Function fillet_extruded_profile

pub fn fillet_extruded_profile(
    profile: &Profile,
    direction: Vec3,
    depth: Scalar,
    edge: EdgeSelector,
    size: FeatureSize,
    tolerance: Tolerance,
) -> GeomResult<ExactBRep>

Fillet one vertical edge of an exact extruded rectangle.

The blend is a real cylindrical face, not a many-segment approximation. A vertical edge of a +z prism sweeps its cross-section unchanged, so the blend surface is Surface::Cylinder with its axis parallel to z, stitched between the two planar walls it is tangent to.

Tangency is constructed, not asserted

The blend axis sits on the internal angle bisector at distance r / sin(theta/2) from the corner, where theta is the interior angle. At that distance the perpendicular from the axis to each adjacent wall is exactly r, so the cylinder meets both walls tangentially by construction. For the right angle of a rectangle this is r * sqrt(2). Nothing is checked afterwards, so nothing can drift.

Errors

Refuses a radius that reaches past either neighbouring corner, and the same input families the chamfer refuses.