Tuesday, October 8, 2013

Digitizing hand-drawn art - part 2 - Bézier curves, pathfinding

Here's a link to Part 1. In short it suggests using a real scanner and the LiveTrace tool in Illustrator.

So, again, scanner is essential. I use a $50 Canon and the results are always much better than taking a photo with my DSLR camera or especially phone camera - mostly because there will be no warping of the image.

For me, there are 2 types of sketches - perfectly drawn through, inked ones and messy scribbles. Like this:


The first sketch is clean, inked, and finished - the only thing left to do is to color it. In this case I should be fine using the LiveTrace tool. This is best for people preferring to do most of the work on paper and to deal with Illustrator as little as possible.

The second sketch on the other hand is a real mess - parts of it are drawn with a pencil and the rest with a pen. All lines are messy and not drawn out. Some details are just not there, and some need to be redone. LiveTrace is really not an option here because the sketch is loose and not finished. To deal with this kind of sketches I will need to do 95% of work in Illustrator. Here's what you need to do.

1. Draw your sketch - don't worry about it being messy or having some curves done wrong. You can make a clean sketch like the bear one and still use this method - it's up to you. The point is you don't have to.

2. Scan your sketch, place it in Illustrator on the bottom layer (and set the layer to template or make it semi-transparent).

3. The sketch will be your guide. The idea is to build that with Bézier curves, basic shapes like elipse, rectangle etc., and the use of pathfinder panel tools. So really it's a combination of different things and you yourself can decide which of the three to use and when. But you should be familiar and comfortable with Bézier curves and pathfinder tools. If you are not, I strongly recommend investing some time into it. In a long run it will save you a lot of headache and trouble.

If you choose this method, you will have 100% control of every tiny detail and curve and can readjust things quite easily. Also readjusting one thing won't "break" other parts.

Here's an example.



On the left is my initial pencil sketch scan. On the right is most of the artwork built with curves and shapes. Notice that everything in the right picture has no fill and precisely the same outline (0.5px plain solid #9E005D). I save that as a graphic style and always use it when I work with this method.

And here is the end result.



Everything is a separate path that I can easily control and modify at any time with no hassle or inconvenience.

When you have a sketch that you use like a template or a guide it is a lot easier to just build paths by points with the Bézier curves rather than using a stylus and the pencil or brush tool. That's also a way to do things but I personally like doing that when I don't have a sketch and am drawing something in the Illustrator from the start.

Bézier curves


(You should watch this in full screen mode)


Use the Pen tool (P) to build a path point by point.

You can add/remove points later with Add Anchor Point (+) and Delete Anchor Point (-) tools (they are in the Pen drop down menu but really you should use the + and - keys).

Each point will have 2 handles - they control curve segments directly to the right and to the left of the point. Use Direct Selection (A) for selecting a specific point (or multiple points). If there are no handles on a selected point it means it's a corner - you can convert it to a smooth point with the Convert Anchor Point Tool (Shift C) or if you have Direct Selection it will show up on the Control panel.

The way Convert tool works is you hold down on an anchor point and drag in any direction - it will convert the point to a smooth one and 2 handles will appear. At first the handles are connected and dragging one around affects the other. If you want to break that, use the Convert tool to drag one of the handles - after that they will move separately from each other. If it's a smooth point you can convert it to a corner one by just clicking with the Convert tool on the point directly.

Placement of points is crucial. There is no rule about it however I prefer to have as little anchor points as possible - it's easier to control the path that way. There is sort of an unwritten rule called "rule of clocks" or something like that. It says if you can fit an imaginary wall clock (elliptical, not necessarily round) into a piece of the curve, that curve needs to have anchor points on 12, 3, 6, 9 o'clock points. You sort of rotate the imaginary clock - so 12 doesn't necessarily appear on the top. It's hard to explain with words so here's a drawing :)



The red path is your curve. It has 6 anchor points - start point, 3, 9, 6, 3, and end point. I could have put another anchor point (or added an imaginary clock) into the curve right before the end point - but it was unnecessary since it's the last 'segment' and i could achieve the desired result by adjusting handles on the end point.

If you regard this path as a  function, you need to have an anchor point on every point of extreme - every maximum and minimum of the function, or every peak and valley.

Don't think too much about this - just get a feel, add points remove points, play with the handles.

Pathfinding


(You should watch this in full screen mode)


Open the Pathfinder panel. The first line on that panel says "shape modes" and has Unite, Minus Front, Intersect, and Exclude buttons. Sometimes it's easier to build a shape by breaking it down into simpler shapes and joining them - for instance, if you are drawing a heart, the easy way to make it perfect would be to draw a circle and a triangle, Unite those shapes, and then reflect the united shape. Then unite 2 pieces of hearts and voila - you have a perfectly symmetrical heart.

Minus Front is like a cookie cuter - the shape that's in front will be subtracted from the shape underneath.

Intersect works like an AND operator in programming and logic. If you have 2 overlapping circles and click Intersect you will have a new shape that's the overlapping area of the 2 circles.

Exclude will do the opposite - it will unite the 2 circles and subtract the overlapping area.

One thing to keep in mind - when you use the pathfinding method it's a good habit to copy and paste in front the 2 shapes you're working with. Because, for example, when you use the Minus Front button you will lose the shape in the front - and if you have other future uses for it it's best to have a copy. The copy or the "throw-out shape" has only one use - to modify some shape.

Know your tools and hot keys!


Most of the books on Adobe Illustrator explain every tool in depth but don't do a good job explaining when and why you should use them. That is what I'm targeting in this tutorial - I'm hoping it will give general guidelines and ideas on how to accomplish your goal and how to work with the tools. Once you understand when and why to use certain tools you should read up on those in your Illustrator book or online - there's plenty of material on that.

Hotkeys are important - it saves a lot of time to push a button on the keyboard rather than selecting a tool on a panel with the mouse cursor every time. However, I strongly discourage getting a list of shortcuts and trying to memorize them. You should learn the hotkeys naturally - by use. You will notice that there are a lot of tools that are used very frequently - like Direct Selection, Selection, Pen, Ellipse, etc. just pay attention to the tooltips when you go and click on a tool. You will learn the important hotkeys overtime and with no effort.

Practice makes perfect - do a couple examples from here and there. Start with a simple sketch, then move on to more complex artwork. Explore the tools and options, try different techniques, see what you like and what you don't like. There is no right or wrong way of doing things - you can accomplish the same result through different methods - just some may take a lot more time than others.

Ah yeah, and here's the final graphic for the squirrel sketch. I was lazy I didn't do highlights and shadows on the squirrel. :)





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EDIT

In the Bezier curves part of this tutorial I was writing about the clock method and described it as an unwritten rule. That was my bad - it's Von Glitchka's Clockwork Method (TCM). I accidentally stumbled upon his video lecture on Lynda.com once and later I bought one of his books (Vector basic training). I'd recommend that book to anybody who hasn't read it. It focuses more on the whole creative process rather than explaining what each tool does. And gives perspective in general on some techniques. Anyway. I just didn't realize TCM was Von Glitchka's method and assumed it's just a rule of thumb.

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