# Tracing logic behind the pen tool / bezier curve

One of the strategies I employ when using the Pen Tool in Illustrator to trace something is to use as few nodes as possible to make the curves as smooth as possible. I'm often surprised by what curve variations can be managed between a mere two nodes, and on the other hand occasional come across seemingly simply curve segments that require three or more nodes to trace properly. As a somewhat scientifically minded person, I find myself wanting to "know" just what's going on...

I wondering whether any experienced tracers out there have a kind of mental checklist for when they need to drop another node, or whether anyone has a good summary of it from a maths point of view?

• I'm having similiar problems, and I've coded a Bezier tool in OpenGL years ago :) Maybe I should revisit it. I'm working mostly in Inkscape but the problems are the same. I wonder if a similar "rule" would be to initially place an anchor point every where the curve of the line changes direction. I'll have to practice to find out. Let me know if that helps. Nov 14, 2016 at 20:56

I've just been reading good blog post that touches on this: http://philippaberrysmith.wordpress.com/2011/08/23/advanced-pen-tool-illustrator/

It's worth a read but here are a couple highlights:

• Work in one direction (i.e clockwise OR anti-clockwise) don’t change directions mid-drawing.
• Keep the handles of your curves pointing in the direction you are drawing. If they point backwards, you will get nasty (or perhaps useful) bumps and squiggles.
• It is usually best to use a semi-transparent colour to trace with, rather than a line. The thickness of the line can obscure the actual path.
• Aim to create as few points as necessary.
• Make extrema points to start with. They are a good place to start, before you get a feel for where the “next point” should go. Extrema points are those points situated on the horizontal or vertical flatness of a curve. Use the Shift key to ensure accurate 90° lines.