NAME
	  glLightf, glLighti, glLightfv, glLightiv - 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 0 < i < GL_MAX_LIGHTS.

	  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	0 < i <	GL_MAX_LIGHTS.

	  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 0 <	i < GL_MAX_LIGHTS.  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, 0).

	  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, 0).

	  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
			      inverse of the modelview matrix when
			      glLight is called	(just as if it were a
			      normal), 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