The Comparison node offers you the ability to use a logical comparison operator as a way to combine textures. The node takes four inputs: the first two inputs are the textures for comparison. The second two inputs are the result of the comparison. (Figure 1).


Figure 1: The various input pins for the Comparison node: (1) Input 1, (2) Input 2, (3) If A<B, (4) If A>=B


This is a conditional Texture node for altering a given texture (input A) based on another texture (input B). In its simplest form, the Comparison node is used to select between two alternative textures at render time.


In the example below, the result will be black since inputs A and B are the same, and it evaluates to "true" for the second condition.