When to use the epsilon machine and when not to use it?

Question

I am reading a book on 3D rendering, and the author sometimes uses epsilon, and sometimes not.

Pay attention to ifthe beginning using epsilon, and the other ifthat does not.

What is the logic behind this? I see that it avoids any possibility of dividing by zero, but if epsilon is not used in the function, there is a chance that it will return a value that causes the external code to divide by zero.

The book is a real-time rendering of the third edition, by the way.

Answer 1

if(|f| > ϵ) , f 0. , f.

, ϵ.

,

if(t1 > t2) swap(t1, t2); 

- , , . , 0, ϵ.

, , , .