How shadow colours are chosen

A shadow is not the base colour multiplied by grey. The tool asks what the surface looks like once the key light is gone and only fill light remains. The shadow starts from that surface's own colour.

Lightness, hue, and saturation

Lightness drops in proportion to the sampled colour. A dark cloth is not pushed toward black by a fixed amount, so it does not collapse into a black mass. A dark material loses saturation in shadow rather than gaining it.

Hue moves only in the direction the fill light pulls it, and only within a set limit. It does not travel past the anchor colour. A vivid colour resists that move and keeps more of itself.

Saturation stays inside what the display can show at the new lightness, which is what keeps the shadow from dying into grey. Skin that is nearly white still gains saturation in shadow.

The sampled base colour itself is never replaced. A white or grey sample has no hue of its own, so the calculation borrows a stable hue from the material type and leaves the reported base colour as it was read.

Why the border is warmer than the shadow inside it

The band between the lit side and the shadow is calculated apart from the shadow core. Light wraps into that band, and warm bounce reaches it more. The border is often warmer and more colourful than the shadow inside it. It is always darker than the lit surface.

Material type

The material type chooses how the surface takes fill light. Types do not each carry a hand-built palette. Only the part that differs is overridden.

• Skin and teeth take light in and send it back out. More light remains in the shadow, and the direction is warm.
• Cloth keeps the shadow more colourful and uses a wider range of anchor colour.
• Metal takes the ambient colour strongly and keeps less of its own.
• Glass and gemstones, and other surfaces light passes through, keep more ambient light and more light in the deep shadow.
• A surface that emits light keeps the most light and moves hue the least.
• Other opaque materials use the default for an opaque surface that is not metal.

Automatic detection is a guess from the material name and the colour. Change the material type at the top of the window when the guess is wrong.

Which control changes what

What you want to change	Control	Result
How bright the primary shadow is	Fill-Light Reduction	How much fill light remains in the shadow. Higher is darker.
How bright the deep shadow is	Deep Fill-Light Reduction	Brightness only in more occluded places, such as creases.
Which way the shadow hue leans	Warm / Cool Bias	Whether the shadow follows warm bounce or cool ambient. Lightness stays put.
Saturation	Saturation	Mutes or strengthens them.

Only the fill-light reduction controls change shadow lightness. A warmer shadow is not a darker one.

To edit the lights themselves, use the Advanced tab. A material type plus the controls above is enough for an ordinary result.