Why layers are drawn in gray

This is the idea the whole product is built on. Everything else follows from it.

A drawing is shape and shading. Color is separate.

When you draw a sphere, you are really doing two things at once: deciding its shape, and deciding which parts of it are bright and which are dark. The hue -- red, blue, gold -- is a third, independent decision.

A value-map keeps the first two and throws away the third. You draw in gray, where the gray is lightness: dark where the object is in shadow, bright where the light hits it. At generation time nfty keeps every pixel's brightness exactly as you drew it and injects a hue and a saturation.

Draw a sphere in gray once and it can be a red sphere, a blue sphere or a gold one, correctly shaded in each. Draw it in red and it is only ever red.

What this buys

Your art multiplies. A layer with two gray drawings and a wide hue range is not two options -- it is two shapes times however many colors nfty can tell apart, which is usually hundreds.

Your collection stays coherent. Every asset shares your shading and your shapes, so it reads as one collection rather than a pile of unrelated images, even while every asset is visibly different.

The output space is far bigger than the input. This is the reason a five-layer character made of thirteen drawings can produce nearly seven hundred thousand distinguishable assets.

What it costs

You are drawing in a way that is not quite drawing. A gray drawing looks unfinished, and it takes a little practice to judge shading without hue to help you. The editor's live preview exists precisely for this -- it shows the layer in a rolled color as you work, so you are never guessing.

When not to use it

When the colors are the art: a logo, a piece with several deliberate colors, a background with a photograph in it. Those are what the Custom kind is for. See The three kinds of layer.