Is mouse over sphere in 3D?

I have a sphere somewhere, and its location is known. However, I'm also using PeasyCam, so a problem remains - I don't know the camera vectors. So, how to check if the mouse (or any other vector for that) is over the sphere?

My code so far-

import peasy.*;

PeasyCam cam;

float x = 0, y = 0,z = 0;

void setup(){
  size(720, 720, P3D);
  cam = new PeasyCam(this, 200);
}

void draw(){
  translate(x, y, z);
  sphere(100);//being minimalistic

  x += sin(y);//random methods, real code is different
  y += cos(z);
  z += random(1);

  println(mouseOverSphere(x, y, z, 100);
}

boolean mouseOverSphere(float posX, float posY, float posZ, float size){
  //What to do here??
}