How do I keep edged flush when tracing with the pen tool in Illustrator?

Question

I'm just learning how to trace images with the pen tool in Illustrator -how do you trace when you have lines protruding from the whole (a line that offshoots) or when you have two objects which need to be flush with each other?

Is there a strategy for tracing a complex image with different shapes, such as a person wearing shirt?

For example, something like this:

Answer 1

Let's say we have 2 shapes as on your picture (face + head).

I make these two shapes overlapping with the face layer below the "head":

I duplicate the head layer, Select 1 head and face layers and by Pathfinder operation Minus Back get this perfect match -

Next:

Let's say you should create long ray as you asked. I choose on Direct Selection Tool (A) and click on the anchor point as in the picture:

Next, I press right arrow to move the anchor point to the desired location:

This is the result:

You can correct the curve operating handles of this anchor point.

Next, I thicken the stroke and expand - the picture will be perfect.

Answer 2

Smart guides (ctrl-u / cmd-u) can help, but they aren't always enough, especially on curves.

Often it's best to overlapping path lines - if it's solid fill it might be better to just go underneath, and if it's empty outlines it might be better to just stop when you connect the line (like you would if drawing on paper: you wouldn't carefully draw over the line you've already drawn).

For when you do need overlapping lines and smart guides aren't enough, here's one way I know of. It's a little bit fiddly but works.

To summarize:

• select the points where you want perfect overlap using the direct selection tool (white arrow, A) or lasso (Q),
• copy and paste in the same location with ctrl-C ctrl-F (cmd instead of ctrl on Mac),
• draw the rest of the path joining that new path.

Tip: Draw your new line very close to the duplicated path, then join, else you might distort the duplicate (this'll make sense when you try it).