[pstricks] Normal arrows along a curve

[Michael Sharpe]

On Jul 27, 2010, at 7:44 AM, James wrote:

> Hi,
> 
> I am new to PS Tricks, I am trying to draw a (pretty) Neumann boundary condition for a problem. What I need is the ability to place outward normal vectors along a path. So given a curve, you could draw it with a solid line or a dotted line - what I would like is to draw the line solid, but in the places where it would have been dotted, to have an small outward line with arrow. (or just a slightly smaller point size line)
> 
> How difficult is this? I bring up the similarity to a dotted line, because if it could be implemented at the "line" level, then you could easily draw lines with outward normal arrows using bezier curves, or really anything.
> 
> Thanks for any help,
> 
> James

Check out the section "Ticks and other marks along a curve" in the newest pstricks-add. With any curve, by defining a metric along the curve (eg, arc-length), you can arrange to draw any kind of mark, at intervals governed by that metric. The tangent and normal vectors are defined at each point so that would appear to give you what you need.

Michael