Processing: Creative Coding and Computational Art

PROCESSING: CREATIVE CODING AND COMPUTATIONAL ART
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I used p4 to its left, I chose to go back to the beginning of my curve, ensuring that p4 had
a control point to its right. (I know this is confusing and not intuitive at all.) One other little
trick that may make this more comprehensible is that if you copy the third through the
eighth parameters of a curve() function call and paste them in another curve() call, then
the curves will connect. You’ll still need to add a seventh and eighth parameter to this new
curve. Look at these two lines:
curve(p0.x, p0.y, p1.x, p1.y, p2.x, p2.y, p3.x, p3.y);
curve(p1.x, p1.y, p2.x, p2.y, p3.x, p3.y);
Notice how the third through eighth parameters in the first curve() call repeat as the first
through the sixth parameters in the next curve() call. I still need to add the last two
parameters to the second curve, which I do by continuing the cycle from p3 to p4 for the
seventh and eighth parameters:
curve(p0.x, p0.y, p1.x, p1.y, p2.x, p2.y, p3.x, p3.y);
curve(p1.x, p1.y, p2.x, p2.y, p3.x, p3.y, p4.x, p4.y);
Finally, there is one other cool function available to control the tension of the spline curve;
it works similarly to how control points on a Bézier curve exaggerate or flatten a curve,
depending upon where the handles are located. Using curve(), you don’t literally drag any
handles or set extra control points off the curve. Instead, you simply pass a value to the
curveTightness(value) function. The value can be negative or positive. In this next example
(shown in Figure 7-31), I create a series of identical spline curves, with varying degrees
of curve tightness, using the values -2, -1, 0, 1, and 2 as arguments in the
curveTightness(value) function (please note that you need to use Processing’s noFill()
function if you don’t want your curves filling in):
// Catmull-Rom spline curve
// Curve Tightness
size(600, 400);
background(0);
stroke(255);
strokeWeight(2);
smooth();
int curveWdth = 50;
int cols = 5;
int xPadding = (width-curveWdth*cols)/(cols+1);
int x = xPadding;
for (int i=-2; i