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GLLIGHT(3G)				  OpenGL Manual 			      GLLIGHT(3G)

NAME
       glLight - set light source parameters

C SPECIFICATION
       void glLightf(GLenum light, GLenum pname, GLfloat param);

       void glLighti(GLenum light, GLenum pname, GLint param);

PARAMETERS
       light
	   Specifies a light. The number of lights depends on the implementation, but at least
	   eight lights are supported. They are identified by symbolic names of the form
	   GL_LIGHTi, where i ranges from 0 to the value of GL_MAX_LIGHTS - 1.

       pname
	   Specifies a single-valued light source parameter for light.	GL_SPOT_EXPONENT,
	   GL_SPOT_CUTOFF, GL_CONSTANT_ATTENUATION, GL_LINEAR_ATTENUATION, and
	   GL_QUADRATIC_ATTENUATION are accepted.

       param
	   Specifies the value that parameter pname of light source light will be set to.

C SPECIFICATION
       void glLightfv(GLenum light, GLenum pname, const GLfloat * params);

       void glLightiv(GLenum light, GLenum pname, const GLint * params);

PARAMETERS
       light
	   Specifies a light. The number of lights depends on the implementation, but at least
	   eight lights are supported. They are identified by symbolic names of the form
	   GL_LIGHTi, where i ranges from 0 to the value of GL_MAX_LIGHTS - 1.

       pname
	   Specifies a light source parameter for light.  GL_AMBIENT, GL_DIFFUSE, GL_SPECULAR,
	   GL_POSITION, GL_SPOT_CUTOFF, GL_SPOT_DIRECTION, GL_SPOT_EXPONENT,
	   GL_CONSTANT_ATTENUATION, GL_LINEAR_ATTENUATION, and GL_QUADRATIC_ATTENUATION are
	   accepted.

       params
	   Specifies a pointer to the value or values that parameter pname of light source light
	   will be set to.

DESCRIPTION
       glLight sets the values of individual light source parameters.  light names the light and
       is a symbolic name of the form GL_LIGHTi, where i ranges from 0 to the value of
       GL_MAX_LIGHTS - 1.  pname specifies one of ten light source parameters, again by symbolic
       name.  params is either a single value or a pointer to an array that contains the new
       values.

       To enable and disable lighting calculation, call glEnable() and glDisable() with argument
       GL_LIGHTING. Lighting is initially disabled. When it is enabled, light sources that are
       enabled contribute to the lighting calculation. Light source i is enabled and disabled
       using glEnable() and glDisable() with argument GL_LIGHTi.

       The ten light parameters are as follows:

       GL_AMBIENT
	   params contains four integer or floating-point values that specify the ambient RGBA
	   intensity of the light. Integer values are mapped linearly such that the most positive
	   representable value maps to 1.0, and the most negative representable value maps to
	   -1.0. Floating-point values are mapped directly. Neither integer nor floating-point
	   values are clamped. The initial ambient light intensity is (0, 0, 0, 1).

       GL_DIFFUSE
	   params contains four integer or floating-point values that specify the diffuse RGBA
	   intensity of the light. Integer values are mapped linearly such that the most positive
	   representable value maps to 1.0, and the most negative representable value maps to
	   -1.0. Floating-point values are mapped directly. Neither integer nor floating-point
	   values are clamped. The initial value for GL_LIGHT0 is (1, 1, 1, 1); for other lights,
	   the initial value is (0, 0, 0, 1).

       GL_SPECULAR
	   params contains four integer or floating-point values that specify the specular RGBA
	   intensity of the light. Integer values are mapped linearly such that the most positive
	   representable value maps to 1.0, and the most negative representable value maps to
	   -1.0. Floating-point values are mapped directly. Neither integer nor floating-point
	   values are clamped. The initial value for GL_LIGHT0 is (1, 1, 1, 1); for other lights,
	   the initial value is (0, 0, 0, 1).

       GL_POSITION
	   params contains four integer or floating-point values that specify the position of the
	   light in homogeneous object coordinates. Both integer and floating-point values are
	   mapped directly. Neither integer nor floating-point values are clamped.

	   The position is transformed by the modelview matrix when glLight is called (just as if
	   it were a point), and it is stored in eye coordinates. If the w component of the
	   position is 0, the light is treated as a directional source. Diffuse and specular
	   lighting calculations take the light's direction, but not its actual position, into
	   account, and attenuation is disabled. Otherwise, diffuse and specular lighting
	   calculations are based on the actual location of the light in eye coordinates, and
	   attenuation is enabled. The initial position is (0, 0, 1, 0); thus, the initial light
	   source is directional, parallel to, and in the direction of the - z axis.

       GL_SPOT_DIRECTION
	   params contains three integer or floating-point values that specify the direction of
	   the light in homogeneous object coordinates. Both integer and floating-point values
	   are mapped directly. Neither integer nor floating-point values are clamped.

	   The spot direction is transformed by the upper 3x3 of the modelview matrix when
	   glLight is called, and it is stored in eye coordinates. It is significant only when
	   GL_SPOT_CUTOFF is not 180, which it is initially. The initial direction is 0 0 -1.

       GL_SPOT_EXPONENT
	   params is a single integer or floating-point value that specifies the intensity
	   distribution of the light. Integer and floating-point values are mapped directly. Only
	   values in the range 0 128 are accepted.

	   Effective light intensity is attenuated by the cosine of the angle between the
	   direction of the light and the direction from the light to the vertex being lighted,
	   raised to the power of the spot exponent. Thus, higher spot exponents result in a more
	   focused light source, regardless of the spot cutoff angle (see GL_SPOT_CUTOFF, next
	   paragraph). The initial spot exponent is 0, resulting in uniform light distribution.

       GL_SPOT_CUTOFF
	   params is a single integer or floating-point value that specifies the maximum spread
	   angle of a light source. Integer and floating-point values are mapped directly. Only
	   values in the range 0 90 and the special value 180 are accepted. If the angle between
	   the direction of the light and the direction from the light to the vertex being
	   lighted is greater than the spot cutoff angle, the light is completely masked.
	   Otherwise, its intensity is controlled by the spot exponent and the attenuation
	   factors. The initial spot cutoff is 180, resulting in uniform light distribution.

       GL_CONSTANT_ATTENUATION

       GL_LINEAR_ATTENUATION

       GL_QUADRATIC_ATTENUATION
	   params is a single integer or floating-point value that specifies one of the three
	   light attenuation factors. Integer and floating-point values are mapped directly. Only
	   nonnegative values are accepted. If the light is positional, rather than directional,
	   its intensity is attenuated by the reciprocal of the sum of the constant factor, the
	   linear factor times the distance between the light and the vertex being lighted, and
	   the quadratic factor times the square of the same distance. The initial attenuation
	   factors are (1, 0, 0), resulting in no attenuation.

NOTES
       It is always the case that GL_LIGHTi = GL_LIGHT0 + i.

ERRORS
       GL_INVALID_ENUM is generated if either light or pname is not an accepted value.

       GL_INVALID_VALUE is generated if a spot exponent value is specified outside the range 0
       128, or if spot cutoff is specified outside the range 0 90 (except for the special value
       180), or if a negative attenuation factor is specified.

       GL_INVALID_OPERATION is generated if glLight is executed between the execution of
       glBegin() and the corresponding execution of glEnd().

ASSOCIATED GETS
       glGetLight()

       glIsEnabled() with argument GL_LIGHTING

SEE ALSO
       glColorMaterial(), glLightModel(), glMaterial()

COPYRIGHT
       Copyright (C) 1991-2006 Silicon Graphics, Inc. This document is licensed under the SGI
       Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.

AUTHORS
       opengl.org

opengl.org				    06/10/2014				      GLLIGHT(3G)
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