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What is the logic of bezier curves? (for Illustrator pen tool)

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superboyac:
I've never quite gotten the hand of bezier curves, and it's a mental block.  I keep trying the tutorials, but I don't have the time to really do enough practice for me to get it naturally.  But, I know how I think...I need a logical explanation of how bezier curves work.  I don't want just practice, I want an explanation of the idea.

Like, "When a handle is like this, it is doing this and this, so it makes this sort of shape."

Anyway, I'm looking for good explanations.  There are tons of tutorials and explanations of how to get a shape, but hardly anything that just explains what it is and how all the parts work.

Wikipedia has some good, helpful animations.

superboyac:
I find this image useful:


So from what I gather, it seems for each segment you dray, there's only a certain number of shapes that can be accomplished.  I need to understand these individual shapes.  I think what's confusing me are all these tutorials where they show you how to draw a whole thing, but I just need to understand what each segment can do, and I'll be able to go from there.

tomos:
My approach is always dive in at the deep end and see how it goes.
Occasionally though, I do miss something fundamental or very helpful with that approach...

Have you tried doing that - just going in the deep end and using the pen tool?
AFAIK up to CS4 the only qualifier key is the Alt key (I havent used more recent versions, and tbh, I still use FreeHand when drawing).

1) Click to make the first point in the line.
2) Click to make a second point, *but* hold the mouse button down. Now try dragging: the point you made stays where it is, but the drag extends the 'handle' (called 'direction line' in your image above) and the curve changes. Let go at some stage :-) and the curve is decided (can be changed later though).
3) Now create the next point - this time try pressing the Alt key when dragging the 'handle' - the handle changes from a straight line to an angled line. Try letting go of the Alt key (keeping the mouse button pressed the whole time) and then pressing the Altkey again. The new angled handle will change the next part of the curve when the next point is created - sort of like creating an 'm' curve.

Note: if you dont do the drag thing you will have straight lines between points.

Okay: you've posted again - basically you can create any curve: some curves will need more points which can only be figured out by trying it. A good way of seeing what can be done (and figuring out how to do it) is to trace something e.g. import a bitmap image and trace.

ewemoa:
Does this help at all?

Bezier Curves and Surfaces: An Intuitive Approach

mouser:
This would be a nice time for our beloved favorite digital artist Nudone to drop by and share some thoughts.. He sure knew how to make curves "sing".

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