Cant smooth this domed end

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Cant smooth this domed end

andy_at_blighty

Below is a very cut down sample of my model… which in reality is doing rotate_extrude on a DXF.

 

It creates a cylinder with a shallow dome on the end. The trouble is that I seem to be unable to smooth out the ‘tree rings’ on the end sufficiently.

 

If I reduce $fa to 0.5 then the end becomes coarser instead of smoother. I’ve also experimented with $fn and the end gets smoother up to a value of about 570 and then it gets worse. Messing with $fs doesn’t seem to help either.

 

Is there anything I can do to get past this problem?

 

$fs=.05;

$fa=.632;

 

rotate_extrude(convexity=10) {

    intersection() {

        circle(16.9);

        translate([-3,0,0]) {

            square([3,20]);

        }

    }

}

 

Regards,

Andy


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Re: Cant smooth this domed end

nophead
How smooth do you need it? It looks very smooth to me with $fn = 1000.

image.png

On Thu, 10 Jan 2019 at 18:56, Andy Carlson <[hidden email]> wrote:

Below is a very cut down sample of my model… which in reality is doing rotate_extrude on a DXF.

 

It creates a cylinder with a shallow dome on the end. The trouble is that I seem to be unable to smooth out the ‘tree rings’ on the end sufficiently.

 

If I reduce $fa to 0.5 then the end becomes coarser instead of smoother. I’ve also experimented with $fn and the end gets smoother up to a value of about 570 and then it gets worse. Messing with $fs doesn’t seem to help either.

 

Is there anything I can do to get past this problem?

 

$fs=.05;

$fa=.632;

 

rotate_extrude(convexity=10) {

    intersection() {

        circle(16.9);

        translate([-3,0,0]) {

            square([3,20]);

        }

    }

}

 

Regards,

Andy

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Re: Cant smooth this domed end

nophead
Which version of OpenSCAD are you using? There used to be a bug which limited the fine detail of 2D objects. That might have caused tree rings.

On Thu, 10 Jan 2019 at 19:02, nop head <[hidden email]> wrote:
How smooth do you need it? It looks very smooth to me with $fn = 1000.

image.png

On Thu, 10 Jan 2019 at 18:56, Andy Carlson <[hidden email]> wrote:

Below is a very cut down sample of my model… which in reality is doing rotate_extrude on a DXF.

 

It creates a cylinder with a shallow dome on the end. The trouble is that I seem to be unable to smooth out the ‘tree rings’ on the end sufficiently.

 

If I reduce $fa to 0.5 then the end becomes coarser instead of smoother. I’ve also experimented with $fn and the end gets smoother up to a value of about 570 and then it gets worse. Messing with $fs doesn’t seem to help either.

 

Is there anything I can do to get past this problem?

 

$fs=.05;

$fa=.632;

 

rotate_extrude(convexity=10) {

    intersection() {

        circle(16.9);

        translate([-3,0,0]) {

            square([3,20]);

        }

    }

}

 

Regards,

Andy

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Re: Cant smooth this domed end

andy_at_blighty
In reply to this post by andy_at_blighty

Thanks for the replies and sorry if this starts a second thread – I seem to be blocked from replying on the web.

 

I am using 2015.03-2 on Windows which seems rather old but according to the web site it’s the latest version.

 

Your image looks plenty smooth – basically when I get these things 3d printed the ‘tree rings’ are visible and I’d rather they were not.

 

I don’t get a smoother result at $fn=1000. 570 is about as good as it gets and has about 16 concentric rings.

 

I can’t really use $fn on the proper model because there are also small radius curves and having so many facets on a small curve will push up the model complexity too much.

 

The attached image has the contrast pushed up to hopefully show what I get.

 

Is there a later version? Are the dev snapshots suitable for everyday use for example?

 

Regards, Andy


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tree-rings (2).png (82K) Download Attachment
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Re: Cant smooth this domed end

nophead
Yes I have been using snapshots for years with few problems.

On Thu, 10 Jan 2019 at 19:53, Andy Carlson <[hidden email]> wrote:

Thanks for the replies and sorry if this starts a second thread – I seem to be blocked from replying on the web.

 

I am using 2015.03-2 on Windows which seems rather old but according to the web site it’s the latest version.

 

Your image looks plenty smooth – basically when I get these things 3d printed the ‘tree rings’ are visible and I’d rather they were not.

 

I don’t get a smoother result at $fn=1000. 570 is about as good as it gets and has about 16 concentric rings.

 

I can’t really use $fn on the proper model because there are also small radius curves and having so many facets on a small curve will push up the model complexity too much.

 

The attached image has the contrast pushed up to hopefully show what I get.

 

Is there a later version? Are the dev snapshots suitable for everyday use for example?

 

Regards, Andy

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Re: Cant smooth this domed end

andy_at_blighty

Thanks. I tried out the snapshot build.

 

The good news is that it makes a lovely job of my simple example with $fa set to 0.3… which is equivalent to $fn=1200

 

The not so good news is that the tree rings remain just as bad when doing a rotate_extrude of the DXF with the same setting, same cylinder and dome diameter.

 

I will need to experiment some more another day. If all else fails I may need to drop the DXF and draw the end using code.

 

Regards Andy

 

 

 

From: nophead [via OpenSCAD] [[hidden email]]
Sent: 10 January 2019 20:08
To: andy_at_blighty <[hidden email]>
Subject: Re: Cant smooth this domed end

 

Yes I have been using snapshots for years with few problems.

 

 


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Re: Cant smooth this domed end

cbernhardt
In reply to this post by andy_at_blighty
What type of entities (Lines, Arcs, Polylines) are in your DXF file?
Not sure if this is your problem, but if you have Polylines (joined Line and
ARC segments) in the DXF file Openscad seems to interpret the Arc segments
as straight line segments.  You may need to explode the Polylines before
creating the DXF file.



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Re: Cant smooth this domed end

andy_at_blighty

They are arcs. The domed end is an arc and then there are small radius fillets between that and the sides of the cylinder.

 

I’ve now done some more on this. I lifted all of the coordinates from CAD and redid the whole shape using OpenSCAD primitives.

 

The good news is that it then became super-smooth in my test.

 

The not so good news is that I then pasted the exact same code into my real model, removed the DXF extrude… and the tree-rings were still there. The render time also went up from about 2 minutes to 30.

 

So I’m stuck now. I can’t really offer my entire model as a test case (and it would be a pretty unusable test case if I did). At the moment I think my best option is to set $fa to 0.65 (the lowest value that improves the tree-rings) and go for a 3d print with that.

 

Regards, Andy

 

 

 

 

 

From: cbernhardt [via OpenSCAD] [mailto:[hidden email]]
Sent: 11 January 2019 13:44
To: andy_at_blighty <[hidden email]>
Subject: Re: Cant smooth this domed end

 

What type of entities (Lines, Arcs, Polylines) are in your DXF file?
Not sure if this is your problem, but if you have Polylines (joined Line and
ARC segments) in the DXF file Openscad seems to interpret the Arc segments
as straight line segments.  You may need to explode the Polylines before
creating the DXF file.



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Re: Cant smooth this domed end

JordanBrown

Note also that if this dome is at the top of the print, your ability to avoid tree rings is dependent on the Z resolution of your printer.



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Re: Cant smooth this domed end

andy_at_blighty

Yes there are all sorts of questions about printer resolution and artefacts. I’ve actually had this done on two different printer technologies and with different orientations.

 

My main concern with the model is to make sure it is not contributing to any artefacts.

 

Regards, Andy

 

From: JordanBrown [via OpenSCAD] [mailto:[hidden email]]
Sent: 11 January 2019 18:05
To: andy_at_blighty <[hidden email]>
Subject: Re: Cant smooth this domed end

 

Note also that if this dome is at the top of the print, your ability to avoid tree rings is dependent on the Z resolution of your printer.

 


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Re: Cant smooth this domed end

cbernhardt
In reply to this post by andy_at_blighty
Could you post a link to your code that uses rotate_extrude of the DXF file
and also a link to your DXF file?



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Re: Cant smooth this domed end

andy_at_blighty
Not sure if I can attach a DXF but will have a try...

The code is very simple. It has a general setting for $fs and $fa (as per my
real model which uses these values for other parts) . Then $fa is overridden
for the domed end DXF

$fs=.05;
$fa=2;

profdxf = "end-dome.dxf";

rotate_extrude(convexity=10) {
    import(profdxf,$fa=.3);
}

If I mess with the $fa value on the DXF import then the tree rings get more
in number and smaller down to about $fa=0.65 but as I go lower they don't
continue this behaviour. At 0.3 for example I see irregular sizes of ring -
for example the first complete ring outside the centre is a good deal
narrower than the second. I've attached an image - again with the contrast
increased.

Regards Andy


-----Original Message-----
From: Discuss [mailto:[hidden email]] On Behalf Of
cbernhardt
Sent: 11 January 2019 19:53
To: [hidden email]
Subject: Re: [OpenSCAD] Cant smooth this domed end

Could you post a link to your code that uses rotate_extrude of the DXF file
and also a link to your DXF file?



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end-dome.dxf (79K) Download Attachment
treerings-at-0.3fa-contrast-pushed.png (60K) Download Attachment
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Re: Cant smooth this domed end

cbernhardt
I tried your model using your DXF file with many different values of $fn,
$fa, and $fs and it seems that OpenSCAD does apply these variables to arcs
in DXF files the same way as it applies them to objects created by OpenSCAD.
I took your DXF file and did a linear_extrude using various values of $fn.
The picture below shows the STL files of the results.  Looks like 360 is the
upper limit for $fn when inserting a DXF file.  I also tried various values
of $fs and $fa with similar results.
<http://forum.openscad.org/file/t1309/arcs.jpg>



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Re: Cant smooth this domed end

andy_at_blighty
Thanks... kinda glad it's not just me.

As I found earlier, the behaviour is not limited to DXFs. The simple model
using OpenSCAD primitives comes out really smoothly at $fa=0.3 but when I
put it back into the full model it shows the same issue again.

I don't know what makes the difference - it's a complex model and it would
take a lot of messing around to pin it down - maybe the overall complexity
of the model or perhaps the fact that there are still several other DXFs
being rotate_extruded to draw other parts of the same model. If it's the
latter then there is no way I'm going to redraw them all with primitives.

Regards, Andy

-----Original Message-----
From: Discuss [mailto:[hidden email]] On Behalf Of
cbernhardt
Sent: 12 January 2019 18:20
To: [hidden email]
Subject: Re: [OpenSCAD] Cant smooth this domed end

I tried your model using your DXF file with many different values of $fn,
$fa, and $fs and it seems that OpenSCAD does apply these variables to arcs
in DXF files the same way as it applies them to objects created by OpenSCAD.
I took your DXF file and did a linear_extrude using various values of $fn.
The picture below shows the STL files of the results.  Looks like 360 is the
upper limit for $fn when inserting a DXF file.  I also tried various values
of $fs and $fa with similar results.
<http://forum.openscad.org/file/t1309/arcs.jpg>



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Re: Cant smooth this domed end

andy_at_blighty
I just tried combining the primitives version and the DXF version in a
single file. Both use the same value for $fa (0.3).

The primitives one comes out smooth and right next to it is the DXF one with
tree rings.

So scratch the theory that the presence of another DXF in the same model
causes the primitives version to show tree rings... perhaps it's the
complexity that does it or something else in my full model.

I'll spare you the contrast enhanced PNG.

Regards, Andy

-----Original Message-----
From: Discuss [mailto:[hidden email]] On Behalf Of Andy
Carlson
Sent: 12 January 2019 18:34
To: 'OpenSCAD general discussion' <[hidden email]>
Subject: Re: [OpenSCAD] Cant smooth this domed end

Thanks... kinda glad it's not just me.

As I found earlier, the behaviour is not limited to DXFs. The simple model
using OpenSCAD primitives comes out really smoothly at $fa=0.3 but when I
put it back into the full model it shows the same issue again.

I don't know what makes the difference - it's a complex model and it would
take a lot of messing around to pin it down - maybe the overall complexity
of the model or perhaps the fact that there are still several other DXFs
being rotate_extruded to draw other parts of the same model. If it's the
latter then there is no way I'm going to redraw them all with primitives.

Regards, Andy

-----Original Message-----
From: Discuss [mailto:[hidden email]] On Behalf Of
cbernhardt
Sent: 12 January 2019 18:20
To: [hidden email]
Subject: Re: [OpenSCAD] Cant smooth this domed end

I tried your model using your DXF file with many different values of $fn,
$fa, and $fs and it seems that OpenSCAD does apply these variables to arcs
in DXF files the same way as it applies them to objects created by OpenSCAD.
I took your DXF file and did a linear_extrude using various values of $fn.
The picture below shows the STL files of the results.  Looks like 360 is the
upper limit for $fn when inserting a DXF file.  I also tried various values
of $fs and $fa with similar results.
<http://forum.openscad.org/file/t1309/arcs.jpg>



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Re: Cant smooth this domed end

Ronaldo
In reply to this post by andy_at_blighty
Here are my notes:

1) I could not see the artifacts you have noticed with the rotate_extrude; the extrusion seems to be smooth; I am using OpenSCAD version 2018.01.06;

2) the render of the import polygon of end-dome.dxf (without extrusion) shows a series of concavities along the rounded part for $fn values greater than 150 as shown bellow:

end-dome-dxf.PNG

these artifacts are not present in the dxf when viewed with LibreCAD;

3) I could "fill" those concavities with a tricky code that makes the hull() of just that section of the polygon:

module endDome() import("end-dome.dxf", $fn=1000);

  difference(){
    hull() endDome();
    translate([0,-9.9]) square([2.7, 10]);
  }
  intersection() {
    endDome();
    translate([0,-9.9]) square([2.7, 10]);
  }

after that, I could generate a new dxf of a new polygon;

4) the render of the new dxf does not show any artifact.

My conclusion: there is something in your dxf file that is not digestible by OpenSCAD.

The trick I have used to "clean" end-dome.dxf may be applied to other files in a case by case basis but it is not neither general nor easy.

For your consideration I have attached the new dxf.



Em qui, 10 de jan de 2019 às 18:56, Andy Carlson <[hidden email]> escreveu:

Below is a very cut down sample of my model… which in reality is doing rotate_extrude on a DXF.

 

It creates a cylinder with a shallow dome on the end. The trouble is that I seem to be unable to smooth out the ‘tree rings’ on the end sufficiently.

 

If I reduce $fa to 0.5 then the end becomes coarser instead of smoother. I’ve also experimented with $fn and the end gets smoother up to a value of about 570 and then it gets worse. Messing with $fs doesn’t seem to help either.

 

Is there anything I can do to get past this problem?

 

$fs=.05;

$fa=.632;

 

rotate_extrude(convexity=10) {

    intersection() {

        circle(16.9);

        translate([-3,0,0]) {

            square([3,20]);

        }

    }

}

 

Regards,

Andy

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end-dome2.dxf (5K) Download Attachment
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Re: Cant smooth this domed end

andy_at_blighty

Thanks for your reply and effort on this.

 

While I would not rule out an issue specific to the DXF import or my DXF file in particular, I’ve completely eliminated that DXF from my full model and redrawn the dome using OpenSCAD primitives.

 

The ‘primitives’ version is nice and smooth when run on its own but when added back into the full model (and the dome DXF removed), the tree rings are still there.

 

I think you may be right about concavity. I suspected that the tree rings may involve the edges of some rings being indented but it’s difficult to be certain.

 

Regards, Andy

 

 

From: Discuss [mailto:[hidden email]] On Behalf Of Ronaldo Persiano
Sent: 12 January 2019 19:56
To: OpenSCAD general discussion <[hidden email]>
Subject: Re: [OpenSCAD] Cant smooth this domed end

 

Here are my notes:

 

1) I could not see the artifacts you have noticed with the rotate_extrude; the extrusion seems to be smooth; I am using OpenSCAD version 2018.01.06;

 

2) the render of the import polygon of end-dome.dxf (without extrusion) shows a series of concavities along the rounded part for $fn values greater than 150 as shown bellow:

 

end-dome-dxf.PNG

 

these artifacts are not present in the dxf when viewed with LibreCAD;

 

3) I could "fill" those concavities with a tricky code that makes the hull() of just that section of the polygon:

 

module endDome() import("end-dome.dxf", $fn=1000);

 

  difference(){

    hull() endDome();

    translate([0,-9.9]) square([2.7, 10]);

  }

  intersection() {

    endDome();

    translate([0,-9.9]) square([2.7, 10]);

  }

 

after that, I could generate a new dxf of a new polygon;

 

4) the render of the new dxf does not show any artifact.

 

My conclusion: there is something in your dxf file that is not digestible by OpenSCAD.

 

The trick I have used to "clean" end-dome.dxf may be applied to other files in a case by case basis but it is not neither general nor easy.

 

For your consideration I have attached the new dxf.

 

 

 

Em qui, 10 de jan de 2019 às 18:56, Andy Carlson <[hidden email]> escreveu:

Below is a very cut down sample of my model… which in reality is doing rotate_extrude on a DXF.

 

It creates a cylinder with a shallow dome on the end. The trouble is that I seem to be unable to smooth out the ‘tree rings’ on the end sufficiently.

 

If I reduce $fa to 0.5 then the end becomes coarser instead of smoother. I’ve also experimented with $fn and the end gets smoother up to a value of about 570 and then it gets worse. Messing with $fs doesn’t seem to help either.

 

Is there anything I can do to get past this problem?

 

$fs=.05;

$fa=.632;

 

rotate_extrude(convexity=10) {

    intersection() {

        circle(16.9);

        translate([-3,0,0]) {

            square([3,20]);

        }

    }

}

 

Regards,

Andy

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Re: Cant smooth this domed end

nophead
I think the DXF import draws arcs with the normal $fn, $fs, $fa settings but it then snaps it to a coarse grid, which is 1/1024. I don't think that is done anywhere else. The normal grid is 1024 times less than that. I.e. about nano metres instead of microns.

On Sat, 12 Jan 2019 at 20:11, Andy Carlson <[hidden email]> wrote:

Thanks for your reply and effort on this.

 

While I would not rule out an issue specific to the DXF import or my DXF file in particular, I’ve completely eliminated that DXF from my full model and redrawn the dome using OpenSCAD primitives.

 

The ‘primitives’ version is nice and smooth when run on its own but when added back into the full model (and the dome DXF removed), the tree rings are still there.

 

I think you may be right about concavity. I suspected that the tree rings may involve the edges of some rings being indented but it’s difficult to be certain.

 

Regards, Andy

 

 

From: Discuss [mailto:[hidden email]] On Behalf Of Ronaldo Persiano
Sent: 12 January 2019 19:56
To: OpenSCAD general discussion <[hidden email]>
Subject: Re: [OpenSCAD] Cant smooth this domed end

 

Here are my notes:

 

1) I could not see the artifacts you have noticed with the rotate_extrude; the extrusion seems to be smooth; I am using OpenSCAD version 2018.01.06;

 

2) the render of the import polygon of end-dome.dxf (without extrusion) shows a series of concavities along the rounded part for $fn values greater than 150 as shown bellow:

 

end-dome-dxf.PNG

 

these artifacts are not present in the dxf when viewed with LibreCAD;

 

3) I could "fill" those concavities with a tricky code that makes the hull() of just that section of the polygon:

 

module endDome() import("end-dome.dxf", $fn=1000);

 

  difference(){

    hull() endDome();

    translate([0,-9.9]) square([2.7, 10]);

  }

  intersection() {

    endDome();

    translate([0,-9.9]) square([2.7, 10]);

  }

 

after that, I could generate a new dxf of a new polygon;

 

4) the render of the new dxf does not show any artifact.

 

My conclusion: there is something in your dxf file that is not digestible by OpenSCAD.

 

The trick I have used to "clean" end-dome.dxf may be applied to other files in a case by case basis but it is not neither general nor easy.

 

For your consideration I have attached the new dxf.

 

 

 

Em qui, 10 de jan de 2019 às 18:56, Andy Carlson <[hidden email]> escreveu:

Below is a very cut down sample of my model… which in reality is doing rotate_extrude on a DXF.

 

It creates a cylinder with a shallow dome on the end. The trouble is that I seem to be unable to smooth out the ‘tree rings’ on the end sufficiently.

 

If I reduce $fa to 0.5 then the end becomes coarser instead of smoother. I’ve also experimented with $fn and the end gets smoother up to a value of about 570 and then it gets worse. Messing with $fs doesn’t seem to help either.

 

Is there anything I can do to get past this problem?

 

$fs=.05;

$fa=.632;

 

rotate_extrude(convexity=10) {

    intersection() {

        circle(16.9);

        translate([-3,0,0]) {

            square([3,20]);

        }

    }

}

 

Regards,

Andy

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Re: Cant smooth this domed end

andy_at_blighty
In reply to this post by andy_at_blighty

I managed to isolate the thing in my main model that makes the difference and causes the tree rings.

 

It uses $fn on the main barrel because I had found (with the 2015 stable version) that tuning $fa and $fs was not working beyond a point but $fn seemed to get around that problem. It uses the same $fn value for the rotate_extrude of the end dome.

 

So attached is a test model that produces tree rings with no DXF involvement. If you set BARRELFACETS to zero then you get a smooth end.

 

The issue is not quite the same as the one with my DXF test. With the DXF, the tree rings happen without $fn on the rotate_extrude and are of unequal size. In the latest test, they need the involvement of $fn and seem to be of equal size.

 

Too late for my print though – the STL went for print yesterday, so sanding down will be happening.

 

Regards, Andy


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