Latex flowchart figure

Many times a figure is too long for a paper, such as a flowchart. In this case, we have to put the figure horizontally to save space, like the overview in the HOG paper. To do this, we need to use \begin{figure*} instead of \begin{figure}, to ensure that the figure spans two columns. Moreover, we use [t!] to put the figure at the top of the page. Sometimes the figure appears at the next page of where it is referenced. To solve this, place the figure \begin{figure*}[t!] somewhere before it is referenced, eg in the previous page. It turns out that the figure position has nothing to do with where it is referenced, but depends on where it is included.