A spline stored by fit points (DWG R2013+ scenario 2) has no control points
or knots, so the renderer — which built its curve from control points —
produced nothing and the spline was invisible. When a spline has fewer than
two control points but at least two fit points, interpolate a smooth
Catmull-Rom curve through the fit points and emit it as a dense polyline.
Open ends use reflected phantom points; closed/periodic splines wrap.
Pairs with the acadrust bump (e8e422a) that decodes the R2013+ fit-point
scenario correctly — together they make the fit-point spline in
Annotation-2D-Mesh-Solid-BIM.dwg render.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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