\chapter{Streamtubes}

The last of the non-optional assignments. This is, just as the height plots, a 3-dimensional assignment although streamlines and streamtubes can be used in 2D
grids. \\

\section{Description}

Imagine you drop of bit of ink into the fluid and let it flow for a while. What you will get is a line that shows the path a ink particle has taken. Such a path is
called a streamline. A streamtube is a 3D variant of a streamline. A streamtube consists of a number of consecutive tubes that together form a thick 3-dimensional
flexible tube. \\

Each streamtube has a begin and end. The begin point of a streamtube is called a seedpoint. From a seed point the tube will begin flowing with the fluid. It ends
after a number of frames, seconds or parts. This can be variable. \\

The streamtubes we had to implement were'nt actually flowing trough the fluid but through a frame history. Each frame is stored in a history array and the
streamtubes take a path trough history. The 2D grid became a 3D grid with this new feature. \\

\section{Implementation}

First we implemented the placement of the streamtubes. We chose to let the user be able to point the exact position of each seedpoint by mouse. A seedpoint is
rendered as a small sphere. \\

We also created a history array that stores up to 50 frames. \\

\section{Difficulties}

We did'nt have enough time to actually trace a streamtube. \\