OGC validity of intersection touching shapes

[plooney]

Summary

For two touching rectangles with OGC validity on the intersection would be the touching edge

Steps to reproduce

use i_overlay::core::fill_rule::FillRule;
use i_overlay::core::overlay_rule::OverlayRule;
use i_overlay::float::overlay::{FloatOverlay, OverlayOptions};

fn main() {
    let subj = vec![vec![[1.0, 0.0], [0.0, 0.0], [0.0, 1.0], [1.0, 1.0]]];
    let clip = vec![vec![[2.0, 0.0], [1.0, 0.0], [1.0, 1.0], [2.0, 1.0]]];

    let options = OverlayOptions::<f64>::ocg();
    let mut overlay =
        FloatOverlay::with_subj_and_clip_custom(&subj, &clip, options, Default::default());
    let result = overlay.overlay(OverlayRule::Intersect, FillRule::EvenOdd);
    println!("{:?}", result.to_vec());
}

Expected behavior

Return a line where they touch

Actual behavior

returns empty list

Environment

• iOverlay version: 4.2.2
• Rust version: 2024
• OS: Max Tahoe 26.2

Additional context

[NailxSharipov]

Hello, thank you for this comment.

Currently this is a normal behavior since this library operates only on polygonal areas represented by closed contours.

However, the required information exists at the overlay graph level and can be extracted.
For this specific intersection operation, we also must extract all edges that have the subject on one side and the clip on the opposite side.

But, supporting this would require rethinking and extending the existing API.