"The multiple polygons are sharing an edge which is not manifold.

*Use rotate( (7.5-0.1)i ) which moves the second polygons face inside the
first polygons face."

Thanks, but I do not think that is the ultimate solution.  What if I wanted
the polygons to be separated and put

rotate( 10*i )

?  Then I'm back to the same problem.

Additional info:  When done individually, both board() and outerRing()
render fine.  It's only when I have both of them that the problem occurs.

On Tue, Aug 31, 2021 at 11:03 PM MichaelAtOz oz.at.michael@gmail.com
wrote:

When you have one object, you do not get a implicit union, so there is no conflict, try adding cube(1) or square(1) and you will see.

Fine. As long as they do not share a face/line.

Your original code had the right face of one polygon, identical to the left face of the next one. Either trust me that they can't coexist, or research 'nonmanifold'.

From: Leonard Martin Struttmann [mailto:lenstruttmann@gmail.com]
Sent: Wed, 1 Sep 2021 23:48
To: OpenSCAD general discussion
Subject: [OpenSCAD] Re: Module Disappears In Render

"The multiple polygons are sharing an edge which is not manifold.

Use rotate( (7.5-0.1)*i ) which moves the second polygons face inside the first polygons face."

Thanks, but I do not think that is the ultimate solution.  What if I wanted the polygons to be separated and put

rotate( 10*i )

?  Then I'm back to the same problem.

Additional info:  When done individually, both board() and outerRing() render fine.  It's only when I have both of them that the problem occurs.

On Tue, Aug 31, 2021 at 11:03 PM MichaelAtOz oz.at.michael@gmail.com wrote:

The multiple polygons are sharing an edge which is not manifold.

Use rotate( (7.5-0.1)*i ) which moves the second polygons face inside the first polygons face.

From: Leonard Martin Struttmann [mailto:lenstruttmann@gmail.com]
Sent: Wed, 1 Sep 2021 11:53
To: OpenSCAD general discussion
Subject: [OpenSCAD] Module Disappears In Render

Ok, this one has me stumped.  This is an excerpt from a larger model, I've simplified it as much as I can.

When I Preview, both modules, board() and outerRing(), are shown. [See attached]

When I Render, only board() is displayed. [See attached]

Obviously, I'm missing something simple here, but what?

Thanks!

Len

$fn = 48;

RPiHQcamera();

boardXYZ            = [ 38, 38, 1.4 ];
boardCornerR        = 2;
boardExtentZ        = boardXYZ.z;

outerRingPetalCount  = 48;
outerRingPetalWidth  = 360 / outerRingPetalCount;

outerRingOuterR      = 36/2;
outerRingInnerR      = 35.4/2;
outerRingPetalHeight = outerRingOuterR - outerRingInnerR;
outerRingZ          = 10.2;

p = [ [0,0], for (a=[-15:15]) let (
r = a/4,
theta = 90+(a * 180/15) )
[ (outerRingOuterR+outerRingPetalHeight*sin(theta))cos(r), (outerRingOuterR+outerRingPetalHeightsin(theta))*sin(r)] ];

module outerRing()
{
translate( [ 0, 0, boardExtentZ] )
linear_extrude( outerRingZ )
//  for ( i=[0:47] )
//  for ( i=[0:0] )
for ( i=[0:1] )
{
rotate( 7.5*i )
polygon( p );
}
}

module board()
{
linear_extrude( boardXYZ.z )
hull()
for (i=[-1:2:1], j=[-1:2:1] )
{
translate( [ i*(0.5boardXYZ.x-boardCornerR), j(0.5*boardXYZ.y-boardCornerR) ] )
circle( r=boardCornerR );
}
}

//******************************
module RPiHQcamera()
//******************************
{
board();
outerRing();
}
//******************************

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Thanks!  So, merely separating the polygons with rotate( 10*i ) did NOT
solve the problem, since all of the polygons started at [0,0].

Two solutions:

1. Move the center point ever so slightly:

p = [ [0.001,0], for (a=[-15:15]) let (
r = a/4,
theta = 90+(a * 180/15) )
[ (outerRingOuterR+outerRingPetalHeight*sin(theta))cos(r),
(outerRingOuterR+outerRingPetalHeightsin(theta))*sin(r)] ];

module outerRing()
{
translate( [ 0, 0, boardExtentZ] )
linear_extrude( outerRingZ, convexity=100 )
for ( i=[0:47] )
{
rotate( 7.5*i )
polygon( p );
}
}

2. Just make one polygon:

p = [ for (a=[-1804:1804]) let (
r = a/4,
theta = 90+(a * 180/15) )
[ (outerRingOuterR+outerRingPetalHeight*sin(theta))cos(r),
(outerRingOuterR+outerRingPetalHeightsin(theta))*sin(r)] ];

module outerRing()
{
translate( [ 0, 0, boardExtentZ] )
linear_extrude( outerRingZ, convexity=100 )
polygon( p );
}

My only questions, then, are: Why did outerRing(), by itself, render
successfully and produce an STL that Cura is happy with?  That is, why did
the problem only occur when another module is introduced?  Also, why are
there no warnings or errors?

On Wed, Sep 1, 2021 at 9:12 AM MichaelAtOz oz.at.michael@gmail.com wrote:

On 9/1/2021 8:18 AM, Leonard Martin Struttmann wrote:

CGAL is what really dislikes objects that aren't perfectly formed, and
doesn't get involved unless there's more than one object.

In 2021.01 I get:

Parsing design (AST generation)...
Saved backup file:
C:/Users/Jordan/Documents/OpenSCAD/backups/unsaved-backup-QApaZXoi.scad
Compiling design (CSG Tree generation)...
Rendering Polygon Mesh using CGAL...
ERROR: The given mesh is not closed! Unable to convert to
CGAL_Nef_Polyhedron.
Geometries in cache: 19
Geometry cache size in bytes: 1412968
CGAL Polyhedrons in cache: 1
[...]

But I don't get the error when I F6 again.  I assume that either the bad
result has been cached, or the "suppress duplicate error reports" stuff
is getting involved.

I have one suggestion and a pointless rant:

Suggestion:  caching the results of renders that encountered errors is
probably bad.

Pointless rant:  CGL is too darned picky about its polyhedra.

Wow!  Yes, just that single error the first time.

Thanks, everyone!

On Wed, Sep 1, 2021 at 11:20 AM Jordan Brown openscad@jordan.maileater.net
wrote:

Yes, as that node was evaluated (and got an error) the node was then cached, so subsequent F6 don't get evaluated again, so no error.

If you think something is strange, it is always worth doing Design/Flush-cache.

Sharing a point (2D) is also non-manifold, as is sharing a single edge (3D).

The rule of thumb with multiple objects, either clearly separated or embed part of one within the other, don't just park them touching side to side.

From: Leonard Martin Struttmann [mailto:lenstruttmann@gmail.com]
Sent: Thu, 2 Sep 2021 05:45
To: OpenSCAD general discussion
Subject: [OpenSCAD] Re: Module Disappears In Render

Wow!  Yes, just that single error the first time.

Thanks, everyone!

On Wed, Sep 1, 2021 at 11:20 AM Jordan Brown openscad@jordan.maileater.net wrote:

On 9/1/2021 8:18 AM, Leonard Martin Struttmann wrote:

My only questions, then, are: Why did outerRing(), by itself, render successfully and produce an STL that Cura is happy with?  That is, why did the problem only occur when another module is introduced?

CGAL is what really dislikes objects that aren't perfectly formed, and doesn't get involved unless there's more than one object.

Also, why are there no warnings or errors?

In 2021.01 I get:

Parsing design (AST generation)...
Saved backup file: C:/Users/Jordan/Documents/OpenSCAD/backups/unsaved-backup-QApaZXoi.scad
Compiling design (CSG Tree generation)...
Rendering Polygon Mesh using CGAL...
ERROR: The given mesh is not closed! Unable to convert to CGAL_Nef_Polyhedron.
Geometries in cache: 19
Geometry cache size in bytes: 1412968
CGAL Polyhedrons in cache: 1
[...]

But I don't get the error when I F6 again.  I assume that either the bad result has been cached, or the "suppress duplicate error reports" stuff is getting involved.

I have one suggestion and a pointless rant:

Suggestion:  caching the results of renders that encountered errors is probably bad.

Pointless rant:  CGL is too darned picky about its polyhedra.

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"The rule of thumb with multiple objects, either clearly separated or
embed part of one within the other, don't just park them touching side to
side."

MichaelAtOz, this statement confuses me.  I stack objects, face-to-face,
vertically and horizontally all the time with no problems.  Have I just
been lucky up until now? Or, is there a specific context that I'm missing?

On Wed, Sep 1, 2021 at 5:42 PM MichaelAtOz oz.at.michael@gmail.com wrote:

You have probably been lucky. For example if you stack integer sized cubes
face to face CGAL can union them but if you stack 0.1mm cubes it will
likely fail because 0.1 cannot be represented exactly in floating point.

On Thu, 2 Sept 2021 at 18:55, Leonard Martin Struttmann <
lenstruttmann@gmail.com> wrote: