Aside: I have been playing a bit with object patterns but I must confess 
that I do not understand them... :-/

-- 
Thomas

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Thomas de Groot <tho### [at] degrootorg> wrote:
> Aside: I have been playing a bit with object patterns but I must confess
> that I do not understand them... :-/
>
> --
> Thomas

One would assume that you've checked out FM's pages:
http://www.f-lohmueller.de/pov_tut/tex/tex_560e.htm
http://www.f-lohmueller.de/pov_tut/tex/tex_561e.htm
http://www.f-lohmueller.de/pov_tut/tex/tex_562e.htm

It looks like it's analagous to texture vs inside_texture in that it chooses one
texture or another. With this, it's not what "side" it on, it's whether or not
the point is any part of the object or not at all.

So presumably a[nother] good test scene would be a small object inside a
transmissive sphere - with the sphere representing the outside environment of
the object, and the object the inside.

[As with the rest of life] I find the pictures very helpful in understanding
what's going on.  When it's all text and I have to sound it out, people think
I'm talking to myself in some made up language...

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Am 04.10.2017 um 13:47 schrieb Thomas de Groot:
> Aside: I have been playing a bit with object patterns but I must confess
> that I do not understand them... :-/

They're pretty simple:

- Just like the `brick` or `checker` patterns, the `object` pattern is a
"choose one of two" pattern (as opposed to a "choose from a map" pattern
like `gradient`).

- You specify an arbitrary solid shape (may be CSG) to govern the actual
pattern, and every point in pattern 3D coordinate space is textured
according to whether it would be inside that shape or outside.


Think of this pattern as follows:

- Take the object specified in the pattern.
- Using vacuum forming, create a template from the pattern object.
- Discard the pattern object.
- Pour material A into the template.
- Pour material B around the template.

This creates a solid block, partially made from material A, and
partially made from material B, which is now your texture (or pigment).

- From the resulting block, carve an entirely different shape (the
actual object that uses the `object` pattern)

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"Norbert Kern" <nor### [at] t-onlinede> wrote:
> Recent posts here renewed my interest in proximity patterns.

That's some wild stuff there. Brings a whole new dimension to that one object.

Going to those past messages about this sort of thing shows what I was missing
out on when I decided to do more RL things (sightseeing motorcycle rides for
one).

I must make more of my own (even if feeble) attempts at this proximity pattern
thing too!

Thanks for the look!

Bob

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On 4-10-2017 17:46, clipka wrote:
> Am 04.10.2017 um 13:47 schrieb Thomas de Groot:
>> Aside: I have been playing a bit with object patterns but I must confess
>> that I do not understand them... :-/
> 
> They're pretty simple:
> 

Thanks Clipka and Bald Eagle; I indeed forgot to consult FL ;-)

I fully understand now.


-- 
Thomas

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Thank you for the comments.

I just downloaded the demo file with 25 proximity materials on
povray.binaries.scene-files
(http://news.povray.org/povray.binaries.scene-files/thread/%3Cweb.59d7a90b58cfc649473ac47e0%40news.povray.org%3E/).

It's a 4 part download because of mesh size.

By the way - here is another render with 2 extremely large meshes (600 MB for
the Napoleon statue and 400 MB for the dragon figure in mesh2 formate).
It took several trials with different PoseRay versions to transform the basic
obj files (coming from Artec 3D -
https://www.artec3d.com/3d-models/art-and-design).

What are your experiences with large models - are there ways to improve
stability of the mesh conversion?

Regards
Norbert

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Attachments:
Download 'napoleon & dragon_prox.jpg' (446 KB)

Preview of image 'napoleon & dragon_prox.jpg'

On 6-10-2017 19:01, Norbert Kern wrote:
> Thank you for the comments.
> 
> I just downloaded the demo file with 25 proximity materials on
> povray.binaries.scene-files
>
(http://news.povray.org/povray.binaries.scene-files/thread/%3Cweb.59d7a90b58cfc649473ac47e0%40news.povray.org%3E/).
> 
> It's a 4 part download because of mesh size.
> 
> By the way - here is another render with 2 extremely large meshes (600 MB for
> the Napoleon statue and 400 MB for the dragon figure in mesh2 formate).
> It took several trials with different PoseRay versions to transform the basic
> obj files (coming from Artec 3D -
> https://www.artec3d.com/3d-models/art-and-design).
> 
> What are your experiences with large models - are there ways to improve
> stability of the mesh conversion?
> 

Thanks for this Norbert.

Concerning conversion of very large models/meshes (from obj to mesh2), I 
seem to remember issues with them in Poseray. However - now that I think 
about it - they mainly concerned using subdivision levels and thus 
crashing Poseray. It may be something to talk about with FlyerX. With 
meshes becoming more complex alongside faster hardware and more memory, 
there might come a moment when Poseray will need an upgrade (rather than 
an update?).

-- 
Thomas

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Am 10/6/2017 um 19:01 schrieb Norbert Kern:
> 
> What are your experiences with large models - are there ways to improve
> stability of the mesh conversion?
> 
PoseRay is a 32bit Application and as such can't handle huge meshes. 
Disabling it's OpenGL preview (within the Preview pane) helps and allows 
for converting meshes that would otherwise crash it - up to some point.
Personally I prefer Blender (64bit) for converting meshes to POV-Ray 
format - if needed.

-Ive

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I was thinking about this from entirely another angle:

Currently the object pattern can give us results based on inside vs outside of a
3D object.

Is there [no] ... could there be a way [in the future] to do something similar
to this where the _surface_ of the object is a result?

If this could be implemented in a way that a pattern function could take
advantage of that, then you could make an isosurface of any object, and then you
could scale it nonlinearly - which AFAIK is not currently possible.

http://www.econym.demon.co.uk/isotut/substitute.htm

It would also instantly provide a method to convert an object into a mesh using
one of the isosurface approximation methods.
And loads of people would LOVE to have that at their fingertips.

With regard to that aspect, if a surface pattern is too long off in the future,
is there a way to do a ray-object intersection "function" that returns the
crossing number
https://en.wikipedia.org/wiki/Point_in_polygon
AND an array that has the coordinates of the crossing points?

Because that would provide a powerful method to construct meshes, and do all
sorts of other analyses and manipulations on objects.

Just asking out of curiosity, since it seems these features aren't that
different from what's available already or happens internally.

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Le 12/10/2017 à 03:41, Bald Eagle a écrit :
> I was thinking about this from entirely another angle:
> 
> Currently the object pattern can give us results based on inside vs outside of a
> 3D object.
> 
> Is there [no] ... could there be a way [in the future] to do something similar
> to this where the _surface_ of the object is a result?

Computing the shortest distance from a point to an object might not be
trivial, it might require a new function for each shape (in addition to
the inside test and the computation of intersections with a ray).

And I'm not sure transformations are compatible with such gradient
field. (especially shearing transform). Traditionally, the ray is
applied the inverse transform of the object, computation is done, and
result is applied the transform to get back in SDL space. But when
transformation is not conserving distance, it is a big problem for a
*surface* pattern.

Neither what to do for CSG difference & intersection.
(CSG union & merge are easy: min() )

> 
> If this could be implemented in a way that a pattern function could take
> advantage of that, then you could make an isosurface of any object, and then you
> could scale it nonlinearly - which AFAIK is not currently possible.
> 
> http://www.econym.demon.co.uk/isotut/substitute.htm
> 
> It would also instantly provide a method to convert an object into a mesh using
> one of the isosurface approximation methods.
> And loads of people would LOVE to have that at their fingertips.
> 
> With regard to that aspect, if a surface pattern is too long off in the future,
> is there a way to do a ray-object intersection "function" that returns the
> crossing number
> https://en.wikipedia.org/wiki/Point_in_polygon
> AND an array that has the coordinates of the crossing points?

Did you read http://paulbourke.net/geometry/polygonise/ ?



> 
> Because that would provide a powerful method to construct meshes, and do all
> sorts of other analyses and manipulations on objects.

Did you see some experimentations in hgpovray :

> http://wiki.povray.org/content/User:Le_Forgeron#Tesselation_.26_mesh_play

6 ways to get a mesh from a solid.

And many transformations:
> http://wiki.povray.org/content/User:Le_Forgeron#Getting_a_new_mesh_from_a_mesh



> 
> Just asking out of curiosity, since it seems these features aren't that
> different from what's available already or happens internally.
> 
> 
> 
>

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