POV-Ray : Newsgroups : povray.newusers : Non- exsistent object are white, but not transparent Server Time: 19 Dec 2018 13:42:46 GMT
  Non- exsistent object are white, but not transparent (Message 1 to 5 of 5)  
From: stein
Subject: Non- exsistent object are white, but not transparent
Date: 26 Mar 2018 13:15:00
Message: <web.5ab8f1a5c715f2fdd8a52b4d0@news.povray.org>
I have a cone-like object as a Mesh2 object:

https://imgur.com/a/5u1XC (picture)
https://pastebin.com/aC5aQCg1 (textfile)

and i would like to cut away the part which is positive in x and y. For this I
am using an intersection with 3 boxes. The desired part is white, but not
transparent.

https://imgur.com/a/6htgs (picture)
https://pastebin.com/q5fZnHqu (file with intersection)

How do I force POVRay to look into the cone?


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From: William F Pokorny
Subject: Re: Non- exsistent object are white, but not transparent
Date: 26 Mar 2018 13:46:37
Message: <5ab8f9bd@news.povray.org>
On 03/26/2018 09:12 AM, stein wrote:
> I have a cone-like object as a Mesh2 object:
> 
> https://imgur.com/a/5u1XC (picture)
> https://pastebin.com/aC5aQCg1 (textfile)
> 
> and i would like to cut away the part which is positive in x and y. For this I
> am using an intersection with 3 boxes. The desired part is white, but not
> transparent.
> 
> https://imgur.com/a/6htgs (picture)
> https://pastebin.com/q5fZnHqu (file with intersection)
> 
> How do I force POVRay to look into the cone?
> 

Somewhat of a guess, but CSG with meshes requires closed meshes that 
also include an inside_vector (a direction vector) specification to be 
able to determine what is inside vs outside. Your mesh appears to be 
open at the top.

Maybe... you can do what you want with your open mesh if you specify an 
inside_vector running parallel to the opening at the top and otherwise, 
as usual for the inside_vector, NOT running parallel to any of the mesh 
faces. Might not work too depending on other 'stuff.'

Another - likely more robust - option would be to close the top with 
faces that are themselves transparent after which an inside_vector 
should work without the extra top-parallel restriction.

Bill P.


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From: Bald Eagle
Subject: Re: Non- exsistent object are white, but not transparent
Date: 26 Mar 2018 16:25:01
Message: <web.5ab91e04ce96c6d1c437ac910@news.povray.org>
"stein" <nomail@nomail> wrote:
> I have a cone-like object as a Mesh2 object:
>
> https://imgur.com/a/5u1XC (picture)
> https://pastebin.com/aC5aQCg1 (textfile)
>
> and i would like to cut away the part which is positive in x and y. For this I
> am using an intersection with 3 boxes. The desired part is white, but not
> transparent.
>
> https://imgur.com/a/6htgs (picture)
> https://pastebin.com/q5fZnHqu (file with intersection)
>
> How do I force POVRay to look into the cone?

Very quickly - I would do what WP suggested, and make sure you have an inside
vector defined in your mesh.

After you do that, I'd do a few other things.

First, put your mesh into a separate include file.
(this will make your actual scene MUCH smaller and readable)
Second, get the min and max extents (I'll call them <X1, Y1, Z1> and <X2, Y2,
Z2> of your bounding box for the mesh.
then you can define your intersection with a box that's always the region you
want regardless of your scaling of the mesh:

box {<0, 0, Z1>, <X2, Y2, Z2>}

Lastly, give the box an rgbt transparent pigment, so that the pigment inherited
by the intersection face is transparent.

intersection{
     object {YourMesh}
     box {<0, 0, Z1>, <X2, Y2, Z2> pigment {rgbt 1}}
}


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From: Alain
Subject: Re: Non- exsistent object are white, but not transparent
Date: 26 Mar 2018 17:33:25
Message: <5ab92ee5@news.povray.org>
Le 18-03-26 à 09:12, stein a écrit :
> I have a cone-like object as a Mesh2 object:
> 
> https://imgur.com/a/5u1XC (picture)
> https://pastebin.com/aC5aQCg1 (textfile)
> 
> and i would like to cut away the part which is positive in x and y. For this I
> am using an intersection with 3 boxes. The desired part is white, but not
> transparent.
> 
> https://imgur.com/a/6htgs (picture)
> https://pastebin.com/q5fZnHqu (file with intersection)
> 
> How do I force POVRay to look into the cone?
> 
> 

It looks like you want to clip out some parts of your mesh.
If that's the case, then, you don't need the inside_verctor, in fact, 
you *don't want* to use one.
Using a difference would be simpler and easier than your intersection of 
a mesh and 3 boxes.
Replacing your mesh with an identifier to have something more concise, 
you can have something like this :

difference{
  object{My_Mesh}
// mesh WITHOUT an inside_vector and without any texture !
  box{<0,-10,0><-10, 10, -10>}// NO pigment !
  pigment{radial}
}

This example assume that the axis of your shape sits around the Y axis, 
change the box to accommodate your reference system if needed.
This way, the mesh is ONLY a zero thickness surface.
The procedural texture similar to the one that you use is applied to the 
whole object at once.
The radial pattern have a default colour_map that matches your image, so 
I did not include one.
As the CSG object don't have any thickness, the box will not show.

Another way is to use clipped_by :

object{My_Mesh
	clipped_by{box{<0,-10,0><-10, 10, -10>}}
	pigment{radial}
}

clipped_by cut out the part that is inside the clipper object.
Even is the clipped object is solid, like a box, you'll only see it as a 
shell.



Alain


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From: stein
Subject: Re: Non- exsistent object are white, but not transparent
Date: 27 Mar 2018 08:40:00
Message: <web.5aba0306ce96c6d1d8a52b4d0@news.povray.org>
Alain <kua### [at] videotronca> wrote:
> Le 18-03-26 à 09:12, stein a écrit :
> > I have a cone-like object as a Mesh2 object:
> >
> > https://imgur.com/a/5u1XC (picture)
> > https://pastebin.com/aC5aQCg1 (textfile)
> >
> > and i would like to cut away the part which is positive in x and y. For this I
> > am using an intersection with 3 boxes. The desired part is white, but not
> > transparent.
> >
> > https://imgur.com/a/6htgs (picture)
> > https://pastebin.com/q5fZnHqu (file with intersection)
> >
> > How do I force POVRay to look into the cone?
> >
> >
>
> It looks like you want to clip out some parts of your mesh.
> If that's the case, then, you don't need the inside_verctor, in fact,
> you *don't want* to use one.
> Using a difference would be simpler and easier than your intersection of
> a mesh and 3 boxes.
> Replacing your mesh with an identifier to have something more concise,
> you can have something like this :
>
> difference{
>   object{My_Mesh}
> // mesh WITHOUT an inside_vector and without any texture !
>   box{<0,-10,0><-10, 10, -10>}// NO pigment !
>   pigment{radial}
> }
>
> This example assume that the axis of your shape sits around the Y axis,
> change the box to accommodate your reference system if needed.
> This way, the mesh is ONLY a zero thickness surface.
> The procedural texture similar to the one that you use is applied to the
> whole object at once.
> The radial pattern have a default colour_map that matches your image, so
> I did not include one.
> As the CSG object don't have any thickness, the box will not show.
>
> Another way is to use clipped_by :
>
> object{My_Mesh
>  clipped_by{box{<0,-10,0><-10, 10, -10>}}
>  pigment{radial}
> }
>
> clipped_by cut out the part that is inside the clipper object.
> Even is the clipped object is solid, like a box, you'll only see it as a
> shell.
>
>
>
> Alain

I used Alains "clipped_by"-version and this worked very well.  I only had to
invert the box.

object{My_Mesh
 clipped_by{box{<0,0,0><10, 10, 10> inverse}}
}


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