NAME
	  glLightModelf, glLightModeli,	glLightModelfv,	glLightModeliv
	  - set	the lighting model parameters


     C SPECIFICATION
	  void glLightModelf( GLenum pname,
			      GLfloat param )
	  void glLightModeli( GLenum pname,
			      GLint param )


     PARAMETERS
	  pname	  Specifies a single-valued lighting model parameter.
		  GL_LIGHT_MODEL_LOCAL_VIEWER and
		  GL_LIGHT_MODEL_TWO_SIDE are accepted.

	  param	  Specifies the	value that param will be set to.

     C SPECIFICATION
	  void glLightModelfv( GLenum pname,
			       const GLfloat *params )
	  void glLightModeliv( GLenum pname,
			       const GLint *params )


     PARAMETERS
	  pname
	       Specifies a lighting model parameter.
	       GL_LIGHT_MODEL_AMBIENT, GL_LIGHT_MODEL_LOCAL_VIEWER,
	       and GL_LIGHT_MODEL_TWO_SIDE are accepted.

	  params
	       Specifies a pointer to the value	or values that params
	       will be set to.

     DESCRIPTION
	  glLightModel sets the	lighting model parameter.  pname names
	  a parameter and params gives the new value.  There are three
	  lighting model parameters:

	  GL_LIGHT_MODEL_AMBIENT
		    params contains four integer or floating-point
		    values that	specify	the ambient RGBA intensity of
		    the	entire scene.  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 scene intensity is (0.2, 0.2, 0.2, 1.0).

	  GL_LIGHT_MODEL_LOCAL_VIEWER
		    params is a	single integer or floating-point value
		    that specifies how specular	reflection angles are
		    computed.  If params is 0 (or 0.0),	specular
		    reflection angles take the view direction to be
		    parallel to	and in the direction of	the -z axis,
		    regardless of the location of the vertex in	eye
		    coordinates.  Otherwise, specular reflections are
		    computed from the origin of	the eye	coordinate
		    system.  The initial value is 0.

	  GL_LIGHT_MODEL_TWO_SIDE
		    params is a	single integer or floating-point value
		    that specifies whether one-	or two-sided lighting
		    calculations are done for polygons.	 It has	no
		    effect on the lighting calculations	for points,
		    lines, or bitmaps.	If params is 0 (or 0.0), one-
		    sided lighting is specified, and only the front
		    material parameters	are used in the	lighting
		    equation.  Otherwise, two-sided lighting is
		    specified.	In this	case, vertices of back-facing
		    polygons are lighted using the back	material
		    parameters,	and have their normals reversed	before
		    the	lighting equation is evaluated.	 Vertices of
		    front-facing polygons are always lighted using the
		    front material parameters, with no change to their
		    normals. The initial value is 0.

	  In RGBA mode,	the lighted color of a vertex is the sum of
	  the material emission	intensity, the product of the material
	  ambient reflectance and the lighting model full-scene
	  ambient intensity, and the contribution of each enabled
	  light	source.	 Each light source contributes the sum of
	  three	terms:	ambient, diffuse, and specular.	 The ambient
	  light	source contribution is the product of the material
	  ambient reflectance and the light's ambient intensity.  The
	  diffuse light	source contribution is the product of the
	  material diffuse reflectance,	the light's diffuse intensity,
	  and the dot product of the vertex's normal with the
	  normalized vector from the vertex to the light source.  The
	  specular light source	contribution is	the product of the
	  material specular reflectance, the light's specular
	  intensity, and the dot product of the	normalized vertex-to-
	  eye and vertex-to-light vectors, raised to the power of the
	  shininess of the material.  All three	light source
	  contributions	are attenuated equally based on	the distance
	  from the vertex to the light source and on light source
	  direction, spread exponent, and spread cutoff	angle.	All
	  dot products are replaced with 0 if they evaluate to a
	  negative value.

	  The alpha component of the resulting lighted color is	set to
	  the alpha value of the material diffuse reflectance.

	  In color index mode, the value of the	lighted	index of a
	  vertex ranges	from the ambient to the	specular values	passed
	  to glMaterial	using GL_COLOR_INDEXES.	 Diffuse and specular
	  coefficients,	computed with a	(.30, .59, .11)	weighting of
	  the lights' colors, the shininess of the material, and the
	  same reflection and attenuation equations as in the RGBA
	  case,	determine how much above ambient the resulting index
	  is.

     ERRORS
	  GL_INVALID_ENUM is generated if pname	is not an accepted
	  value.

	  GL_INVALID_OPERATION is generated if glLightModel is
	  executed between the execution of glBegin and	the
	  corresponding	execution of glEnd.

     ASSOCIATED	GETS
	  glGet	with argument GL_LIGHT_MODEL_AMBIENT
	  glGet	with argument GL_LIGHT_MODEL_LOCAL_VIEWER
	  glGet	with argument GL_LIGHT_MODEL_TWO_SIDE
	  glIsEnabled with argument GL_LIGHTING

     SEE ALSO
	  glLight, glMaterial