Interactive Viewport - When active, the Terra object in the viewport will be updated immediately as you paint the terrain. Also, a small cross will be displayed over the terrain, with its size proportional to the brush radius. This option can slow down painting, so use it with caution.
Show Navigator - The Navigator is a tool that helps you to move across the terrain even when you're using very high zoom values. By moving the rectangle inside the Navigator window, you will pan the terrain inside the Terrain Editor interactively. You may also alter the Terrain Editor's magnification factor by using the Navigator's Zoom slider or by entering an integer value in the Zoom Edit box. In addition, you can resize the Navigator dialog box by dragging any of its corners.
Monochrome - This option will use a monochrome scheme instead of the Gradient for the Terra Editor. A black color represents a minimum height value, while a white color represents a maximum height value. Checking this option Off puts your Color Gradient back in effect.
Grid - Opens the Grid dialog box where you can alter spacing and color of the Preview window grid. To enable or disable the grid, use the Display checkbox.
Zoom In - Multiplies the magnification factor by two. The point of magnification is the central pixel of the Terrain Preview window.
Zoom Out - Divides the magnification factor by two.
Refresh - Updates the Terrain Preview window.