Vector Graphics Tutorial

(14/10/2005) Ok, this tutorial is back up again but still needs reformatting and tidying up. Apologies for any borked links.

Hi, due to popular request I have written a tutorial on vector graphics tool and how I use them to make piccys. It's ended up longer than I had intended, but I hope it is clear and proves useful to someone.

By vector graphics I’m talking about using mathematical curves to draw lines and area fills. When you draw using vectors, you create a series of points and curves around the edge of the object you’re creating, which describe its shape very precisely. If you are not familiar with this drawing technique, it may sound complicated, but it is actually a very intuitive and simple system, which is simple to pick up through practice.

The main reason I use vector tools is because above all else they allow me to create a very smooth line or fill quickly and simply. I usually don't make true, vector only, drawings, (the kind illustrators make for print quality graphics) as I am publishing most of my work on the web, and instead use a combination of both vector graphics and bitmap methods in Adobe Photoshop. The vectors provide the smooth lines and fills that are hard to create with a brush tool, and the airbrush creates the detail that would be time consuming to create with vectors.

Now in this tutorial I will assume that you know how to do basic things with a paintbrush and eraser (even if it’s just in MS paint), but that, like most people, you are unfamiliar with using vector graphics.

Personally, I use Adobe Illustrator, and Adobe Photoshop. I will talk with reference to these programmes, simply because I haven’t used anything else (other than flash, but I have always found the vector tools in flash to be pap), and assume some basic knowledge of how they work. I will also assume that other graphics software uses similar principles, should you wish to use them. Illustrator is designed solely for vector drawing, and is therefore a very powerful tool for this. Photoshop is designed mainly from the perspective of photo editing, but does have a variety of tools that make it very versatile, and amongst these are basic vector tools. Other software that uses vectors includes Freehand, CorelDraw, and Flash, and probably many more besides.

The basic tool you will be using is the pen tool. This is a rather stupid name for it, as it works nothing like any pen I’ve ever used. The only similarity it has to a pen is that the icon looks like a fountain pen. The mind boggles. You can use this tool to create shapes, and then control their form very precisely.

The pen tool works by allowing you to place things known as “anchor points”. In the most basic sense they are corners, but in smooth curves they also form the function of static points that allow you to control the curves shape.

To use the pen tool, move it around the edge of the shape you want to drawing, clicking it at corners or at changes in the direction of the curve. It will leave a series of anchor points, a bit like joining up the dots. Once you have completed a circuit of the object, either click on the start point to close the shape, or change tools to leave it open. You should have something that looks a bit like what you were drawing, but with straight edges and pointy corners. From now on I’ll refer to this as a “path” (as that’s what Photoshop calls them). A good way to practice this is by importing an image such as a photograph, and tracing round an object in it.

In Illustrator and Photoshop there are two basic tools for selecting your path, the black cursor (for selecting a whole path), and the white cursor (for selecting different components of the path). To select an entire path, for transforming, rotating, scaling, or colouring, simply click it with the black cursor. To select multiple paths drag over them, or shift click, via the standard computer selection rules. To select an individual anchor point or curve, for moving or reshaping, click it with the white cursor. In Illustrator you have to be very precise with this, or you can end up selecting the whole path (which is a bit fiddly and annoying). Again, to select multiple anchor points, drag over or shift click.

The next step is to turn your polygonal shape into a nice curvy one. To do this you need the convert anchor point tool; a thing that looks a bit like a chevron, or a normal cursor with the back missing. Click on an anchor point with this (again, you need to be very precise in Illustrator), and hold and drag. A little line will appear, from the anchor point, with two spots at either end. As you pull it, the straight lines will turn to curves. This is the basically a handle for altering the curve. Get the white selection cursor, and select the anchor point again. Then click and hold on one of the spots at the end of the handle. You will be able to adjust the curves sweep.
	At the moment both ends of the handle are linked. If you pull on one side, the other side will move in a seesaw motion with it. This is great for creating a smooth curve, but it won’t fit all curves you will come across. Get the convert anchor point tool again, and click and hold on one of the spots at the ends of the handle. Now move it, and notice that one side moves independently from the other. This gives a finer control over the curve, but may make it look less smooth.
Finally, to turn the anchor point back into a simple corner without handles, click on it once with the convert anchor point tool. Simple corners like this are need if you want to create a shape with straight lines.

There are two tools for doing this, both look like a pen, one has a plus sign on it, the other a minus. Guess which is which. To add an anchor point, click on the curve where you want it with the add point tool. A new point will be created, aligned to any previous shape the curve had. To remove an anchor point, click on it with the remove point tool.

You can also remove a point by selecting it and hitting delete, although note that this also deletes the curve connected to it as well.

As well as placing the anchor points one by one, you can take a short cut by using freeform pen tool. This allows you to draw the shape you want, and the software will place the anchor points in the curve for you. A little readjustment is all you need to get the curve you need. In Photoshop, this tool is called the freeform pen tool, and looks like a pen with a wiggly line on it. In Illustrator, it is called the pencil tool, and looks, strangely enough, like a pencil (although it is completely different to the pencil tool in Photoshop *boggle*). Using the freeform tool can speed things up greatly.

The pen tool can seem a little weird at first, if you’ve only used painting or airbrushing tools before, but it is remarkably simple to use when you get the hang of it. Like all things, the only real way to learn it is trough practice.

The trick with using paths is to try and use as few anchor points as possible. This allows you to quickly and easily reshape a curve, and keeps it looking smooth. After time you will learn where to put them to get the most control of the curve, and it is always recommended to keep them to a minimum.

Note that in both Photoshop and Illustrator you can transform, rotate, scale and distort and copy and paste paths in the same way as any other shape. Illustrator also includes a wide range of other tools for altering your curve.

In Photoshop, as it is not a true vector drawing programme, the paths are kept separate from the bitmap image. They have their own set of “layers” in the paths panel. Make sure you save and rename paths or groups of paths in this panel to keep track of them. Sometimes if you don’t save them (if the path name is "work path" ), creating a new layer or selection will erase them.

So what is the point of these curves that you’ve just created? Well, if your working in illustrator, this should be clear already. The curve you’ve created will be outlined or filled with different colours, depending on what is selected in the colour picker. The outline is called the stroke, and its width, or weight can be controlled on the stroke panel. The colours of both the fill and stroke can be altered using the colour panel. You can also copy the colour of another shape using the eyedropper. In Illustrator, there are whole panels with different styles and brush strokes you can apply to the path, for some quite impressive effects, although I am still getting to grips with these myself. For now I will just refer to them most basic fills and strokes.
	Of course if you are using Photoshop, the purpose of you path may be a little less obvious. It will look just like a fine, empty line, that won’t appear in your actual image if you were to save it as a .gif, for example. In order to create an actual stroke or fill from the path, you will need to manually create it.
Select your path, and go to the paths panel. There are four icons at the bottom. The black circle will fill the path with the foreground colour. The hollow circle will use the current brush to perform a stroke around the path. The dotted circle will turn the path into a selection. The circle with handles will turn a selection into a path.
	If you right click on a path layer in the path panel, and select “fill path…” or “stroke path…” you can set the default stroke or fill. Note there are quite a number of options for the stroke, allowing you to use paths to perform many fine adjustments to an image. The “convert to selection” option is also very useful for making precise selections for cropping images.

Once you have mastered the creation and use of individual paths, the next step is to get to grips with working with multiple paths. In order to get the image you desire, you have to take into account that objects at the front will block out those behind. Arranging multiple objects together is a skill in itself, but I will assume that readers of this either have basic experience of layers in graphics software like Photoshop, or in arranging objects in desktop publishers. These principles are basically the same.

In Photoshop, this is surprisingly easy. Paths are kept separate from the image itself, and only create an actual picture if you perform a fill or stroke. The trick is to make every individual stroke or fill into a separate layer. You can then change the layer orders to send them to the front or back of the image.

In Illustrator, it’s more complex. You have layers, but these can contain multiple objects, be they paths, imported images, or text objects. New objects always go to the front of the layer, so you will have to use the commands “bring forward” or “send backwards” in the object menu to make sure all items are arranged correctly. Layers themselves are more like large groups of objects, and an object in a layer above another object, will always be above that object, no matter how either is arranged in their own layer.

Also, because all your objects exist in the same working space, it can often be tricky to select the specific one you want. Illustrator has tools to deal with this, however. You can hide individual objects if they are in your way, by using the objects menu, or by clicking the eye next to them in the layers panel. You can also lock objects that you are satisfied with and don’t want to accidentally move. And you can group objects together for perform actions to all at the same time.