How to Continue Curved Lines in the Same Direction to Fill a Shape?

Question

Hi everyone!I'm working on a design where I need to continue a series of curved lines in the same direction to fill a shape evenly. The lines follow a smooth, wave-like pattern and I want to maintain consistent spacing and curvature as I extend them.My main challenge is figuring out the correct angle or curvature for each new line so the pattern stays visually consistent. Is there a way to measure or replicate the angle of existing curved lines in Illustrator? Or a technique/tool that helps automate this?Thank you!

Jacob Bugge · Answer

Letícia,

I would suggest your starting over and creating a new Blend for ease and accuracy/possible improvements, as described and shown below, with the Pem Tool, the Direct Selection Tool, and the Line Segment Tool, and if needed also Smart Guides being your friends, telling when you are within snapping distance, see links at the bottom. Most likely, this corresponds to the way the original artwork was made.

You can lock the current set as the basis and work on top of that, or start completely over, in either case starting with an extended version of the longest curve to the left:

1) Starting at the lower left beside and beneath the corner of the shape, create a new curve to the left with a height greater than the intended shape to fill and fully to the left of the shape, using the Pen Tool with just two end Anchor Points, ClickDragging both with the long Handle at the lower one, then adjusting the positions and Handles with the Direct Selection Tool, either to fit the direction and curving of one (or more) of the original curves, or improve the curve by comparing with the original ones;

2) Using the Line Segment Tool, create a corresponding straight line to the right with the same height, either with the same direction as the original short ones to the right or with the same direction as the bottom of the new curved path to the left to create paths that are parallel at the bottom;

2A) In the former case ClickDrag from the lower end of the short one to the right so the new line covers it, then with the bottom left Reference Point ticked in the Transform palette, set the value of H to the same as for the curved path from 1), then hold Ctrl/Cmd and press Enter to scale it up to fit as the full line, then align the full line with the curve from 1), usign the Transform palette or the Align palette;

2B) In the latter case, ClickDrag from the lower end of the new curved path from 1) so the new line follows the direction at the lower end, then adjust the full length in the same way as in 2A), then align vertically and move the line horizontally to be to the right of the shape;

It is possible to ensure that the new line follow the direction of the lower end the first path accurately by using the Handle in a few intermediate steps which can be described if needed;

Now you have the basis for the Blend:

3) Create the Blend with:

3A) Object>Blend>Options, setting Spacing to Specified Steps with a number one less than the desired number of intervals, and Orientation to Align to Path,

3B) Object>Blend>Make;

3C) Use Undo to go back and adjust if needed;

Now you have the curved (to straight) paths as a Blend, and the appearance extends past the shape on all sides;

You can use (a copy of) the shape as a Clipping Mask to only show the parts of the curves within it.

You can also Object>Blend>Expand if you wish to have actual paths; remember to keep a backup of the Blend.

Here is a set of sample drawings showing the steps, using step 2B) to have the straight line to the right with the same direction as the bottom of the curved path to the left:

Click to get closer, Click again to get closer still

You can look at Use Smart Guides, and specifically Set Smart Guides preferences here,

https://helpx.adobe.com/illustrator/using/rulers-grids-guides-crop-marks.html

For the Line Segment Tool, see the Advanced Toolbar and instructions in the links below,

https://helpx.adobe.com/illustrator/using/tools.html

https://helpx.adobe.com/illustrator/using/drawing-simple-lines-shapes.html