Dimension too large error

[crimestop]

I'm current using knots package v2.4 on texlive 2023. We compiling the following code

        \begin{tikzpicture}
        \begin{knot}[
            %draft mode=crossings,
            clip width=3,
        ]
            \strand (0,0)  --(2,2);
            \strand (0.5,0)  --(2.5,2);
        \end{knot}
    \end{tikzpicture}

the compiler(pdflatex) reports a "Dimension too large." error. However there's no error if we change (2.5,2) to (2.50001,2).

[crimestop]

Well, there seem still to be an error if we change (2.5,2) to (2.50001,2). However it's fine if we change (2.5,2) to (2.5001,2).

[loopspace]

This is an issue with the TikZ/pgf intersection routine. When intersecting two lined, it uses maths to work out the point (rather than a bounding box iteration that it uses for bézier curves). This allows for the possibility that the intersection point is not on the segments, so is a bit more general.

However, it means that it doesn't handle the case of parallel (or near parallel) lines well since that results in dividing by zero (or almost zero).

I presume that this example isn't your actual use case. There are a few work arounds depending on what you want to accomplish. One option is to replace one of the lines by a bézier curve that traverses the same line.

Another is simply to ignore the error since it only happens when the lines don't intersect.

[loopspace]

See, for example, https://github.com/pgf-tikz/pgf/issues/369