After clicking on the radio button in the Selection Panel to choose a transformation, you see within
this scrollable window the OpenGL function call for that transformation. You choose the parameters passed to the
function by placing the mouse over a value initially displayed in green and with the left button down,
drag the mouse up and down. The result of the change appears in the display window with the triangle
changing according to your choices.
Initially, as is always the case, the pivot point (fixed point) is at the origin. You can change
the location of the pivot point. After making that choice in the selection window, the parameter input
display provides for selecting the x and y coordinates of the pivot point. As you change these values,
the yellow dot in the display window will move accordingly.
As with other tutorials, you can also change a selected item (drawn in yellow) using the Up-Arrow and Down-Arrow keys. The amount added to or subtracted from the selected item is fixed within the program. However, a multiplier is also used in making the change. You may adjust the multiplier through the Page-Up and Page-Down keys. Making the mulitiplier larger accelerates the change that is made to the selected item.