Sky-paper is 3DTop's equivalent to Wall-paper.
3DTop wil draw a gigantic sphere around your 3DTop-scene with a texture. You might already have noticed that right-clicking on 3DTop while no object is selected will pop-up a menu with some general items. you can define the texture by choosing "Load sky-paper..." .
When you choose this item you can select a Windows bitmap as a texture. No constraints are put on the size or number of colors by 3DTop, but be careful that some drivers (TNT) can not handle textures bigger than 512 x 512 pixels.
After you've chosen a texture the following sub-menu's will appear:

- Off
When you've chosen a Sky Paper you can switch it off with this item.

- Edit Tiling and height...
This will enable you to choose the tiling and height of the sphere. You'll notice that the mouse-pointer changes its shape into a left/right/up/down arrow, this means that by moving the mouse left or right you change the tiling and by moving the mouse towards you or away from you, the height of the sphere can be changed.
When you are content with the tiling and height you've chosen, press the left-mouse-button once. If you would like to cancel the whole operation press the right mouse-button once.

- Load other...
When you choose this item you can select another Windows bitmap as a texture. No constraints are put on the size or number of colors by 3DTop, but be careful that some drivers (TNT) can not handle textures bigger than 512 x 512 pixels.

A tip: Bitmaps are internally stored in OpenGL with a width or height that is a power of 2. So if you have a bitmap with the size of for example 312 x 260 it is stored with a size of 512 x 512. This is not very effective in terms of memory-usage. It is best to resize the bitmap to say 256 x 213 and create the sky-paper with this resized bitmap, this causes the bitmap to be stored as a 256 x 256 bitmap.
Power of two is: 2 , 4 , 8 , 16 , 32 , 64 , 128 , 256 , 512 , 1024 , 2048 etc.