Adobe Illustrator is a powerful vector program made for digital and print designers. Vector shapes are made to scale without any quality loss, which makes them quite different from pixel graphics. This means vector graphics can be manipulated differently and under different contexts which may be confusing for new designers.
In this post I'd like to cover a brief how-to process of vector manipulation in Adobe Illustrator. I'll explain the absolute basics of shape tools and how to manipulate them. Photoshop users who are familiar with vectors will recognize some of these terms. Others who are brand new to Illustrator will just need time to practice the fundamentals of this powerful design suite.
Shapes can be created in any Illustrator document using any resolution. The startup screen offers a number of presets so choose any of them, or create your own new document.
From here try dragging a rectangle onto the screen with the rectangle tool(shortcut M). You'll notice a blue box surrounds the rectangle when it's selected. Choose the move tool(shortcut V) and click elsewhere on the document. Your shape should now have a simple outline.
Grab the direct selection tool(shortcut A) and try clicking once on the shape's outline. You'll notice that four small square icons appear in the corner of the shape. If you click+drag you can reshape the square by moving where the line segments meet.
All vector shapes are created using these points called anchor points. Through either a curve or a line it's possible to create every vector object you can imagine. Please skim through this excellent post which delves further into vector shapes.
To add new points into the shape you'll need to familiarize yourself with the pen tool.
Pen Tool Fundamentals
The pen tool in Illustrator works similar to that in Photoshop. I recently covered tips for the PS pen tool and how beginners can get started. Illustrator works with similar tools but in a different context.
So in this case we want to add a new anchor point into our square. Select the pen tool(shortcut P) and click anywhere along the shape's border. You'll notice the pen tool icon gets a little plus sign next to the cursor. You can simply click to create a new straight point. This will appear as another little blue square around the shape's exterior.
But if you want to make it curved you'll need to use the anchor point tool(shortcut SHIFT+C). This turns your cursor into a thin arrow which is meant for anchor point manipulation. If you click+drag the anchor point you'll get two bezier handles which appear outside the shape.
By default these do not appear unless you specifically drag them out of the anchor point. Once they're out you can use the direct selection tool to move either one which adjusts that side of the curve. It's a very powerful tool which requires some practice to understand.
If you're brand new to the pen tool I suggest you follow this quick exercise created by Tuts+. You'll be guided through a series of steps for tracing letters to create your own custom vector shapes. The learning curve is steep, but once you understand path creation you'll be able to apply this knowledge onto every vector project in the future.
Customizing .AI Files
Designers frequently release their own freebies online to the community. Sometimes these are used in web projects while other times they're used as learning resources. Either way freebies are great to start playing around with vectors in Illustrator.
I'll be toying with this free iconset released on Dribbble by Pavel Kozlov. Once you download the .zip file you'll notice there are Illustrator files for the line icons & colored icons. These two styles are predominantly used in flat interfaces such as iOS.
Since we've already covered paths and basic selections it should be easier to mess around with these icons. Keep in mind I don't expect you to understand what you're doing at this point. You should only be familiarizing yourself with Illustrator and how the different tools work.
I've opened the .AI file of colored icons and and zoomed in closer to examine each shape. Grab the direct selection tool and start clicking on different elements. You should realize that vector icons are made up of many smaller shapes pieced together with fills and strokes.
When messing with these icons get as close as possible to really examine how the anchor points join together. Some designers prefer to create shapes with strokes while others use natural fill colors(and some use both!).
By clicking onto the bezier hands you can see exactly how the curves are formed.
If you haven't done so already try finding an anchor point and clicking with the direct selection tool. Then locate one of the bezier handles and ALT+CLICK to drag only one side. The direct selection cursor will have a plus sign located beside the icon.
This exercise is not meant to have you create brand new icons from scratch. In fact, icon design is one of the toughest skills to master and often requires some knowledge of traditional drawing/sketching. But if you can see how icons are created you may be able to duplicate these effects to style your own unique icons.
Illustrator is an incredibly complex program but it's undoubtedly a favorite among designers. Vector workflow is an acquired skill which always starts from learning the basics.
If you want to improve your skillset be sure to practice guides & tutorials online, along with finding extra time to play and build on your own. At first it all seems very complicated but once you understand the fundamentals you'll be able to comprehend more information quicker than you'd expect.