[importing the .stl file into CURA, and printing the final model]

The attached image shows the final result: the .stl file brought into my
printer's software (Ultimaker CURA) then printed with medium-quality settings
and a standard 0.4mm print nozzle.

As previously mentioned, this demonstration model was 'sliced' at "low to
medium" quality (from the POV-ray returned messages)-- 522 X 269 pixels, 249
slices. That included a number of black slices at the beginning and end of the
animation. Much better results can be obtained with higher rez images and some
adjustments there. BTW: This model in 3D SLICER ended up having 7,076,000 active
voxels. (None are created from black pixels.)

The honeycomb infill I used-- added in CURA-- was only for supporting any flat
horizontal surfaces in the model, and a few areas on the spheres. Surprisingly,
angled surfaces down to 45-deg from vertical can be printed without supports.

In most cases, the model-as-.stl will be much larger that typical desktop
printers can print-- CURA adds stripes to a model to indicate that it's
oversized-- so it needs to be down-sized in your printing software. This has the
great advantage of reducing the size of the voxel-created triangles--
sharpening-up the model-- and is key to the entire process.

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Attachments:
Download 'final printing via cura-- kw 4_2024.jpg' (521 KB)

Preview of image 'final printing via cura-- kw 4_2024.jpg'

"Kenneth" <kdw### [at] gmailcom> wrote:

> This is a step-by-step guide to 3-D-print almost any type of POV-ray object ....

Well, ... Damn.

You HAVE been busy, haven't you?

Excellent work, fellow Walker!

How's that Creality printer treating you?
Maybe you'll have an FGC9 to print soon   :D


- BE

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Op 6-4-2024 om 13:24 schreef Kenneth:
> See my earlier introductory post about this topic...
> 
>
https://news.povray.org/povray.binaries.images/thread/%3Cweb.655527ca7165e2419b4924336e066e29%40news.povray.org%3E/
> 
> Here it is, finally-- only 5 months late! Real-life got in the way, but I also
> spent time simplifying the required steps and re-writing the 'object slicing'
> code for POV-ray...then tested everything on an almost-daily basis.
> 

Wow! This is a serious piece of work, Kenneth! Well done indeed!

-- 
Thomas

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Thanks BE and Thomas!

You would not *believe* the number of hours I have spent on this project, with
the explanations and code and screenshots-- re-editing almost daily, adding
stuff, erasing stuff, making corrected screenshots, choosing what to include and
what to leave out as unnecessary, making more 3-D test printings etc etc. I kept
telling a few friends that I could probably write a BOOK about it all. But it
sure has been fun :-) For the last couple of weeks, I've been almost
single-minded about finishing it. Now I'm exhausted, ha.

Over the intervening months since last November, I also made some important
discoveries about how 3D SLICER actually works-- by trial and error. My earlier
tests and printed model examples used a much simpler slicing scheme-- which
resulted in squashed-or-stretched results in that app, that I had to re-scale by
eye. Then a 'eureka' moment FINALLY occurred, and my 'automatic' slicing scheme
was the result.

BE: I thought a lot about your earlier suggestion of using POV-ray's 'object
pattern' as a simpler and standard approach to the slicing-- but 3D SLICER's
method of operation makes that approach difficult.  (The proper scaling of the
object there requires a certain number of image slices, not arbitrary like I
originally thought.) A POV-ray object's bounding-box size turned out to be the
answer to that problem-- and object_patterns don't have those. Of course, an
object_pattern has a 1:1 size correspondence with the object it is *made* from,
so I could have used that to get the bounding-box size. Hmm, at some point I
might re-write my code to try that approach!

In some ways, I feel that this entire object-slicing-to-3D-SLICER idea is just
an interim step to the POV-ray 3-D printing problem... waiting for some clever
fellow to take the image-slices and instead create a triangle mesh (and .stl
file) *directly* from the image pixels. Like POV-ray does with height_fields
from a single image, but 'stitching together' all the triangles from all the
slices. Then we would have a direct-to-.stl solution!

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"Kenneth" <kdw### [at] gmailcom> wrote:
>
> In some ways, I feel that this entire object-slicing-to-3D-SLICER idea is just
> an interim step to the POV-ray 3-D printing problem... waiting for some clever
> fellow to take the image-slices and instead create a triangle mesh (and .stl
> file) *directly* from the image pixels.

Well, from the image pixels on the 'outer surfaces' of the white-on-black
slices, the pixels at the outer edges of the object. Possibly using eval_pigment
and a tracing loop, to somehow get all of those pixel positions-- and just
those-- as well as on inner holes and enclosures. I have some half-formed
ideas...

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"Kenneth" <kdw### [at] gmailcom> wrote:

In some ways, I feel that this entire object-slicing-to-3D-SLICER idea is just
an interim step to the POV-ray 3-D printing problem... waiting for some clever
fellow to take the image-slices and instead create a triangle mesh (and .stl
file) *directly* from the image pixels. Like POV-ray does with height_fields
from a single image, but 'stitching together' all the triangles from all the
slices. Then we would have a direct-to-.stl solution!


Well.....  when you convert an image to a heightfield, you already know where
that rectangle is, and you just triangulate it.  Divvy it up into a grid and
then connect the diagonals.  The color dictates the height.

Notice also that you don't have any holes in a heightfield.
Try to make a surface from a photo of Swiss cheese, and you'll begin to
appreciate what the problem is.

In 3D it's even more challenging, because you have internal voids that you need
to find and be aware of.

Now, as for making a mesh, I think that you'd got it twisted around.
The way you're doing it now gives you what you need to 3D print, even if it's
not directly applicable because of the typical workflow.  You need to stack
those layers until you get the full solid object.
Using a mesh or STL, you're actually just storing a shell, which then needs to
get translated to a solid, and then to G-Code to lay out the tool path that
makes those full layers.


So, there are a few challenges that need to be addressed - the first is where is
the object and where is it not?  Trying to do that with trace () is going to
fraught with problems.  Because to map the walls of an internal space, you first
need to know where the internal space IS, in order to start your trace ray at an
appropriate point, but also you still have the problem of you may not be able to
scan a perfectly convex hull, and need to deal with occluding concave
protrusions.

Then once you accumulate all of the scan data, you need to address the issue of
_connectivity_, and I, jr, and other can tell exactly how non-trivial a problem
THAT is.

I personally feel that if we're to have an SDL model-to-mesh library, it's going
to have to use a known method of performing the above tasks accurately and
robustly.
I have also thought about using some sort of Fourier-transform method to convert
the geometry to equations, that could then be used to make the mesh.


Now, your mention of heightfields, and my armchair consideration of those, gave
me an idea.

The concept is this:
(And I'm just laying it out in familiar terms to illustrate the process.   We
could use arrays and inside() tests, and any manner of different practical
implementations to actually achieve the result.)
Let's say you take your slicer method and you now have a slice.  One could scan
the "image" with eval_pigment and see what's white and what's black.  The
position where you switch from one color to the other is obviously an edge.
That would be a triangle vertex.
Once you had all of your slices processed into a point cloud of vertices, you
could scan through it and whatever points were close enough to each other in
different layers, you could connect into triangles.
If there wasn't another layer with a sufficiently close point, you could then
search in the same layer.

Perhaps even if a rudimentary mesh could be made, then something like MeshLab or
other software could clean up the mesh, remove duplicates, close holes, smooth
it, etc.

There are a lot of new and impressive tools like CloudCompare that we might be
able to simply process the raw point cloud with.

And if those techniques work, then we can dig up what algorithms they use to
accomplish those tasks.


- BW

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On 06.04.2024 16:47, Kenneth wrote:

> an interim step to the POV-ray 3-D printing problem... waiting for some clever
> fellow to take the image-slices and instead create a triangle mesh (and .stl
> file) *directly* from the image pixels.

This may be an interesting idea, assuming I can understand that format 
(do I understand it right that you printer requires some STL, and that's 
that STL I'm reading about at 
https://en.wikipedia.org/wiki/STL_(file_format) ?). Sounds like they 
have a text version of it.

The problem I see right now is that we have different number of "outline 
pixels" at every section. Other than that, idea of slicing any object 
into set of planar sections, then reconstructing from this looks brutal 
;-) But the problem is, the number of control points change between 
sections (sometimes they completely disappear), and I don't see a way to 
figure out how to deal with it. But well, it looks like an interesting 
idea to think of in background process.

Ilyich the Toad
https://dnyarri.github.io/

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On 07.04.2024 0:31, Ilya Razmanov wrote:

> The problem I see right now is that we have different number of "outline 
> pixels" at every section.

...on the other hand, if you dissect 3D with planes, who can stop me 
from further dissecting 2D slices thus obtained with scanlines? That may 
be it...

Ilyich the Toad
https://dnyarri.github.io/

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Il 06/04/2024 13:24, Kenneth ha scritto:
> See my earlier introductory post about this topic...
> 
>
https://news.povray.org/povray.binaries.images/thread/%3Cweb.655527ca7165e2419b4924336e066e29%40news.povray.org%3E/
> 
> Here it is, finally-- only 5 months late! Real-life got in the way, but I also
> spent time simplifying the required steps and re-writing the 'object slicing'
> code for POV-ray...then tested everything on an almost-daily basis.
[...]

Wonderful results!

Paolo

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Ilya Razmanov <ily### [at] gmailcom> wrote:
>
> This may be an interesting idea, assuming I can understand that format
> (do I understand it right that you printer requires some STL, and that's
> that STL I'm reading about at
> https://en.wikipedia.org/wiki/STL_(file_format) ?). Sounds like they
> have a text version of it.

Yes, the 3-D printer's software requires the final object to be in the .stl file
format-- either as a text file or a binary one. The 3D SLICER app can only
export it as a binary type, but that can be brought into another app like
Meshmixer to change it to a text file. However, the binary version results in a
much smaller file size. The Wikipedia entry is using the text version as an
example there.
>
> The problem I see right now is that we have different number of "outline
> pixels" at every section. Other than that, idea of slicing any object
> into set of planar sections, then reconstructing from this looks brutal
> ;-) But the problem is, the number of control points change between
> sections (sometimes they completely disappear), and I don't see a way to
> figure out how to deal with it.
>

Yes, it is a mighty big problem to try and solve! (3D SLICER's algorithm changes
them into voxels first-- somehow. But even there, the ultimate voxel-to-triangle
conversion can be a bit...strange... when individual 'naked' voxels are
processed that do not have surrounding neighbors.)

> ...on the other hand, if you dissect 3D with planes, who can stop me
> from further dissecting 2D slices thus obtained with scanlines? That may
> be it...

YES, that is the general idea I have as well. I am going to write some quick
'demonstration' scanning/eval_pigment code to see if I can make it work-- on at
least ONE sliced image. I *should* end up with another image that has just a
white-pixel shell, at only the outer surfaces of the white object as well as at
holes and voids.

This is just an interim step while I continue to think...  ;-)

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