Processing: Creative Coding and Computational Art

PROCESSING: CREATIVE CODING AND COMPUTATIONAL ART
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Figure 9-4. Ellipses with Bounding Boxes sketch
A bounding box is the smallest rectangular region that encloses a shape. Bounding boxes
are important in computer graphics, as it’s simpler and less computationally demanding
for the computer to calculate the area of a rectangle than an ellipse or some other irregular
shape. Thus, in a game, for example, collision detection can be calculated with regard
to the bounding box of a shape, instead of the shape’s actual perimeter. This will allow the
game to perform better (but there may be some loss of accuracy with regard to how the
actual detection looks on the screen).
In addition to the rect() and ellipse() shape functions, Processing includes point(),
arc(), triangle(), and quad() functions. I discussed point() exhaustively in Chapters 6
and 7, and technically a point is not a shape (mathematically speaking), so I’ll skip it. I also
covered arc() in the context of curves—but here’s one more example, illustrating the
arc() function’s pie shape feature (see Figure 9-5):
//Arcs with Bounding Boxes
void setup(){
size(400, 400);
background(255);
strokeWeight(10);
fill(127);
arc(103, 120, 130, 100, 0, PI);
ellipseMode(CORNER);
arc(103, 120, 130, 100, 0, HALF_PI);
ellipseMode(CORNERS);
arc(233, 220, 363, 320, 0, TWO_PI-HALF_PI);
// bounding boxes
strokeWeight(1);
noFill();