Hi,

I'm trying to create a teardrop shape using OpenSCAD - however I'm getting
issues with the rendering. It is only giving me a semicircle, yet in preview
it looks exactly how I want it to.

I have tried to translate the triangular portion so that it is inside the
semicircle, however this didn't seem to help.

Thanks,
Ed

radius = 15;
height = 10;
length = 50;

union () {
difference() {
cylinder(h=height,r=radius,center=false,$fn = 100);
translate([-radius,0,0])//translate so centered
cube(size=[radius2, radius2, height], center=false, $fn = 100);
//have so semicircle, slightly larger
}
//translate([0,-0.5,0])
polyhedron( //triangle
points = [
[-radius,0,0],[radius,0,0],[0,length,0], //bottom
[-radius,0,height],[radius,0,height],[0,length,height] //top
],
faces = [
[3,4,5],[0,1,2], //top and bottom
[0,3,5],[0,5,2], // -x to y
[0,4,3],[0,4,1], // -x to x
[1,4,2],[4,5,2] // x to y
], $fn = 100
);
}

--
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Check View/Thrown-together (after F5 - maybe need to Design/Flush-cache) the
purple shows your polyhedron is inside out.

Unless specifically shown otherwise above, my contribution is in the Public Domain; To the extent possible under law, I have waived all copyright and related or neighbouring rights to this work. This work is published globally via the internet. :) Inclusion of works of previous authors is not included in the above.

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View this message in context: http://forum.openscad.org/Issue-between-preview-and-rendering-tp13555p13557.html
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You also want to difference() something slightly bigger than the first object
otherwise the preview looks bad (https://en.wikipedia.org/wiki/Z-fighting),
like so

s=0.01;

union () {
difference() {
cylinder(h=height,r=radius,center=false,$fn = 100);
translate([-radius,0,-s])//translate so centered
cube(size=[radius2, radius2, height+s*2], center=false, $fn =
100); //have so semicircle, slightly larger
}

...

Unless specifically shown otherwise above, my contribution is in the Public Domain; To the extent possible under law, I have waived all copyright and related or neighbouring rights to this work. This work is published globally via the internet. :) Inclusion of works of previous authors is not included in the above.

The TPP is no simple “trade agreement.”  Fight it! http://www.ourfairdeal.org/

View this message in context: http://forum.openscad.org/Issue-between-preview-and-rendering-tp13555p13558.html
Sent from the OpenSCAD mailing list archive at Nabble.com.

If the model should stay as a flat object, it might be helpful to create
the shape in 2D and just extrude that at the end. In most cases that's
much faster then directly going to 3D and has no risk of producing
problematic geometry.

radius = 15;
height = 10;
length = 50;

linear_extrude(height = height) {
hull() {
circle(r = radius);
translate([0, length]) circle(r = 0.1);
}
}