We set here the boundaries and dimensions of the viewport that covers the left half of the device window. After which, we call the function that creates (defines) the geometry.

The left and bottom boundaries of the viewport are 0's. But for consistency in using percentages for the values, we give the values as 0.0 times the corresponding device window dimensions. Further, the type cast to int is used so as to avoid a possible compiler type conversion warning. Last, since we want the viewport to cover the LEFT half of the window, keeping the same height, we use 0.5*deviceWindowWidth as the width of our viewport.