POV-Ray : Newsgroups : povray.general : Height field to mesh - more resolution : Height field to mesh - more resolution Server Time
20 May 2024 17:31:54 EDT (-0400)
  Height field to mesh - more resolution  
From: Ilya Razmanov
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


Post a reply to this message


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


 

Copyright 2003-2023 Persistence of Vision Raytracer Pty. Ltd.