POV-Ray : Newsgroups : povray.general : Mapping Textures on irregular shapes : Re: Mapping Textures on irregular shapes Server Time
15 Jul 2024 21:09:25 EDT (-0400)
  Re: Mapping Textures on irregular shapes  
From: Bald Eagle
Date: 22 Apr 2020 20:25:01
Message: <web.5ea0dffb72e01857fb0b41570@news.povray.org>
"Josh" <nomail@nomail> wrote:
> Thanks, this is helpful! If I have a shape in Wings3D for example and export it
> as an OBJ, will it automatically have a "uv_map"? Or do I have to 'create' one
> by hand?

I don't think it will automatically do it - but others may have more experience.

I have seen some videos about "unwrapping" shapes in other software packages
like Grasshopper, Blender, Maya, etc ---

The idea there, as far as I can tell, is that you start with a blank "skin" and
"peel" your shape, and then arrange that onto a rectangular uv mapping texture,
and so "physically" move the coordinates from the skin to the texture and create
the 1-to-1 mapping.  You wind up with something that looks like the pieces in a
fabric pattern for sewing.

Kinda like you might slice up a globe and try to flatten it to get a transverse
Mercator projection:

https://www.wolfram.com/mathematica/new-in-10/geographic-visualization/make-a-map-that-wraps-a-globe.html

Once you wrap your head around that (pun intended) you'll begin to appreciate
why it would be so hard to try and do this automatically, and _well_.


Depending on the effect you're going for, it may be best to try a procedural
texture with some surface-dependent texture modifiers like AOI, slope, slope or
normal maps (not like the one you used for the game engine), etc.


Now, maybe Jerome Grimbert might have a good idea about whether or not NURBS
allows you to model a shape from scratch AND get a uv-mapping function-of-sorts
as an incidental byproduct...

Maybe post a sample asteroid shape and a sample or link(s) to the kind of thing
you're shooting for?  Folks may have some practical ideas.


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