jr" <cre### [at] gmailcom> wrote:
>> Ilya Razmanov <ily### [at] gmailcom> wrote:
>> ...> > For this to be done within POVRay only, I need:
>> aiui, POV-Ray (as of 3.7) has the "tools", ...
> 
> proof of concept (640x480 image source).  ~20 minutes ;-)
> 

LOL!

-- 
Thomas


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From: William F Pokorny
Subject: Re: Height field to mesh - more resolution
Date: 1 Dec 2023 09:13:40
Message: <6569ea14$1@news.povray.org>
On 12/1/23 02:03, jr wrote:
> proof of concept (640x480 image source).  ~20 minutes 😉

This a good example to show the value of the yuqk / v4.0 idea of 
providing a 'munctions.inc' / macro defined functions include.

The yuqk fork has no 'eval_pigment', but it does have a munction called 
   M_evaluate_pigment(). The following runs in about 4.5 seconds, 
elapsed, on my old i3.

In this case, I think, you can mostly emulate what was done with 
M_evaluate_pigment() in official releases of POV-Ray - to some degree or 
other.

Bill P.

----- snip ------
#version unofficial 3.8; // yuqk
#if (file_exists("version.inc"))
     #include "version.inc"
#end
#if (!defined(Fork_yuqk))
     #error "This POV-Ray SDL code requires the yuqk fork."
#end
global_settings { assumed_gamma 1 }
#declare Grey50 = srgb <0.5,0.5,0.5>;
background { Grey50 }
#declare VarOrthoMult =
     2.0/max(image_width/image_height,image_height/image_width);
#declare Camera01z = camera {
     orthographic
     location <0,0,-2>
     direction z
     right VarOrthoMult*x*max(1,image_width/image_height)
     up VarOrthoMult*y*max(1,image_height/image_width)
}
#declare PigIm = pigment {
     image_map {
         png "Test680x480.png"
         gamma srgb
         interpolate 0
     }
     scale <640,480,1>
};
#include "munctions.inc"
// Following defines FnPg00() so it can be used directly.
#declare Vec00 =
M_evaluate_pigment("FnPg00",PigIm,<0,0,0>,false);

//--- scene ---
union {
#for (R,0,479)
     #for (C,0,639)
         sphere {
           <(C+.5),(R+.5),0>, .495
           texture {
             pigment {
                 // Can call 'munction' repeatedly too, but it's
                 // 2x slower than FnPg00() due the macro call.
               //color
               //M_evaluate_pigment("FnPg00",PigIm,<C,R,0>,false)
                 color FnPg00(C,R,0)
             }
             finish {emission 1}
           }
         }
     #end
#end
scale <1/640,1/480,1>
translate <-0.5,-0.5,0>
scale <VarOrthoMult*max(1,image_width/image_height),
     VarOrthoMult*max(1,image_height/image_width),
     1>
}
camera { Camera01z }
----- snip ------


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Attachments:
Download 'jr.png' (33 KB)

Preview of image 'jr.png'
jr.png


 

From: William F Pokorny
Subject: Re: Height field to mesh - more resolution
Date: 1 Dec 2023 10:10:46
Message: <6569f776$1@news.povray.org>
On 12/1/23 09:13, William F Pokorny wrote:
> This a good example

Apologies for attaching the pointless image. Foggy mind / autopilot :-(

Bill P.


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From: jr
Subject: Re: Height field to mesh - more resolution
Date: 1 Dec 2023 11:25:00
Message: <web.656a07e52c1eda44f11225116cde94f1@news.povray.org>
hi,

William F Pokorny <ano### [at] anonymousorg> wrote:
> On 12/1/23 02:03, jr wrote:
> > proof of concept (640x480 image source).  ~20 minutes 😉
> ...
> The yuqk fork has no 'eval_pigment', but it does have a munction called
>    M_evaluate_pigment(). The following runs in about 4.5 seconds,
> elapsed, on my old i3.

that's pretty good.  modifying my posted code to junk the array and call
'eval_pigment' inside the 'texture{}', I get parsing down to just under 5.5 secs
(plus ~1s render) using the beta.2.

have not tried tried to install the renamed branch yet, will try later tonight
to get your code to run with last-but-one-before-renaming version.


> Apologies for attaching the pointless image. Foggy mind / autopilot :-(

:-)


@Ilya

sorry about misspelling your name in the posted scene code, have corrected my
local copy.


regards, jr.


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