Not really a tutorial.

In LibreCAD, there's a drawing method to create an inscribed ellipse of a generic quadrilateral. The algorithm is based on:

A quadrilateral is a perspective of a square;

Finding the inscribed circle of a square is trivial;

The perspective of this circle gives the inscribed ellipse of the quadrilateral;

so the ellipse is found from the perspective of a circle.

My goal is to implement a way to allow specifying a perspective transform from GUI, and transform any selected entities (point, line, circle, ellipse, parabolas, splinepoints, cubic splines(need to verify the math)) to their perspective projection.

Angelos58 wrote

Thank you very much for link.

A lot of interesting issues.

Is there also tutorial for wrapping perspective a shape? For example a circle.