POV-Ray : Newsgroups : povray.general : uv mapping triangles in mesh {} : Re: uv mapping triangles in mesh {} Server Time
3 Jun 2023 03:59:35 EDT (-0400)
  Re: uv mapping triangles in mesh {}  
From: Thomas de Groot
Date: 24 Mar 2023 05:21:02
Message: <641d6b7e$1@news.povray.org>
Op 24-3-2023 om 09:10 schreef Kenneth:
> Thomas de Groot <tho### [at] degrootorg> wrote:
>>
>> What you need is
>> making sure that your pattern object (i.e. the torus) interects your
>> primary object (i.e. the triangle) each time you invoke the texture. The
>> torus does not move if you do not tell it to specifically. It does not
>> move by a texture translate.
>>
> 
> Yes, in the usual case of applying an 'object pattern' pigment to an object,
> that's true: The pattern is 3D and created at a specific place in 3D space from
> the object it is given; then the object it's applied to (the surface of that
> object) needs to line up more or less with the pattern in the same space, to see
> *some* effect of it. Both things can be translated individually to get the best
> line-up, AFAIK.
> 
> But I sense that BE's idea is to actually REPEAT the 'object pattern' (or *any*
> pattern) on each and every triangle of a mesh via uv-mapping, even if the mesh
> is some kind of complex rounded form. If so, it's an intriguing idea; I wonder
> if it's possible.
> 
> 
I agree. The idea is intriguing indeed and, when waking up in the middle 
of the night, I thought: "Ah!"  ;-)

I think that the biggest problem BE wants to solve is a contradiction 
between two realities:
1- an object pattern (as embedded in a pigment or a texture) needs a 
3D-intersection between two objects to take effect;
2- using an object pattern (again, as embedded in a pigment or a 
texture) and then uv-mapping that pigment or texture on an object means 
that the necessary 3rd dimension is lost(a). There is no way the texture 
can "know" which switch it should use. uv-mapping is about "mapping" a 
texture "over" a given surface and not intersecting with it.

Again, afaik. I guess we need a real specialist here. ;-)

(a) and in addition, any translation of the object within the pattern is 
not performed.

https://wiki.povray.org/content/Reference:Object_Pattern

The much regretted Friedrich Lohmueller had a clear tutorial about the 
use of object patterns. I used it gratefully last year to pattern my 
Lohmueller truck, as I mentioned elsewhere:

https://news.povray.org/povray.general/message/%3C63f24b8e%40news.povray.org%3E/#%3C63f24b8e%40news.povray.org%3E

-- 
Thomas


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