POV-Ray : Newsgroups : povray.general : QUESTION: STL to POV (INC)? Server Time: 22 Oct 2017 21:00:58 GMT
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From: Kenneth
Subject: Re: QUESTION: STL to POV (INC)?
Date: 19 Aug 2017 22:55:01
Message: <web.5998c0f5db2ef770883fb31c0@news.povray.org>
Sven wrote:
> Blender is a book with seven seals for me...

Ha! That's a good biblical analogy (to someone like me, who hasn't tried
learning even the basics of Blender yet.) I got a good laugh out of that.

Bald Eagle wrote:
> The triangles in a mesh have a "handedness" - an axial chirality.
> Give a "thumbs up" with your left hand, and if you order your triangle
> vertices in the order that your fingers curl, then the normal points up
> like your thumb.

Well-said; much better than my rather clumsy explanation. And "chiraity" is the
word I was trying to think of (in a different newsgroup post.)

Bald Eagle wrote:
> I did a wee bit more digging, and I found this from the megapov docs:

> "To determine if a point is inside a triangle mesh, POV-Ray shoots a ray
> from the point in some arbitrary direction (the default is <1, 0, 0>)...

I actually didn't know (or remember?) that there was a *default* inside_vector.
I should have re-read the docs; it has been awhile re: this topic.

> My guess is that the vector can be supplied as a 'tweak' to override
> the default value in case there are any weird artefacts showing up...

Yes, that makes sense now.


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From: Kenneth
Subject: Re: QUESTION: STL to POV (INC)?
Date: 19 Aug 2017 23:10:01
Message: <web.5998c48cdb2ef770883fb31c0@news.povray.org>
"Kenneth" <kdw### [at] gmailcom> wrote:

>
> Well-said; much better than my rather clumsy explanation. And "chiraity" is the
> word I was trying to think of (in a different newsgroup post.)
>

CHIRALITY. Sorry, I'm tired...


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From: Kenneth
Subject: Re: QUESTION: STL to POV (INC)?
Date: 19 Aug 2017 23:30:01
Message: <web.5998c8c4db2ef770883fb31c0@news.povray.org>
clipka <ano### [at] anonymousorg> wrote:
>
> As a raytracer, POV-Ray's main schtick to render any objects in the
> scene is to compute intersection points between rays (usually
> originating at the camera location) and object surfaces.
>

Ah yes, I had neglected to think about the CAMERA ray. That's the 'missing piece
of the puzzle' in my own understanding of inside_vector, its 'shoot-from'
points, etc. Now, I need to digest all these details...


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From: clipka
Subject: Re: QUESTION: STL to POV (INC)?
Date: 20 Aug 2017 21:04:57
Message: <5999f979$1@news.povray.org>
Am 20.08.2017 um 00:51 schrieb Kenneth:
...
> Bald Eagle wrote:
>> I did a wee bit more digging, and I found this from the megapov docs:
> 
>> "To determine if a point is inside a triangle mesh, POV-Ray shoots a ray
>> from the point in some arbitrary direction (the default is <1, 0, 0>)...
> 
> I actually didn't know (or remember?) that there was a *default* inside_vector.
> I should have re-read the docs; it has been awhile re: this topic.

Not sure where that quote is from, but if it ever was true, it has been
outdated for a long time.

Fact is, in current versions of POV-Ray the default value for the
`inside_vector` parameter is the null vector (`<0,0,0>`), which is used
as a special value to turn off that feature.


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From: Kenneth
Subject: Re: QUESTION: STL to POV (INC)?
Date: 21 Aug 2017 05:40:00
Message: <web.599a6fdcdb2ef770883fb31c0@news.povray.org>
clipka <ano### [at] anonymousorg> wrote:
> Am 20.08.2017 um 00:51 schrieb Kenneth:

> > I actually didn't know (or remember?) that there was a *default*
> > inside_vector.
> > I should have re-read the docs; it has been awhile re: this topic.
>
> Not sure where that quote is from, but if it ever was true, it has been
> outdated for a long time.
>
> Fact is, in current versions of POV-Ray the default value for the
> `inside_vector` parameter is the null vector (`<0,0,0>`), which is used
> as a special value to turn off that feature.

Yes, IIRC that agrees with my own v3.6xx experience using meshes (i.e., there's
no *useful* default inside_vector.) I haven't actually used a mesh in awhile,
though.

BTW, this opens up a small 'can of worms' regarding SHAPES.INC: The various
mesh-generation macros there do not add an inside_vector, which precludes those
meshes being used in (other than union) CSG, as they are not generally #written
to a file but used 'internally' by POV-Ray, so to speak.  However, the
HFCREATE() macro near the end of that file CAN be used to #write a mesh to a
text file for later use-- but it lacks an inside_vector as well. I modified my
own SHAPES.INC file years ago, to add that feature to HFCREATE-- but I currently
can't find it :-( I don't know for sure if an *arbitrary* vector can be added
there, although my own experience was that it worked OK (as I never created an
'open' mesh with Shapes.inc...although a few of the macros may allow open meshes
as an option. I think the 'cylinder mesh' macro may be one. In which case an
arbitrary vector would be hit-or-miss. <0,1,0> would probably work most of the
time, I'm guessing.)

Just wanted to mention this for future thought. And I apologize for getting way
off-topic...


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From: Sven Littkowski
Subject: Re: QUESTION: STL to POV (INC)?
Date: 21 Aug 2017 07:45:55
Message: <599a8fb3$1@news.povray.org>
On 21.08.2017 01:36, Kenneth wrote:
> clipka <ano### [at] anonymousorg> wrote:
>> Am 20.08.2017 um 00:51 schrieb Kenneth:
> 
>>> I actually didn't know (or remember?) that there was a *default*
>>> inside_vector.
>>> I should have re-read the docs; it has been awhile re: this topic.
>>
>> Not sure where that quote is from, but if it ever was true, it has been
>> outdated for a long time.
>>
>> Fact is, in current versions of POV-Ray the default value for the
>> `inside_vector` parameter is the null vector (`<0,0,0>`), which is used
>> as a special value to turn off that feature.
> 
> Yes, IIRC that agrees with my own v3.6xx experience using meshes (i.e., t
here's
> no *useful* default inside_vector.) I haven't actually used a mesh in awh
ile,
> though.
> 
> BTW, this opens up a small 'can of worms' regarding SHAPES.INC: The vario
us
> mesh-generation macros there do not add an inside_vector, which precludes
 those
> meshes being used in (other than union) CSG, as they are not generally #w
ritten
> to a file but used 'internally' by POV-Ray, so to speak.  However, the
> HFCREATE() macro near the end of that file CAN be used to #write a mesh t
o a
> text file for later use-- but it lacks an inside_vector as well. I modifi
ed my
> own SHAPES.INC file years ago, to add that feature to HFCREATE-- but I cu
rrently
> can't find it :-( I don't know for sure if an *arbitrary* vector can be a
dded
> there, although my own experience was that it worked OK (as I never creat
ed an
> 'open' mesh with Shapes.inc...although a few of the macros may allow open
 meshes
> as an option. I think the 'cylinder mesh' macro may be one. In which case
 an
> arbitrary vector would be hit-or-miss. <0,1,0> would probably work most o
f the
> time, I'm guessing.)
> 
> Just wanted to mention this for future thought. And I apologize for getti
ng way
> off-topic...
> 
> 
> 
> 
> 
No problem, it is a good off-topic that I follow with great interest. It
makes this discussion richer.

Besides, this thread has been closed already by me, a few days ago, with
a final statement. There is a new thread, and I invite you all to join
there:
"Solidifying a Mesh Object".

But I am going to open yet another thread, inside the IMAGE group. I
will call it
"The POV-Ray Base on Mars",
and invite you all even more to join this project if you like (yes,
project, it is not just a threat).

---
Diese E-Mail wurde von AVG auf Viren geprüft.
http://www.avg.com


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From: Kenneth
Subject: Re: QUESTION: STL to POV (INC)?
Date: 21 Aug 2017 16:55:00
Message: <web.599b0e41db2ef770883fb31c0@news.povray.org>
Sven Littkowski <I### [at] SvenLittkowskiname> wrote:

>
> Besides, this thread has been closed already by me, a few days ago, with
> a final statement.

No, no, a POV-Ray newsgroup thread should never be consider 'closed'. ;-)  Three
years from now, someone else might read your post and come up with an
important new comment or idea to add, concerning your particular original
question. If the user posts it there, it will then show up in the newsgroups'
'most recent messages' list, for others to see.

My own opinion is that keeping related comments together in one place is
generally a good approach (if they're not off-topic), as it makes it easier to
'search' for a particular specialized topic in the future.

I do newsgroup searches all the time, looking at old posts for 'past wisdom' on
a particular topic (and to try and avoid asking the 'same old question' again.)
The newsgroup archive is a HUGE treasure-trove of interesting and useful topics.


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From: Bald Eagle
Subject: Re: QUESTION: STL to POV (INC)?
Date: 21 Aug 2017 17:10:01
Message: <web.599b1380db2ef770c437ac910@news.povray.org>
clipka <ano### [at] anonymousorg> wrote:

> Not sure where that quote is from, but if it ever was true, it has been
> outdated for a long time.

Yes, MegaPOV version 0.6

https://www.google.com/search?rlz=1C1CHFX_enUS633US634&q=megapov+%22To+determine+if+a+point+is+inside+a+triangle+mesh%2
2&oq=megapov+%22To+determine+if+a+point+is+inside+a+triangle+mesh%22


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From: Stephen
Subject: Re: QUESTION: STL to POV (INC)?
Date: 21 Aug 2017 17:29:19
Message: <599b186f$1@news.povray.org>
On 21/08/2017 17:52, Kenneth wrote:
> Sven Littkowski <I### [at] SvenLittkowskiname> wrote:
> 
>>
>> Besides, this thread has been closed already by me, a few days ago, with
>> a final statement.
> 
> No, no, a POV-Ray newsgroup thread should never be consider 'closed'. ;-)  Three
> years from now, someone else might read your post and come up with an
> important new comment or idea to add, concerning your particular original
> question. If the user posts it there, it will then show up in the newsgroups'
> 'most recent messages' list, for others to see.
> 
> My own opinion is that keeping related comments together in one place is
> generally a good approach (if they're not off-topic), as it makes it easier to
> 'search' for a particular specialized topic in the future.
> 
> I do newsgroup searches all the time, looking at old posts for 'past wisdom' on
> a particular topic (and to try and avoid asking the 'same old question' again.)
> The newsgroup archive is a HUGE treasure-trove of interesting and useful topics.
> 
> 

True. true.

-- 

Regards
     Stephen


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From: clipka
Subject: Re: QUESTION: STL to POV (INC)?
Date: 21 Aug 2017 18:26:05
Message: <599b25bd$1@news.povray.org>
Am 21.08.2017 um 19:08 schrieb Bald Eagle:
> clipka <ano### [at] anonymousorg> wrote:
> 
>> Not sure where that quote is from, but if it ever was true, it has been
>> outdated for a long time.
> 
> Yes, MegaPOV version 0.6
> 
>
https://www.google.com/search?rlz=1C1CHFX_enUS633US634&q=megapov+%22To+determine+if+a+point+is+inside+a+triangle+mesh%2
> 2&oq=megapov+%22To+determine+if+a+point+is+inside+a+triangle+mesh%22

Makes sense: Apparently the feature had originally been introduced in
MegaPOV 0.6(?) with a default value of `<1,0,0>`; when the feature was
later integrated into official POV-Ray, the default seems to have been
deliberately changed to "off", presumably in order to maintain backward
compatibility with previous official versions.


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