The basic principle behind making an image specifically for conversion to a Normal map can be summarised by the following simple 'rule'; "white is height, black is back". Normal map converters don't understand 'context' they're not able to determine what a given tone of black « » grey « » white is meant to represent from a height and depth perspective; is a dark colour actual depth or just shadow or dark paint. To this end the aforementioned rule forms the basis upon which all Normal map templates should be made, that 'white' represent surfaces closest the viewer whilst are 'black' are farthest. In other words; 'white' tones protrude, 'black' recede. In this way pseudo three-dimensional structures can be represented simply from a collection of greyscale tones.

As discussed above the colours displayed in a Normal map determine the orientation of a pixel when displayed on-screen - "blue" usually represents up/down (depth), "green" left/right, "red" top/bottom. However, the red and green channels can be flipped depending on the peculiarities of a given game engine (or the tools used to convert the image to Normal map) which often result in materials appearing inverted in-game (generally noticeable because surface shading reverses - dark areas face towards light instead of away from it). The fix for this is to re-open the Normal map in an image-editor and 'invert' either the red or green channel as needed (rarely do both need to be inverted or the blue need to be touched).