Lighting

is an option for Graphics3D and related functions that specifies what simulated lighting to use in coloring 3D surfaces.

Details

The following settings can be given:

	Automatic	default lighting schemes
	None	no lighting
	{s₁,s₂,…}	light sources s₁, s₂, …
	"Standard"	colored light sources in default positions
	"Neutral"	white light sources in default positions
	"Accent"	a directional white light in default direction

Each light source can be of the following forms:

	{"Ambient",col}	uniform ambient light of color col
	{"Directional",col,pt}	directional light from pt to the center of the bounding box
	{"Directional",col,{pt₁,pt₂}}	directional light along the vector from pt₁ to pt₂
	{"Point",col,pt}	spherical point light source at position pt
	{"Point",col,pt,att}	point light with geometric attenuation att
	{"Spot",col,pt,α}	spotlight at pt aimed at the center with half-angle α
	{"Spot",col,{pt,tar},α}	spotlight at pt aimed at tar with half-angle α
	{"Spot",col,{pt,tar},{α,s},att}	spotlight with spot exponent s and attenuation att

Light source positions and aiming points can be specified as follows:

	{x,y,z}	explicit coordinates that move with the graphic
	Scaled[{x,y,z}]	scaled coordinates that move with the graphic
	ImageScaled[{x,y,z}]	coordinates fixed relative to the final displayed image

In ImageScaled[{x,y,z}], the and run from 0 to 1 across the width and height of the bounding box of the final displayed image. The coordinate runs orthogonal to the plane of the display, and is 0 at the back of the 3D region, and 1 at the front.
Coordinates specified in Scaled and ImageScaled will often not be between 0 and 1.
Lighting->Automatic uses ambient light together with four light sources fixed relative to the final displayed image. With the typical default setting ColorFunction->Automatic, colored light sources are used; if an explicit setting for ColorFunction is given, the light sources are taken to be white. »
Lighting->"Standard" always uses colored light sources in the default positions. »
Lighting->"Neutral" always uses white light sources in the default positions. »
Lighting can be specified globally for a 3D graphic by giving a Lighting option for Plot3D, Graphics3D, etc.
Lighting can be specified separately for particular objects in Graphics3D by giving a style option Style[obj,Lighting->spec]. »
In a list of graphics primitives and directives, the alternative form {…,g,Lighting->spec,g,…} defines lighting for objects that follow the lighting specification in the list. »
The final colors of 3D surfaces are determined by linearly adding RGB colors from three sources:

	diffuse reflection defined by RGBColor etc. directives
	specular reflection defined by Specularity directives
	glow defined by Glow directives

The setting for Lighting affects only colors associated with diffuse and specular reflection.
Diffuse reflection is taken to follow Lambert's law, with light effectively scattered equally in all directions from a surface.
Specular reflection effectively takes light to be scattered only close to the mirror‐reflection direction, as specified in the notes for Specularity.
Colors of light sources can be defined by RGBColor, Hue, or any other color specification.
Light sources with color specifications of the form {dcol,Specularity[scol]} are effectively taken to have colors dcol for purposes of diffuse reflection, and scol for purposes of specular reflection. »
Directional light sources specified by {"Directional",col,{pt₁,pt₂}} are taken to yield parallel simulated light rays, so only the direction vector defined by {pt₁,pt₂} is relevant, not its magnitude. »
Point light sources specified by {"Point",col,pt} effectively yield light that emanates from the point pt but does not attenuate with distance. »
{"Point",col,pt,{a,b,c}} yields light that attenuates like with distance . »
{"Spot",col,{pt,tar},α} yields the same light distribution as a point light source, except that it is restricted to a cone with direction from pt to tar, and with half-angle in radians. »
{"Spot",col,{pt,tar},{α,s}} gives fall-off away from the center of the cone. »
{"Spot",col,{pt,tar},{α,s},{a,b,c}} gives attenuation with distance . »

Examples

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Basic Examples (4)

Default lighting on gray specular sphere:

Neutral lighting on gray specular sphere:

Directional light from the top of the specular surface:

Specify lighting for each object:

Scope (24)

Lighting Specification (18)

Default lighting on a white surface:

Default lighting when ColorFunction is specified:

No lighting means diffuse or specular colors will not be visible:

Using Glow specifies pure color without interaction with lights:

Ambient light is uniformly applied to all the surfaces in the scene:

Ambient light gives overall lighting on the scene:

Directional light is specified by a color and a vector defined by two points:

Directional lights with different colors:

Directional lights with different directions:

Directional lights on a specular surface:

Specify a spherical point light source by a color and a position:

Point lights with different colors:

Point lights at various positions:

Point lights on specular surfaces:

Specify spotlight by position, target position, and half-angle:

Spotlights with different colors:

Spotlights from different positions:

Spotlights with different half-angles:

Spotlights on specular surfaces:

Lighting Positions (3)

Specify the light source position in the graphics coordinate system by default:

The light source moves with the graphic when the view point changes:

Specify the light position by a fraction of the graphics coordinates using Scaled:

The light source moves with the graphic when the view point changes:

Specify the light position in the view coordinate system using ImageScaled:

The light source position is always fixed relative to the view point:

Lighting Attenuation (3)

By default, point lights are not affected by the distance from an object:

Specify a point light that attenuates with respect to the distance:

Specify a point light that attenuates by the square of the distance:

By default, spotlights fall off sharply outside the cone:

Spotlights with different spot exponent has intensity :

Spotlight without attenuation:

Spotlight with linear attenuation:

Spotlight with quadratic attenuation:

Generalizations & Extensions (6)

Predefined colored lighting:

Predefined neutral lighting:

Specify lighting for each object:

Specify lighting within the graphics:

If not specified, the target direction is given toward the center of the objects:

Specify diffuse and specular colors separately for both objects and lights:

Applications (3)

Set up four white spheres on a plane:

Directional light:

Point light:

Spotlight:

Different light instruments at the corner points:

Build a scene with multiple objects and light sources:

Animate the spotlights:

Properties & Relations (9)

Surface color and lighting interact with each other:

Diffuse object and lighting colors can be exchanged and produce the same effect:

Specular object and lighting colors can be exchanged and produce the same effect:

Specularity gives mirror-like reflection:

The final color is a linear combination of all the surface colors as well as lighting:

Lighting follows the additive color model:

Directional light yields rays parallel to the specified direction:

Point light yields rays toward all the directions from the position:

A spotlight emits conic rays toward the specified direction:

Possible Issues (5)

The default lighting may not be suitable for light surface colors:

Neutral lighting can be used to reflect surface colors more naturally:

If a color function is given to a plot, then neutral lighting is used automatically:

Restore the default colored lighting:

Flat surfaces may show little or no reflection:

Some surface colors do not reflect certain colored lights:

A spotlight on a sphere may display a jagged boundary:

Increasing the spot exponent may reduce the effect:

Neat Examples (2)

Random light setups for ring models:

A simple light show:

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Lighting

Details

Examples

Basic Examples (4)