Rotating a cylinder causes 3MF validation error

[hannobraun]

Rotating cylinders is possible as of #493. However, it produces an invalid 3MF file.

Here's the code of a model that displays the issue:

use std::{collections::HashMap, f64::consts::FRAC_PI_4};

use fj::syntax::*;

#[no_mangle]
pub extern "C" fn model(_: &HashMap<String, String>) -> fj::Shape {
    let cylinder = fj::Circle::from_radius(0.5)
        .sweep(1.0)
        .rotate([1., 1., 1.], FRAC_PI_4)
        .translate([4., 1., 1.]);

    cylinder.into()
}

And here's the error:

I wasn't able to see any obvious issues, so it must be something subtle. Probably a triangulation edge case, or possible it's related to the use of triangle representation for the cylinder side walls (#97).

[hannobraun]

I can still reproduce this, although the original code no longer compiles.

Here's the updated code:

use std::f64::consts::FRAC_PI_4;

use fj::{syntax::*, Angle};

#[fj::model]
pub fn model() -> fj::Shape {
    let cylinder = fj::Sketch::from_circle(fj::Circle::from_radius(0.5))
        .sweep([0., 0., 1.])
        .rotate([1., 1., 1.], Angle::from_rad(FRAC_PI_4))
        .translate([4., 1., 1.]);

    cylinder.into()
}

This trips our own validation code now:

thread 'main' panicked at 'Invalid approximation: Distinct points are too close (a: [3.5976310729378174, 0.7470603182991596, 1.1553086087630227], b: [3.5976310729378174, 0.7470603182991596, 1.1553086087630229], distance: 0.0000000000000002220446049250313)
source of `a`: Some(
    (
        Curve @ 0x55a996ea1820,
        [
            3.1415926535897936,
        ],
    ),
)
source of `b`: Some(
    (
        Curve @ 0x55a996ea1a30,
        [
            3.1415926535897936,
        ],
    ),
)
', /home/hanno/Projects/main/fornjot/crates/fj-kernel/src/algorithms/approx/face.rs:51:25
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

I've done some additional digging. This is the curve where a originates:

Curve {
    path: Line(
        Line {
            origin: [
                0.0,
                0.0,
            ],
            direction: [
                1.0,
                0.0,
            ],
        },
    ),
    surface: Surface @ 0x557f15d2bee0,
    global_form: GlobalCurve @ 0x557f15d0ffa0,
}

And the curve where b originates:

Curve {
    path: Circle(
        Circle {
            center: [
                0.0,
                0.0,
            ],
            a: [
                0.5,
                0.0,
            ],
            b: [
                0.0,
                0.5,
            ],
        },
    ),
    surface: Surface @ 0x557f15d2c970,
    global_form: GlobalCurve @ 0x557f15d0ffb0,
}

They reference different GlobalCurves, so this is probably just an object duplication issue. If so, this might be an instance of #1162.