Lighting

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:
  • Automaticdefault lighting schemes
    Noneno 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:

Introduced in 1988
 (1.0)
 |
Updated in 2007
 (6.0)
2014
 (10.0)
2020
 (12.1)