This effect causes the output window to be divided equally into four rectangles or quadrants. Only the upper-left quadrant is drawn to in this mode; the other three quadrants are mirror images of the upper-left, as shown below:
|upper right||upper left, flipped horizontally|
|lower left||upper left, flipped vertically|
|lower right||upper left, flipped horizontally and vertically|
The result is similar to a kaleidoscope. Note that since origin motion still ranges over the entire canvas, it's possible to hide some or all of the Whorld image, by placing the origin in any quadrant other than the upper-left. Pleasing results can often be obtained by moving the origin along the edges of the upper-left quadrant, especially when damping is used.
To enable/disable mirroring, use Image/Mirror or F5.
Mirroring performance depends almost entirely on the capabilities of your graphics card. Most 2000/XP-era PCs should be able to handle it acceptably, but if not, try upgrading your graphics card first before upgrading anything else. Mirroring may also be affected by the DirectDraw options.