roof(method="straight") fails with complex outlines

[MethylBromide]

Describe the bug WARNING: PolySet -> Manifold conversion failed: NotManifold Trying to repair and reconstruct mesh.. ERROR: [manifold] Input mesh is not closed! ERROR: [manifold] Surface_mesh -> Manifold conversion failed: NotManifold

-- and no object is created.

To Reproduce Steps to reproduce the behavior:

1. Enable the roof function in your preferences.
2. Execute the script below. This displays the word "plugh" with a 45° slope to its sides. So far, so good.
3. Now check the growtext checkbox in Customizer. This results in the error shown above, and no object is created.
4. Use customizer to change method to "voronoi" rather than "straight". This avoids the error and gives the intended output.
5. Use customizer to change method back to "straight", which causes the problem to recur (though the console error isn't always shown).
6. Now in Customizer, set $fa = 4. This avoids the error and gives the intended output.

Expected behavior I would hope roof would work with no error even if the polygon segments are small.

Code reproducing the issue

growtext = false;
$fa = 1;
$fs = 0.1;

module chamfer(height=2, angle=45, method="straight", size = 1000, embiggen = false) {
    a = min(abs(angle),89);
    render()
    difference() {
        union() {
            scale([1,1,sin(45)/sin(a)])
            roof(method)
            offset(delta=embiggen ? height : 0, chamfer=true)
            children();
        }
        translate([-size/2, -size/2, height]) cube([size, size, size]);
    }
}

chamfer(.3, embiggen = growtext) text("plugh",  size=10, halign="center", valign="center");

Screenshots n/a

Environment and Version info (please complete the following information):

• OS: [e.g. Windows 10, macOS 12 Monterey, Ubuntu 22.04]
• System: [e.g. Intel PC 64-bit, Raspberry PI 4]
• OpenSCAD Version [e.g. 2021.01, 2023.04.16] and where it was installed from

Library & Graphics card information If applicable, add the content of the Help->Library Info window, or the output of running the openscad --info command.

Additional context I'm not certain the problem is entirely with "roof" -- it might be "offset" is producing some nonsensical output which might contribute to the problem. But either way I'd like this sample code to work.

[UBaer21]

version 2024.8.30 renders this without error

But the cube size has some severe impact on the result - using bigger cubes to cut will lower the precision and causing strange artifacts. here with size=20000

[MethylBromide]

I am using the same version as you. Sorry I didn't say the version. The "working" picture you posted is of the situation I already know works -- where we don't enlarge the text before roofing it. The error occurs when you check the "growtext" box, which results in using roof on the output of offset (with delta > 0), which is supposed to look like this: Notice how the letters are thicker than in your screenshot.

[thehans]

But the cube size has some severe impact on the result - using bigger cubes to cut will lower the precision and causing strange artifacts. here with size=20000

Looks like another case of https://github.com/openscad/openscad/issues/4871