I have a curved path I imported into Illustrator, and I'd like to draw a line perpendicular to the curve at a particular point. I've searched google and this forum, but can't find any description of how to do it. Corel Draw has a button that lets you do this, so I'm hoping something similar exists in Illustrator...
i'm currently just calculating the angle at the point I want using the derivative, finding the angle, and then adding 90 degrees to it. But I need the line to be placed at a particular point, and the X/Y properties of the line are based on the ruler which isn't even in the center of the document (I want to position it relative to the artboard). As in, I just want to set the position of one endpoint of the line...
Bit of a pain, but here goes:
RIdiculous, isn't it? Welcome to Illustrator.
For a single instance of constructing a perpendicular to a curve, you can streamline the above suggestions a bit by:
SmartGuides on. (SmartGuides is the only reasonably reliable snapping function in Illustrator.)
1. Select the curved path. Copy.
2. Add Anchor Point Tool (the 'plusPen'): Click the curved segment where you want the point of tangency. Do not deselect the path.
3. LineTool: Mousedown on one of the Direction Lines ('curve handles') of the added Anchor Point (SmartGuides snap to) and drag to the AnchorPoint (SmartGuides snap to).
4. DoubleClick the Rotate Tool and rotate 90° (or click the end of the Line [at the tangency anchorPoint] with the Rotate Tool to set the center of transformation there, and then shiftDrag the opposite endPoint ).
5. If you don't want the added anchorPoint when you're done, delete the original curved path and then Paste In Front.
But for your fill pattern, you should build yourself a Pattern Swatch or a Brush, so you don't have to draw each perpendicular manually.