Processing: Creative Coding and Computational Art

Springy Dude is not an accurate physics simulation. Instead, I used some random values as
an approximation for the spring and deformation. When the mouse moves, the entire
polygon springs, based on the original springing code we looked at earlier in the chapter.
The block of code controlling this overall movement is the following:
// move center point
float deltaX = mouseX-centerX;
float deltaY = mouseY-centerY;
// create springing effect
deltaX *= springing;
deltaY *= springing;
accelX += deltaX;
accelY += deltaY;
// move polygon's center
centerX += accelX;
centerY += accelY;
// slow down springing
accelX *= damping;
accelY *= damping;
I utilized a parenting approach with regard to the relationship between the polygon’s five
perimeter points (which aren’t rendered) and the shape’s central point. If you haven’t
done much computer animation before, this may not initially mean much to you. The central
problem in a sketch like Hybrid Springy Dude is how to maintain the shape, while
allowing both the form to move as a whole and its individual parts to move independently.
In a program like Flash, there are MovieClip data structures that can explicitly have parent
and nested child clips. Most 3D animation applications employ similar constructs. In
Processing, we don’t have this built-in structure (though of course we could build one).
Instead, in the example I used the variables centerX and centerY to represent the overall
coordinating point of the entire shape, which in a sense becomes the parent (or control
node).
I used trig functions both to calculate the nodes’ starting positions (relative to the shape’s
center point) and to create the spring effect on the shape’s vertices. To enable the shape
to return to its original polygonal structure after the springing, I needed to capture the
original point locations of the shape (relative to the control node). Here’s the block of
code that does that:
// calculate node starting locations
for (int i=0; i