POV-Ray : Newsgroups : povray.general : Did I miss anything? (parent/child texture in CSG) : Re: Did I miss anything? (parent/child texture in CSG) Server Time
3 Mar 2024 16:57:10 EST (-0500)
  Re: Did I miss anything? (parent/child texture in CSG)  
From: William F Pokorny
Date: 1 Feb 2024 08:19:55
Message: <65bb9a7b$1@news.povray.org>
On 2/1/24 07:19, Bald Eagle wrote:
> I always thought that once the object was textured, it was fixed, and could not
> be overridden.  This has been discussed in the past, so I'm surprised.  I also
> do a lot of scenes where I have some objects in a union textured/pigmented and
> then the union gets a texture/pigment, and only the default textured objects get
> the union texture.

It can be confusing and we're not helped due some of the documentation 
being misleading.

Internally what happens is things not explicitly textured with 
texture{}(s) / material{} or by creating a texture via one of the fast 
path / shorthand texture component texture specifications, like a not 
texture{} wrapped color or pigment{} block specification, are not 
textured at all until a post process step of the parsing.

In that post step the parent 'stuff' which exists is pushed down onto 
the children - or the default texture gets applied - where there isn't 
already 'stuff'. (lying a little)

The thing about the fast path texture component methods is they 
sometimes assign the default texture and modify a particular component 
of it. Or, they modify a particular component of the existing attached 
texture. Supposing an already textured Tor00 and Tor01 with no texture.

object { Tor00 pigment{...} } // Modifies the already attached texture.
object { Tor01 pigment{...} } // Modifies / applies default texture

object { Tor00
// Replaces attached texture with modified, default texture. The
// texture{} wrap without a passed texture ID always starts with the
// default texture.
   texture { pigment {...} }
}

Aside: Good memory on the torus uv mapping! :-) One of the three forms 
was mistakenly created right handed. I do still flip it to left handed 
as I recall in the yuqk code. The official v3.8 POV-Ray releases left 
the mapping code as is. At the moment, not sure how it could be related, 
but maybe? I'm in the middle of some other code work, so the 
investigation on the spiral 1 & 2  won't happen for a while.

Bill P.


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