POV-Ray : Newsgroups : povray.binaries.images : Unintended behaviour of heightfield in CSG difference? Server Time: 23 Oct 2019 02:03:20 GMT
  Unintended behaviour of heightfield in CSG difference? (Message 1 to 3 of 3)  
From: Bald Eagle
Subject: Unintended behaviour of heightfield in CSG difference?
Date: 9 Oct 2019 00:55:01
Message: <web.5d9d2f8caa18e8744eec112d0@news.povray.org>
So, I was trying out creating a part using an edited blueprint image, and I
needed to use the water_level keyword to remove that bit of base plane.

Then I nearly lost my mind trying to figure out why things "weren't working"
when I tried to difference out a cylinder for nice clean hole - and the cylinder
was VISIBLE - but only on one side... :O

Well, apparently the water_level "deleted" section doesn't get deleted - it just
isn't visible.   But when the cylinder gets differenced from it, that surface
becomes visible, even if the cylinder doesn't have a texture, and the whole CSG
gets an overall texture.

That complicates things more than you'd think, because I do a lot of scaling in
the heightfield definition, and now I have to do that in a separate CSG
operation to difference away a box, or intersect one, etc.


What do we think?   Is this a "bug"?
Has anyone ever seen this before?


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hf part w difference.png


 

From: Thomas de Groot
Subject: Re: Unintended behaviour of heightfield in CSG difference?
Date: 9 Oct 2019 06:46:18
Message: <5d9d823a$1@news.povray.org>
Op 09/10/2019 om 02:53 schreef Bald Eagle:
> 
> 
> What do we think?   Is this a "bug"?
> Has anyone ever seen this before?
> 

I seem to hear a bell tolling in the far distance, muffled by thick mist 
banks... ;-)

Maybe it is best not to use water_level in this particular case and do a 
CSG difference, intersection, or clipping instead. Have you tried that? 
and what is the result?

-- 
Thomas


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From: Alain Martel
Subject: Re: Unintended behaviour of heightfield in CSG difference?
Date: 9 Oct 2019 15:17:26
Message: <5d9dfa06@news.povray.org>
Le 2019-10-08 à 20:53, Bald Eagle a écrit :
> 
> So, I was trying out creating a part using an edited blueprint image, and I
> needed to use the water_level keyword to remove that bit of base plane.
> 
> Then I nearly lost my mind trying to figure out why things "weren't working"
> when I tried to difference out a cylinder for nice clean hole - and the cylinder
> was VISIBLE - but only on one side... :O
> 
> Well, apparently the water_level "deleted" section doesn't get deleted - it just
> isn't visible.   But when the cylinder gets differenced from it, that surface
> becomes visible, even if the cylinder doesn't have a texture, and the whole CSG
> gets an overall texture.
> 
> That complicates things more than you'd think, because I do a lot of scaling in
> the heightfield definition, and now I have to do that in a separate CSG
> operation to difference away a box, or intersect one, etc.
> 
> 
> What do we think?   Is this a "bug"?
> Has anyone ever seen this before?
> 

Instead of water_level, use an intersection with a box. That way, your 
height_field will get a true back side and behave correctly when you 
perform some other CSG operations.


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