Wrapping (graphics)

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This article is about the technique used in 3D graphics. For wrapping in word processing, see Word wrap.

In computer graphics, wrapping is the process of limiting a position to an area. A good example of wrapping is wallpaper, a single pattern repeated indefinitely over a wall. Wrapping is used in 3D computer graphics to repeat a texture over a polygon, eliminating the need for large textures or multiple polygons.

To wrap a position x to an area of width w, calculate the value x' \equiv x \pmod{w}.

[edit] Implementation

For computational purposes the wrapped value x' of x can be expressed as

x' = x - \lfloor (x - x_{min}) / (x_{max} - x_{min}) \rfloor * (x_{max} - x_{min})

where xmax is the highest value in the range, and xmin is the lowest value in the range.

Pseudocode for wrapping of a value to a range other than 0-1 is

 function wrap(X, Min, Max: Real): Real;
   X := X - Int((X - Min) / (Max - Min)) * (Max - Min);
   if X < 0 then //This corrects the problem caused by using Int instead of Floor
     X := X + Max - Min;
   return X;

Pseudocode for wrapping of a value to a range of 0-1 is

 function wrap(X: Real): Real;
   X := X - Int(X);
   if X < 0 then
     X := X + 1;
   return X;

[edit] See also