Efficient way of finding distance between two 3D points

Question

I am writing a code in C++ and want to compute distance between two points. Question 1:

I have two points P(x1, y1, z1) and Q(x2, y2, z2) , where x,

Answer 1

There are faster ways to get an approximate distance but nothing built into the standard libraries. Take a look at this article on FlipCode that covers the method for fast 2D distances. It essentially collapsed the sqrt function into a compound linear function that can be quickly calculated but isn't 100% accurate. However, on modern machines these days fpmath is fairly fast so don't optimize too early, you might find that you're fine taking your simple approach.