Ha ha! "It’s a maze of twisty little passages, all different."  Colossal
Cave Adventure!

On Mon, Feb 7, 2022 at 6:29 PM Bob Carlson bob@rjcarlson.com wrote:

We are all showing our age!

On 2/7/2022 7:44 PM, Leonard Martin Struttmann wrote:

If there is only one object (polyhedron or atomic object - cube/sphere/cylinder) then CGAL does not get called, it just makes a mesh, in your case a bad one, I'm guessing the blue represents the inside, as Adrian mentioned some inverted triangles.
With two objects CGAL gets called, sees the bad triangles and produces the error.

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Did you try enclosing it in render()?
On Feb 7, 2022, 18:01 -0800, Jordan Brown openscad@jordan.maileater.net, wrote:

On 2/7/2022 6:02 PM, Whosawhatsis wrote:

Does not help.

points = [ [0,0,0], [0,1,0], [1,0,0] ];
faces = [ [0,1,2] ];
render() polyhedron(points=points, faces=faces);

translate([5,5,5]) cube(1);

gives a CGAL error if the cube is included, and not if not.

Note that the "polyhedron" is malformed; it has only one face.

The union of the model with itself works but F6 will take a lot longer.

A better solution might be:

module model() {
points = [ [0,0,0], [0,1,0], [1,0,0] ];
faces = [ [0,1,2] ];
polyhedron(points=points, faces=faces);
}

module model2() sphere(10,$fn=100);

module check_model() {
difference() { // it doesn`t work when this is replaced by union()
children();
difference() {
cube(10,center=true);
cube(20,center=true);
}
}
}

check_model() model();
//check_model2() model();

However, that check will also take longer to render than the original model.

Em seg., 7 de fev. de 2022 às 23:17, Jordan Brown <
openscad@jordan.maileater.net> escreveu:

On 2/7/2022 7:48 PM, Ronaldo Persiano wrote:

Great!

The question is how much longer - and, if we're doing this inside
OpenSCAD itself, we could do it only when there's only one object to
process, which starts out as nearly zero time.

The result would definitely be slower than what we do now, but if it's a
negligible penalty on cases that are already really fast, the
understandability benefit is probably worth it.

It wouldn't be good if it was a noticeable slowdown but perhaps it only
needs a conversion from Polyset to Nef Polyhedron to find the error, rather
than an actual CSG op. I don't know how slow that is though.

On Tue, 8 Feb 2022 at 05:53, Jordan Brown openscad@jordan.maileater.net
wrote:

Did I get that right? Code below, screenshot attached, or here:
https://www.dropbox.com/s/t94m08knrv4tb97/Douglas.jpg?raw=1

difference()
{

//////////////////////////
// Customizable settings
//////////////////////////

// Diameter of the hole on the bottom (in mm).
HoleDiameter = 6;

// Depth of the hole in the bottom (in mm).  If you want the hole to go all the
way through then set this to a number larger than the total height of the
object.
HoleDepth = 10;

// If you want a D-shaped hole, set this to the thickness of the flat side (in
mm).  Larger values for the flat make the hole smaller.
HoleFlatThickness = 1.3;

// Height (in mm).  If dome cap is selected, it is not included in height.  The
shaft length is also not counted.
KnobHeight = 16;

// Diameter of base of round part of knob (in mm).  (Knurled ridges are not
included in this measurement.)
KnobDiameter = 28;

// Shape of top of knob.  "Recessed" type can be painted.
CapType = 0; // [0:Flat, 1:Recessed, 2:Dome]

// Do you want a large timer-knob style pointer?
TimerKnob=0; // [0:No, 1:Yes]

// Would you like a divot on the top to indicate direction?
Pointer1 = 0; // [0:No, 1:Yes]

// Would you like a line (pointer) on the front to indicate direction?
Pointer2 = 0; // [0:No, 1:Yes]

// Do you want finger ridges around the knob?
Knurled = 0; // [0:No, 1:Yes]

// 0 = A cylindrical knob, any other value will taper the knob.
TaperPercentage = 0; // [0:0%, 10:10%, 20:20%, 30:30%, 40:40%, 50:50%]

// Width of "dial" ring (in mm).  Set to zero if you don't want the ring.
RingWidth = 3;

// The number of markings on the dial.  Set to zero if you don't want markings.
(RingWidth must be non-zero.)
RingMarkings = 0;

// diameter of the hole for the setscrew (in mm).  If you don't need a hole, set
this to zero.
ScrewHoleDiameter = 0;

// Length of the shaft on the bottom of the knob (in mm).  If you don't want a
shaft, set this value to zero.
ShaftLength = 0;

// Diameter of the shaft on the bottom of the knob (in mm).  (ShaftLength must
be non-zero.)
ShaftDiameter = 10;

// Would you like a notch in the shaft?  It can be used for a press-on type knob
(rather than using a setscrew).  (ShaftLength must be non-zero.)
NotchedShaft = 1; // [0:No, 1:Yes]

//////////////////////////
//Advanced settings
//////////////////////////

RingThickness = 51;
DivotDepth = 1.51;
MarkingWidth = 1.51;
DistanceBetweenKnurls = 31;
TimerKnobConst = 1.8*1;

//////////////////////////
//Calculations
//////////////////////////

PI=3.141592651;
KnobMajorRadius = KnobDiameter/2;
KnobMinorRadius = KnobDiameter/2 * (1 - TaperPercentage/100);
KnobRadius = KnobMinorRadius + (KnobMajorRadius-KnobMinorRadius)/2;
KnobCircumference = PIKnobDiameter;
Knurls = round(KnobCircumference/DistanceBetweenKnurls);
Divot=CapType;

TaperAngle=asin(KnobHeight / (sqrt(pow(KnobHeight, 2) +
pow(KnobMajorRadius-KnobMinorRadius,2)))) - 90;

DivotRadius = KnobMinorRadius*.4;

union()
{
translate([0, 0, (ShaftLength==0)? 0 : ShaftLength-0.001])
difference()
{
union()
{
// Primary knob cylinder
cylinder(h=KnobHeight, r1=KnobMajorRadius, r2=KnobMinorRadius,
$fn=50);

if (Knurled)
	for (i=[0 : Knurls-1])
		rotate([0, 0, i * (360/Knurls)])
			translate([KnobRadius, 0, KnobHeight/2])
				rotate([0, TaperAngle, 0]) rotate([0, 0, 45])
					cube([2, 2, KnobHeight+.001], center=true);

if (RingMarkings>0)
	for (i=[0 : RingMarkings-1])
		rotate([0, 0, i * (360/RingMarkings)])
			translate([KnobMajorRadius + RingWidth/2, 0, 1])
				cube([RingWidth*.5, MarkingWidth, 2], center=true); 	
if (Pointer2==1)
	translate([KnobRadius, 0, KnobHeight/2-2])
		rotate([0, TaperAngle, 0])
			cube([8, 3, KnobHeight], center=true);		

if (RingWidth>0)
	translate([0, 0, RingThickness/2])
		cylinder(r1=KnobMajorRadius + RingWidth, r2=KnobMinorRadius,
				h=RingThickness, $fn=50, center=true);

if (Divot==2)
	translate([0, 0, KnobHeight])
		difference()
		{
			scale([1, 1, 0.5])
				sphere(r=KnobMinorRadius, $fn=50, center=true);

			translate([0, 0, 0-(KnobMinorRadius+.001)])
				cube([KnobMinorRadius*2.5, KnobMinorRadius*2.5,
						KnobMinorRadius*2], center=true);
		}

if (TimerKnob==1) intersection()
	{
		translate([0, 0, 0-(KnobDiameter*TimerKnobConst) + KnobHeight])
		sphere(r=KnobDiameter*TimerKnobConst, $fn=50, center=true);		

		translate([0-(KnobDiameter*TimerKnobConst)*0.1, 0,
				KnobHeight/2])
			scale([1, 0.5, 1])
				cylinder(h=KnobHeight, r=(KnobDiameter*TimerKnobConst)

•   					0.8, $fn=3, center=true);
    }
  

}

// Pointer1: Offset hemispherical divot
if (Pointer1==1)
translate([KnobMinorRadius*.55, 0, KnobHeight + DivotRadius*.6])
sphere(r=DivotRadius, $fn=40);

// Divot1: Centered cylynrical divot
if (Divot==1)
translate([0, 0, KnobHeight])
cylinder(h=DivotDepth*2, r=KnobMinorRadius-1.5, $fn=50,
center=true);

if (ShaftLength==0)
{
// Hole for shaft
translate([0, 0, HoleDepth/2 - 0.001])
difference()
{
cylinder(r=HoleDiameter/2, h=HoleDepth, $fn=20,
center=true);

		// Flat for D-shaped hole
		translate([(0-HoleDiameter)+HoleFlatThickness, 0, 0])
			cube([HoleDiameter, HoleDiameter, HoleDepth+.001],
					center=true);
	}

// Hole for setscrew
if (ScrewHoleDiameter>0)
	translate([0 - (KnobMajorRadius+RingWidth+1)/2, 0,
			HoleDepth/2])
		rotate([0, 90, 0])
		cylinder(h=(KnobMajorRadius+RingWidth+1),
				r=ScrewHoleDiameter/2, $fn=20, center=true);

}

// Make sure bottom ends at z=0
translate([0, 0, -10])
cube([(KnobMajorRadius+RingWidth) * 3,
(KnobMajorRadius+RingWidth) * 3, 20], center=true);
}

if (ShaftLength>0)
difference()
{
translate([0, 0, ShaftLength/2])
cylinder(h=ShaftLength, r=ShaftDiameter/2, $fn=20,
center=true);

	if (NotchedShaft==1)
	{
		cube([HoleDiameter/2, ShaftDiameter*2, ShaftLength],
				center=true);
	}

	// Hole for shaft
	translate([0, 0, HoleDepth/2 - 0.001])
		difference()
		{
			cylinder(r=HoleDiameter/2, h=HoleDepth, $fn=20,
					center=true);
	
			// Flat for D-shaped hole
			translate([(0-HoleDiameter)+HoleFlatThickness, 0, 0])
				cube([HoleDiameter, HoleDiameter, HoleDepth+.001],
						center=true);
		}
	
	// Hole for setscrew
	if (ScrewHoleDiameter>0)
		translate([0 - (KnobMajorRadius+RingWidth+1)/2, 0,
				HoleDepth/2])
			rotate([0, 90, 0])
			cylinder(h=(KnobMajorRadius+RingWidth+1),
					r=ScrewHoleDiameter/2, $fn=20, center=true);
}

}

rotate_extrude() polygon([[0,0],[0,8],[14,8],[17,0]]);
}

On Mon, 7 Feb 2022 10:25:40 -0500, you wrote: