The XOR texture is a very easy to generate texture that looks fine. However, it's so overused that it's not a good choice to use in in a demo or intro release. It isn't useful for games either, unless you want some fancy floor tiles. What it's useful for, is for testing a texture mapper you just wrote, in case you want to quickly test out a pattern without having to load an image file or write more complex texture generation code.

This is an extremely small article, but the XOR Texture just couldn't be left out in a series of texture generation articles.
 

The XOR Texture

The XOR texture is simply generated by xor-ing the x and y coordinate of the current pixel. The '^' operator in C++ is the XOR operator.

 

int main(int argc, char *argv[]) 
{ 
    screen(256, 256, 0, "The XOR Texture"); 
   
    for(int x = 0; x < w; x++) 
    for(int y = 0; y < h; y++) 
    {    
         Uint8 c = x ^ y; 
         pset(x, y, ColorRGB(c, c, c)); 
    } 
   
    redraw(); 
    sleep(); 
    return 0; 
}

Colors

You can also try the XOR texture with different colors, by using different value for R, G and B. For example:

 

int main(int argc, char *argv[])
{
    screen(256, 256, 0, "The XOR Texture");
  
    ColorRGB color;
    
    for(int x = 0; x < w; x++)
    for(int y = 0; y < h; y++)
    {   
         Uint8 c = (x ^ y);
         color.r = 255 - c;
         color.g = c;
         color.b = c % 128;
         pset(x, y, color);
    }
      
    redraw();
    sleep();
    return 0;
}

int main(int argc, char *argv[])
{
    screen(256, 256, 0, "The XOR Texture");
  
    ColorRGB color; 
      
    for(int x = 0; x < w; x++)
    for(int y = 0; y < h; y++)
    {   
         Uint8 c = (x ^ y);
         color = HSVtoRGB(ColorHSV(c, 255, 255));
         pset(x, y, color);
    }
  
    redraw();
    sleep();
    return 0;
}

AND and OR

The AND and the OR operator also generate a similar texture.

The XOR operator returns 1 if both bits are different:

XOR
Bit_a	Bit_b	Result
0	0	0
0	1	1
1	0	1
1	1	0

The AND operator, only returns 1 if both bits are 1 (bit a AND bit b are true)

AND
Bit_a	Bit_b	Result
0	0	0
0	1	0
1	0	0
1	1	1

The OR operator returns 1 if any or both of the bits are 1 (bit a OR bit b is true)

OR
Bit_a	Bit_b	Result
0	0	0
0	1	1
1	0	1
1	1	1

The AND operator is denoted '&' in C++, and the OR operator '|', replace the '^' operator with those to use the new operators. Here's the result of XOR, AND and OR respectively:



It makes sense that the AND texture is darker, because it returns 1 only in a single case. The OR texture is brighter, because it returns 1 very often. The sum of the XOR texture and the AND texture is the OR texture.
 

Conclusion

It was shown how easy it is to create a XOR texture, which makes the XOR texture useful to test if a texture renderer is working. However, it's not suitable for applications such as art or games.

Here, the XOR pattern was used as a 3D texture (x ^ y ^ z) to test if a planet texture renderer was working correctly: