+In addition there is a \textit{Markers} and a \textit{Boundary} checkbox which come in handy to turn off the display of the points and the outline of the mask. Turning off \textit{Markers} is very useful when you have a lot of control points that clutter the display and make it more difficult to see the actual mask. A helpful feature is available by disabling \textit{Markers} and enabling \textit{Boundary} which results in all masks being displayed in the viewer; for example you can then see mask 0, mask 1 \dots at the same time.
+
+A \textit{gang} symbol on the right hand side of this section, tooltip of \textit{Gang points}, is another useful feature that makes it easy to drag a mask to an exact coordinate using the \textit{X} or \textit{Y} textbox for numerical input or the associated tumblers. This works like the \texttt{Alt+LMB drag} translate but provides the ability to be precise.
+
+\subsubsection*{Pivot Point section}%
+\label{ssub:pivot_point_section}
+
+The \textit{X:} and \textit{Y:} coordinates mark the value of the current \textit{Pivot Point} used for rotation, scaling, and translation. You can either directly key in numerical values or use the tumblers to change the values as long as the \textit{Focus} checkbox is checked.
+
+The \textit{Focus} checkbox is used in case you want to set a different point in the Compositor for pivoting instead. And the \textit{Gang} symbol for rotate/scale/translate means that these operations will be performed on all points of the enabled masks. The gang symbol is surrounded by a gold colored background when it is in effect. When performing a rotate operation on a mask with the mouse wheel, \textit{acceleration} is in effect -- this means the faster you wheel, the more space is covered so that you do not have to wheel dozens of time to make a full rotation. Then when you wheel around slower, you can fine tune the result.
+Note that in order to be able to rotate/scale around pointer, the Focus checkbox must be unchecked.
+
+\subsubsection*{Other sections}%
+\label{ssub:other_sections}
+
+Finally there are the \textit{Apply masks before plugins} and \textit{Disable OpenGL masking} self-explanatory checkboxes.
+
+Note: Not all OpenGL software can support the current masking methods. If your opengl implementation does not support Shader Version 4.3 or has trouble with this (it is relatively new to opengl at the time this was implemented), then this checkbox will allow you to use the software masking to avoid any potential issues. Normally, OpenGL is probed for the shader version and will automatically use the software implementation if required.
+
+The \textit{Help} checkbox can be enabled in order to see a list of the keys used to perform various operations. If you use Masking infrequently, these are a valuable reminder to which key combinations to use. Currently they are as follows:
+
+\vspace{2ex}
+\begin{tabular}{ll}
+ \hline
+ Shift+LMB & move an end point \\
+ Ctrl+LMB & move a control point \\
+ Alt+LMB & to drag translate the mask \\
+ Shift+MMB & set Pivot Point at pointer \\
+ Wheel & rotate around Pivot Point \\
+ Shift+Wheel & scale around Pivot Point \\
+ Ctrl+Wheel & rotate/scale around pointer \\
+ \hline
+\end{tabular}
+
+\subsubsection*{Key Alternatives}%
+\label{ssub:key_alternatives}
+
+\vspace{2ex} Note: For some desktop window managers, certain keys may already be in use by the operating system, so you will either have to redefine them in your desktop or use different key combinations. For example, at least some desktops used with \textit{UbuntuStudio 16.04} and \textit{Arch} field the \texttt{Alt} key, thus requiring alternative key combinations to be needed. Below are some of these alternatives.
+
+\vspace{2ex}
+\begin{tabular}{lp{11cm}}
+ \hline
+ LMB & move/create an end point (to move the end point the pointer must be above the point) \\
+ Shift+LMB & move an end point (the pointer may be near the point, not above it) \\
+ Ctrl+LMB & move/create a control point \\
+ Alt+Ctrl+LMB & to drag translate the mask \\
+ Shift+Key Delete & to delete the mask \\
+ Shift+MMB & Set Pivot Point at pointer \\
+ Alt+Wheel & zoom in/out the screen (also available in Ubuntu16 but does not exist in all distros) \\
+ \hline
+\end{tabular}
+
+\vspace{2ex}
+Focus checkbox = unchecked:
+
+\vspace{2ex}
+\begin{tabular}{ll}
+ \hline
+ Wheel & rotate around Pivot Point \\
+ Shift+Wheel & scale around Pivot Point \\
+ Ctrl+Wheel & rotate around pointer \\
+ Ctrl+Shift+Wheel & scale around pointer \\
+
+ \hline
+\end{tabular}
+
+\vspace{2ex}
+Focus checkbox = checked:
+
+\vspace{2ex}
+\begin{tabular}{ll}
+ \hline
+ Wheel & rotate around Pivot Point (“Custom focus point”) \\
+ Shift+Wheel & scale around Pivot Point (“Custom focus point”) \\
+ \hline
+\end{tabular}
+
+\vspace{2ex}
+
+\subsection{Cropping}%
+\label{sub:cropping}
+
+Cropping is used to reduce the visible picture area by changing the output dimensions, width and
+height in pixels, and the $X, Y$ values. An example of cropping and the crop menu is seen in
+figure~\ref{fig:cropped_area}.
+The easiest way to use cropping is to click with the LMB
+at the spot to begin cropping and while holding down the LMB, drag the mouse. This creates a rectangular
+cropping area. To change the size/location of that area, click on any of the 4 corner points
+with the LMB and drag. While dragging, you will see
+the X1, Y1 coordinates and W for width, H for height, in the Crop tool popup menu
+automatically change numerical value to reflect the current position. For precise locations, you
+can keyin exact values into those textboxes instead of using the mouse.
+Once you have the crop area defined as you want it, then click on the \textit{Apply} button to have
+the actual cropping take affect.
+
+There are 3 choices of crop methods to choose in the menu pulldown on the bottom right side.
+\begin{enumerate}
+ \item Reformat - Reformat Session crops and changes the Format for the entire session.
+Because the Format is changed, this is applied to all tracks in the project.
+The part of the image outside the rectangle will be cut off and the projector will make the video fit.
+The \texttt{Settings $\rightarrow$ Format} window will show the new project Width and Height values and
+the projector tool window will show the new $X, Y$ values. Track size remains unchanged.
+You can undo the cropping by entering the original project dimensions in the
+\texttt{Settings $\rightarrow$ Format} window for the Width and Height. You will also have to use the Projector
+tool in the Compositor toolbar to \textit{Ajdust projector automation} by clicking on the Reset icon.
+ \item Resize - Resize Projector; to undo this, enable \textit{Adjust projector automation}
+and do a Reset.
+ \item Shrink - Resize Projector and Camera; to undo this, enable each of the \textit{Adjust
+projector and camera automation} tools, one at a time, and do a Reset in the menus.
+\end{enumerate}
+An important note here is that the original aspect ratio will be maintained so if your frame is
+rectangular (as many are) and you "crop" by surrounding the region of interest with a square,
+the cropped area will be more than you marked in order to keep the aspect rectangular shape.
+The Resize and Shrink options are applicable to all video tracks except the disarmed ones.
+This is in contrast to the Reformat option, as mentioned previously, which applies to all tracks even if disarmed because it changes the Format for the session.
+One last note of interest, this cropping is keyframable.
+
+\begin{figure}[htpb]
+ \centering
+ \includegraphics[width=0.9\linewidth]{cropped_area.png}
+ \caption{Crop menu and outlined crop rectangle on the right side}
+ \label{fig:cropped_area}
+\end{figure}
+
+An easy to follow step by step usage of the cropping tool is outlined next.
+\begin{itemize}
+ \item Enable the crop tool in the compositor window to display the Crop popup menu.
+ \item Click-drag in the video to define the crop area which draws a rectangle on the video.
+ \item Click-drag in the video to start a different rectangle instead.
+ \item Click-drag on a corner of the rectangle to reposition that corner.
+ \item Alt-click in crop rectangle to translate the rectangle to a different position without resizing.
+ \item The crop popup menu allows text entry of the top left coordinates ($X1,Y1$) and width and
+height ($W, H$) that define the crop rectangle.
+ \item Choose one of the 3 options of Reformat, Resize, or Shrink.
+ \item When you have the rectangle where you want it,
+click on the \emph{Apply} button in the menu to actually perform the crop operation.
+\end{itemize}
+