1.9 Static vs. Non-Static Functions

[vihren-milev]

Hi Daniel,

This is a great book. Thanks for publishing it.

I was going through the first chapter while writing my own code in Java and noticed something rather inefficient in "1.9 Static vs. Non-Static Functions".

The problem is that these static methods create new instances of PVector every time you call them, which could happen 60 time per second when you animate a moving object and a lot more frequently if you have a complex scene. These temporary objects would soon have to be discarded and there would be a lot of work for the Garbage collector.

As an alternative I would recommend using a copyFrom method similar to this:
PVector copyFrom(PVector v) {
x = v.x;
y = v.y;
return this;
}

That method can be combined with using a temporary vector that is reused over and over without having to instantiate new objects. For example:
class MyAnimation
{
PVector v;
PVector u;
PVector tmp;

public MyAnimation()
{
    v = new PVector(0,0);
    u = new PVector(4,5);
    tmp = new PVector(0,0);
}

void update()
{
    tmp.copyFrom(u);
    tmp.add(v);
    // At this point you have the sum of u and v in tmp
    // while the original two vectors remain unchanged
}

}

Hope this helps,
Vihren

[Daniel Shiffman]

Thanks for this suggestion. I've addressed this a bit in 6.4. You can also use set() instead of your own copyFrom() function.