11b) Drawing "Automatic" Pattern Repeats (Part 2)

In the previous post, I talked about how to move an object's center of rotation to create "automatic" pattern repeats. I used very basic examples (a ring and a trefoil) and did not build up the diagram any further. In order to build up the diagram, we need to use a feature in Inkscape called guides. If you are unfamiliar with guides, click here to read more. 

The reason we will be using guides is so that we can match up the center of rotation of the rings, chains, and picots in our diagram. We will be using the intersection of a horizontal and a vertical guide as a "snapping point" for all of our rotation centers. This will ensure that each element rotates around the same central axis.

Before I begin, be sure to familiarize yourself with the hotkeys on the right side of the screen (these will appear after you have dragged at least one guide onto the screen). The topmost button is responsible for turning guide snapping on and off:

A bit further down is a button to "snap other points":

Just below "snap other points" is another button with crosshairs, which enables an object's center of rotation to be snapped to guides:

For the purpose of this tutorial, you will need to enable the above features (the buttons will be a darker shade of gray when selected). As you work on building your diagram, keep in mind that it is also okay to turn guide snapping off when you don't need it. It can sometimes get in the way when trying to place parts of a drawing. I regularly toggle between turning snapping on and off by pressing the first button mentioned above.

Now that you have familiarized yourself with guides, it's time to start with an example. I'm going to use a trefoil like I did in my previous post:

This time, however, I am also going to add one horizontal and one vertical guide to create an intersection. As I drag my trefoil over the vertical guide, it will snap into place, centering itself over the line:

Just as I did with the examples in my previous post, I am going to relocate the trefoil's center of rotation by dragging the crosshairs along the screen. This time, I'm going to drag them to the guide intersection and let them snap into place:

I can duplicate my trefoil (CTRL+D) and rotate each duplication by 90 degrees to get the following:

Notice how all of the trefoils rotate around the guide intersection. To build upon this diagram, I am going to add some chains. Using the Bezier tool, I've drawn a chain between two of my trefoils. I've relocated the chain's center of rotation to the guide intersection as well:

Now the chain will be rotating around the same central axis as the trefoil. Duplicating the chain and rotating each duplication by 90 degrees connects all of the trefoils together:

Are you beginning to see how this is a useful tool for diagramming? You don't have to worry about placing each piece by hand. You can let the computer do the work for you.

Sometimes, we can use horizontal and vertical flips to place parts of a diagram. Say I want to draw a couple of picots, one on each side of the large ring in the trefoil. I can begin by drawing one picot (shown in blue for contrast):

Now I can click on the picot a second time, grab its rotation crosshairs, and snap them to my vertical guide:

Duplicating the picot and performing a horizontal flip will place another picot on the opposite side of the ring:

Let's take this one step further and group these two picots together (CTRL+G), so that they can be rotated around the diagram. After grouping the picots, I clicked on them once more to grab the rotation crosshairs, and snapped the crosshairs to the guide intersection.

Duplicating and rotating each picot group by 90 degrees places picots all around the diagram:

These techniques can be applied quite liberally to many different types of diagrams. Let your imagination and situation guide you, and don't be afraid to experiment with new possibilities!

A Sample Drawing

There is one last trick that I like to combine with everything mentioned above: Importing a photo and drawing on top of it. A photo is a good reference for where to place each element, and leaves guess work to a minimum. If you'd like to know more about importing photos and using layers, read through Part 10 of my Inkscape tutorial series by clicking here.

To give you an idea of how I put everything together, I'm going to provide some in progress photos of drawing a diagram. For the following example, I'm using a piece of tatting scrap that I found in one of my plastic bags.

First, I took a scan of the tatting and saved it to my computer:

Next, I imported the photo into Inkscape and resized it to fit on the page (be sure to hold the CTRL key down when resizing to maintain proportions). The photo might need to be rotated slightly to make sure that everything is lined up as straight as possible.

I reduced the opacity of the image to 75% so that it won't obstruct my ability to see rings, chains, and picots drawn on top of it. I renamed the current layer "Photo" and locked the layer down to prevent accidentally moving it.

Lastly, I dragged a few guides and placed them as accurately as possible over the drawing, creating a central intersecting point. This finishes the set up phase.

For the drawing phase, I added a new layer named "Diagram" on top of the Photo layer. I started by drawing one small ring and one large ring on the Diagram layer. I used a combination of duplication, rotation, and guide snapping to automatically place copies of my rings:

In my experience, it is wise to draw a few rings before drawing any chains. This way, you can see where to start and end your chains. After the central rings were drawn, I used the Bezier tool to draw a chain. All other chains were automatically placed with duplication, one horizontal flip, and some 90 degree rotations:

I used similar techniques to add the outer rings:

And the picots:

As you can see, I like to build my diagrams one element at a time. I find that this method works well for me, although you might find that other methods work better for you.

To make everything cohesive, I selected my entire diagram and grouped it together. I changed the stroke value to 1.5 pixels so that all of my lines are uniform.

If you'd like to see your diagram unobstructed by the photo, you can hide the photo layer. Just click on the eyeball icon on the bottom left of the screen, right near your layer name (make sure you are on the photo layer first). Here is my finished diagram:

That's it for this section of the tutorial. I hope that the information presented in these past few posts doesn't seem too daunting. This is my favorite technique to use with Inkscape, and it saves a lot of time when drawing diagrams. I promise, it gets much easier with practice. If you have any questions, don't hesitate to ask!