i believe its done by adding more and more segments to beziervertext
http://processing.org/reference/bezierVertex_.html

ok, thank you! ..i thought it might be possible, as in most standard vector software, to draw a single line just with several points...

holger wrote on Sep 1^st, 2009, 3:21am:
I can only guess, but I strongly suspect they just hide the fact there are several Bézier lines by treating them as a whole. But in general, you can click in the middle of a complex curve, on a node, and decide there will be a sharp angle there (tangents are no longer aligned) or even separate them.

Quote:
It doesn't do magic. If you look at the code, you will see I used my helper functions (of same names, but with an initial capital, per my old habit) instead of Processing's ones (which are used internally, of course). Beside, as I said above (in a clumsy way), I use bezierVertex() instead of bezier(), as it is easier to chain them.

I drew a heart (which I animated) as one of my first Processing sketches, not sure if I ever shown it in this forum.
The heart (sic...) of the sketch is:
Code:

    beginShape();
    // The heart, symmetrical around vertical axis
    // Anchor point (highest sharp point)
    vertex(m_x, m_y);
    // Top left part
    bezierVertex(
	  m_x, m_y - m_topVectorLen,  // Upward control vector
	  m_x - m_size, m_y - m_topVectorLen,  // Idem
	  m_x - m_size, m_y);
    // Bottom left part
    bezierVertex(
	  m_x - m_size, m_y + m_topVectorLen,  // Downward control vector
	  m_x - m_bottomVector_dx, m_y + m_bottomLen - m_bottomVector_dy,
	  m_x, m_y + m_bottomLen);
    // Bottom right part
    bezierVertex(
	  m_x + m_bottomVector_dx, m_y + m_bottomLen - m_bottomVector_dy,
	  m_x + m_size, m_y + m_topVectorLen,  // Downward control vector
	  m_x + m_size, m_y);
    // Top right part
    bezierVertex(
	  m_x + m_size, m_y - m_topVectorLen,  // Upward control vector
	  m_x, m_y - m_topVectorLen,  // Idem
	  m_x, m_y);

    endShape();
 

As you can see, I heavily parametrized it to allow easy customizations. The tangents here are either horizontal or vertical, so aligning them was quite easy.

You can export your drawing (in Illustrator, in Inkscape...) in SVG, Processing should be able to load and display it.

You might be interested by the Bézier Editor tool recently released.