POV-Ray : Newsgroups : povray.programming : IPoint Server Time
25 Feb 2024 03:51:47 EST (-0500)
  IPoint (Message 1 to 7 of 7)  
From: 225012156
Subject: IPoint
Date: 7 Jun 2023 04:00:00
Message: <web.6480385a29d3d13a6cf6dae3fc1cf70c@news.povray.org>
I tried to output the IPoint of each ray, but I found something was not right
I built the following small mesh2Object
camera {
orthographic
location <20.0, 54.949548, 0.0>
look_at <0.0, 0.0, 0.0>
right 100*x
up 100*y
}

light_source {
<20.0, 54.949548, 0.0>
color rgb<1, 1, 1>
parallel
point_at <0.0, 0.0, 0.0>
}


#declare base_02 = mesh2 {
vertex_vectors {
3
<2.952163, 3.632734, -10.591118>,
<1.556791, 3.632964, -10.593109>,
<2.93827, 3.516272, -10.833504>,
}
face_indices {
1
<0,1, 2>,
}
}
union {
object {base_02
texture {
pigment { color rgb<1.0, 1.0, 1.0> }
finish {reflection {0.5} ambient 0 diffuse 0.015 specular 0.7 roughness 0.00085}
}
}
translate <0, 0, 3> //
rotate <0, 0, 0> //
}
Why is its IPoint
1.976229 3.602266-7.656250
2.419499 3.601889-7.656250
2.862769 3.601512-7.656250
I mean, obviously the z coordinate of the mesh2 Object is around -10, but how
does it intersect at -7.656250?


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From: jr
Subject: Re: IPoint
Date: 7 Jun 2023 04:40:00
Message: <web.64804131b3efc58b49d80446cde94f1@news.povray.org>
hi,

"225012156" <225### [at] csueducn> wrote:
> ...
> #declare base_02 = mesh2 {
> vertex_vectors {
> 3
> <2.952163, 3.632734, -10.591118>,
> <1.556791, 3.632964, -10.593109>,
> <2.93827, 3.516272, -10.833504>,
> }
> face_indices {
> 1
> <0,1, 2>,
> }
> }
> union {
> object {base_02
> texture {
> pigment { color rgb<1.0, 1.0, 1.0> }
> finish {reflection {0.5} ambient 0 diffuse 0.015 specular 0.7 roughness 0.00085}
> }
> }
> translate <0, 0, 3> //
> rotate <0, 0, 0> //
> }
> Why is its IPoint
> 1.976229 3.602266-7.656250
> 2.419499 3.601889-7.656250
> 2.862769 3.601512-7.656250
> I mean, obviously the z coordinate of the mesh2 Object is around -10, but how
> does it intersect at -7.656250?

hope I interpret correctly, but is -10 + (translate 3) not 7 ?  :-)


regards, jr.


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From: 225012156
Subject: Re: IPoint
Date: 7 Jun 2023 04:55:00
Message: <web.64804559b3efc586cf6dae3fc1cf70c@news.povray.org>
"jr" <cre### [at] gmailcom> wrote:
> hi,
>
> "225012156" <225### [at] csueducn> wrote:
> > ...
> > #declare base_02 = mesh2 {
> > vertex_vectors {
> > 3
> > <2.952163, 3.632734, -10.591118>,
> > <1.556791, 3.632964, -10.593109>,
> > <2.93827, 3.516272, -10.833504>,
> > }
> > face_indices {
> > 1
> > <0,1, 2>,
> > }
> > }
> > union {
> > object {base_02
> > texture {
> > pigment { color rgb<1.0, 1.0, 1.0> }
> > finish {reflection {0.5} ambient 0 diffuse 0.015 specular 0.7 roughness 0.00085}
> > }
> > }
> > translate <0, 0, 3> //
> > rotate <0, 0, 0> //
> > }
> > Why is its IPoint
> > 1.976229 3.602266-7.656250
> > 2.419499 3.601889-7.656250
> > 2.862769 3.601512-7.656250
> > I mean, obviously the z coordinate of the mesh2 Object is around -10, but how
> > does it intersect at -7.656250?
>
> hope I interpret correctly, but is -10 + (translate 3) not 7 ?  :-)
>
>
> regards, jr.

Thank you.I also found this mistake after sending this message. Sorry to bother
you with such a small problem


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From: ingo
Subject: Re: IPoint
Date: 7 Jun 2023 05:15:00
Message: <web.648049a9b3efc5817bac71e8ffb8ce3@news.povray.org>
"225012156" <225### [at] csueducn> wrote:

> I mean, obviously the z coordinate of the mesh2 Object is around -10, but how
> does it intersect at -7.656250?

maybe because of translate <0, 0, 3>?

ingo


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From: jr
Subject: Re: IPoint
Date: 7 Jun 2023 06:05:00
Message: <web.6480559bb3efc58b49d80446cde94f1@news.povray.org>
hi,
"225012156" <225### [at] csueducn> wrote:
> ...
> Thank you.I also found this mistake after sending this message. Sorry to bother
> you with such a small problem

no problem.  (I see such "slip ups" to mean that a (short) break, to have a
coffee or doing something else, is due.  ;-))


regards ,jr.


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From: kurtz le pirate
Subject: Re: IPoint
Date: 10 Jun 2023 05:21:05
Message: <64844081$1@news.povray.org>
On 07/06/2023 11:11, ingo wrote:
> "225012156" <225### [at] csueducn> wrote:
> 
>> I mean, obviously the z coordinate of the mesh2 Object is around -10, but how
>> does it intersect at -7.656250?
> 
> maybe because of translate <0, 0, 3>?

yes, translate, but POVRay say :
-10.591118 + 3.000000 = -7.591118

and "225012156" wrote that z is equal to -7.656250
so a gap of 0.065132.

another subtlety ?






-- 
Kurtz le pirate
Compagnie de la Banquise


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From: Bald Eagle
Subject: Re: IPoint
Date: 10 Jun 2023 08:10:00
Message: <web.648467d5b3efc581f9dae3025979125@news.povray.org>
kurtz le pirate <kur### [at] gmailcom> wrote:

> yes, translate, but POVRay say :
> -10.591118 + 3.000000 = -7.591118
>
> and "225012156" wrote that z is equal to -7.656250
> so a gap of 0.065132.
>
> another subtlety ?

There are two vertices with z = -10.591118
and one with z = -10.833504


#declare base_02 = mesh2 {
vertex_vectors {
3
<2.952163, 3.632734, -10.591118>,
<1.556791, 3.632964, -10.593109>,
<2.93827, 3.516272, -10.833504>,
}


So it's not completely vertical, which means the intersection point will be
farther back than -10.591118.  The z coordinate of the centroid of the
translated triangle lies at  -7.67195467, but maybe it's intersecting at one of
the other triangle centers.

- BE


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