Module exact 

The exact half of the drawing pipeline.

The polygonal path draws what the mesh says: silhouettes are interior mesh edges whose triangles disagree about facing the eye, and visibility is occlusion sampling against the triangles. Both are as good as the chord, and no better.

This is the other half. A silhouette is where the surface’s own normal turns perpendicular to the view, which for the elementary surfaces is a curve with a closed form: a great circle on a sphere, a pair of rulings on a cylinder or a cone. Visibility is decided by asking the faces whether anything stands between a point and the eye: an exact curve/surface interference and a trim test, not a triangle count. What is still sampled is the drawing itself, because a drawing is polylines. The curves it samples and the classification it carries are exact.

A surface whose silhouette has no closed form (a torus, a spline) has it marched: the silhouette is one equation on the surface’s own chart, and the shared walker follows it. The curve drawn through the walk is held to the walk’s chord against the silhouette itself, between the walked points as well as at them.

Structs

Silhouette

One silhouette curve, and the face it belongs to.

Functions

iso_curves

The isoparametric curves of a face: u_count at constant u, v_count at constant v, each trimmed to the stretches that lie on the face.

project_exact

Project a shape into a drawing whose silhouettes and visibility are exact.

reflect_lines

The reflect lines of a shape under a light: where the surface turns away from the light rather than from the eye.

silhouettes

The exact silhouettes of a shape, seen along direction.