I've been working with the sweep and have run into a problem.

The base shape is the intersection of two circles with the same radius with a hole in the middle.  It looks like an eye with a width of 20 and height of 10.  It is a valid region.

When I sweep that shape, it fails.  Intersecting that shape with a rectangle with width = 19.990, it works.  A width of the cut box greater than 19.990 fails.  Taking out the hole works even with no cut.

Test case below

The preview shows the shape used by sweep and the intersection of the circles with the cut box.

The error generated by having the hole and increasing the width of the cut box to >= 19.991 or removing it results in:

ERROR: Assertion 'is_path(points, dim = undef, fast = true)' failed: "Input to path3d is not a path" in file ../.local/share/OpenSCAD/libraries/BOSL2/coords.scad, line 73

TRACE: called by 'path3d' in file ../.local/share/OpenSCAD/libraries/BOSL2/vnf.scad, line 510

TRACE: called by 'vnf_from_region' in file ../.local/share/OpenSCAD/libraries/BOSL2/skin.scad, line 1402

TRACE: called by 'sweep' in file ../.local/share/OpenSCAD/libraries/BOSL2/skin.scad, line 1416

TRACE: called by 'sweep' in file testchord5.scad, line 62

TRACE: called by 'if' in file testchord5.scad, line 62

TRACE: called by 'if' in file testchord5.scad, line 46

It works if you remove the hole no matter what the cut box is set to.

include <BOSL2/std.scad> $fn = 96; // height maxZ = 60; // width of circle intersection chord = 20; // height of circle intersection sag2 = 10; // width of cut shape cut = 19.990; // do the sweep doSweep = true; // do center hole doHole = true; // do chop doCut = true; module dummy(){} function r_sag_chord(sag,chord) = sag/2 + chord^2 / (8sag); rintersect = r_sag_chord(sag2/2,chord); // radii of the circles dy = rintersect-sag2/2; // displacement of intersecting circles echo("\nInput parameters", chord=chord, sag2=sag2, cut=cut); echo("control switches ", doCut=doCut, doHole=doHole, doSweep=doSweep); echo(str("calculated values radius=",rintersect," center shift=",dy)); scaleX = [ 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8]; scaleY = [ 1.0, 0.9, 0.8, 0.7, 0.65, 0.63, 0.6, 0.55, 0.5]; levels = len(scaleX)-1; a = [for (i=[0:levels]) up(imaxZ/levels)xscale(scaleX[i]) yscale(scaleY[i])]; shape1 = move([0,dy,0], p=circle(r=rintersect)); shape2 = move([0,-dy,0], p=circle(r=rintersect)); shapei = intersection(shape1,shape2); // interection of the circles shapecut= rect([cut, sag2+1]); // cut box shapeic = intersection(shapei, shapecut); // intersection cut off shape = (doCut)? (doHole)? difference(shapeic, circle(d=4)) // shape with hole and cut : shapeic // shape cut with no hole : (doHole)? difference(shapei, circle(d=4)) // uncut shape with hole : shapei; // uncut shape with no hole if (is_valid_region(shape)) { echo("shape OK"); if($preview) { // show original shapes // outside shape with cut box in red translate([0,-20,0]) stroke(shapei, width=.1); if(doCut) color("red") { translate([0,-20,0]) stroke(shapecut, width=.1, closed=true); translate([chord/2+3,-20,0]) text("cut box",size=2); } translate([0,-30,0]) text("Intersection of circles", size=2, halign="center"); // bottom shape translate([0,-40,0]) stroke(shape, width=.1); translate([0,-50,0]) text("input to shape", size=2, halign="center"); } if(doSweep) sweep(shape, a); } else { echo("shape NG"); }

--
Bob

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This works:

//shape  = difference(shapei, circle(d=4));    // shape with hole
//
//if (is_valid_region(shapei)) {
//    echo("\n\nshape is a valid region\n\n");
//    sweep(shapei, T);
//} else {
//    echo("shapei NG");
//}

difference()
{
sweep(shapei, T);
sweep(circle(d=4),T);
}

On Thu, Feb 24, 2022 at 2:50 PM Adrian Mariano avm4@cornell.edu wrote:

Can you post a non-mangled version of your code?  It's been
reformatted into a single line.

On Thu, Feb 24, 2022 at 11:11 AM Bob Ewart jinnicky@bobsown.net wrote:

I've been working with the sweep and have run into a problem.

The base shape is the intersection of two circles with the same radius with a hole in the middle.  It looks like an eye with a width of 20 and height of 10.  It is a valid region.

When I sweep that shape, it fails.  Intersecting that shape with a rectangle with width = 19.990, it works.  A width of the cut box greater than 19.990 fails.  Taking out the hole works even with no cut.

Test case below

The preview shows the shape used by sweep and the intersection of the circles with the cut box.

The error generated by having the hole and increasing the width of the cut box to >= 19.991 or removing it results in:

ERROR: Assertion 'is_path(points, dim = undef, fast = true)' failed: "Input to path3d is not a path" in file ../.local/share/OpenSCAD/libraries/BOSL2/coords.scad, line 73

TRACE: called by 'path3d' in file ../.local/share/OpenSCAD/libraries/BOSL2/vnf.scad, line 510

TRACE: called by 'vnf_from_region' in file ../.local/share/OpenSCAD/libraries/BOSL2/skin.scad, line 1402

TRACE: called by 'sweep' in file ../.local/share/OpenSCAD/libraries/BOSL2/skin.scad, line 1416

TRACE: called by 'sweep' in file testchord5.scad, line 62

TRACE: called by 'if' in file testchord5.scad, line 62

TRACE: called by 'if' in file testchord5.scad, line 46

It works if you remove the hole no matter what the cut box is set to.

<code>

include <BOSL2/std.scad> $fn = 96; // height maxZ = 60; // width of circle intersection chord = 20; // height of circle intersection sag2 = 10; // width of cut shape cut = 19.990; // do the sweep doSweep = true; // do center hole doHole = true; // do chop doCut = true; module dummy(){} function r_sag_chord(sag,chord) = sag/2 + chord^2 / (8sag); rintersect = r_sag_chord(sag2/2,chord); // radii of the circles dy = rintersect-sag2/2; // displacement of intersecting circles echo("\nInput parameters", chord=chord, sag2=sag2, cut=cut); echo("control switches ", doCut=doCut, doHole=doHole, doSweep=doSweep); echo(str("calculated values radius=",rintersect," center shift=",dy)); scaleX = [ 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8]; scaleY = [ 1.0, 0.9, 0.8, 0.7, 0.65, 0.63, 0.6, 0.55, 0.5]; levels = len(scaleX)-1; a = [for (i=[0:levels]) up(imaxZ/levels)xscale(scaleX[i]) yscale(scaleY[i])]; shape1 = move([0,dy,0], p=circle(r=rintersect)); shape2 = move([0,-dy,0], p=circle(r=rintersec
t)); shapei = intersection(shape1,shape2); // interection of the circles shapecut= rect([cut, sag2+1]); // cut box shapeic = intersection(shapei, shapecut); // intersection cut off shape = (doCut)? (doHole)? difference(shapeic, circle(d=4)) // shape with hole and cut : shapeic // shape cut with no hole : (doHole)? difference(shapei, circle(d=4)) // uncut shape with hole : shapei; // uncut shape with no hole if (is_valid_region(shape)) { echo("shape OK"); if($preview) { // show original shapes // outside shape with cut box in red translate([0,-20,0]) stroke(shapei, width=.1); if(doCut) color("red") { translate([0,-20,0]) stroke(shapecut, width=.1, closed=true); translate([chord/2+3,-20,0]) text("cut box",size=2); } translate([0,-30,0]) text("Intersection of circles", size=2, halign="center"); // bottom shape translate([0,-40,0]) stroke(shape, width=.1); translate([0,-50,0]) text("input to shape", size=2, halign="center"); } if(doSweep) sweep(shape, a); } else { echo("shape NG"); }

</code>

--
Bob

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