Unity Game Optimization - Third Edition

Using distance-squared over distance

It is safe to say that CPUs are relatively good at multiplying floating-point numbers together, but relatively dreadful at calculating square roots from them. Every time we ask Vector3 to calculate a distance with the magnitude property or with the Distance() method, we're asking it to perform a square root calculation (as per Pythagorean theorem), which can cost a lot of CPU overhead compared to many other types of vector math calculations.

However, the Vector3 class also offers a sqrMagnitude property, which provides the same result as distance, only the value is squared. This means that if we also square the value we wish to compare distance against, then we can perform essentially the same comparison ...