title: Making a histogram of how many particles (x,y,z, and time) pass through different defined 3D regions
body: <p>How would you go about creating an algorithm that does the following; makes a histogram of how many particles (x,y,z, and time) pass through different defined 3D regions. Are there any analogous problems I might look at?</p>
  <p>To put in other terms, if baseballs were thrown all over the house, knowing the baseball's positions and the dimensions of the rooms in the same coordinate system, how many baseballs passed through the living room, the dining room or the kitchen?</p>