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BUILT-IN MATHEMATICA SYMBOL
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:
-
Automatic default lighting schemes None no lighting {s1,s2,...} light sources 
, 
, ... - 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 
to 
{"Point",col,pt} spherical point light source at position pt {"Point",col,pt,att} point light with geometric attenuation att {"Spot",col,pt, 
}spotlight at pt aimed at the center with half-angle {"Spot",col,{pt,tar}, }spotlight at pt aimed at tar with half-angle {"Spot",col,{pt,tar},{ ,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->"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
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. directivesspecular reflection defined by Specularity directivesglow 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
are taken to yield parallel simulated light rays, so only the direction vector defined by 
is relevant, not its magnitude. » - Point light sources specified by
effectively yield light that emanates from the point pt but does not attenuate with distance. » 
yields light that attenuates like 
with distance 
. »
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. »
gives 
fall-off away from the center of the cone. »
gives 
attenuation with distance 
. »
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