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GLLIGHTMODEL()							GLLIGHTMODEL()

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

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

       delim $$

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

       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 ac-
	      cepted.

       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 parame-
       ter and params gives the	new value.  There are three lighting model pa-
       rameters:

       GL_LIGHT_MODEL_AMBIENT
		 params	contains four integer or  floating-point  values  that
		 specify  the ambient RGBA intensity of	the entire scene.  In-
		 teger values are mapped linearly such that the	most  positive
		 representable value maps to 1.0, and the most negative	repre-
		 sentable  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 spec-
		 ifies how specular reflection angles are computed.  If	params
		 is 0 (or 0.0),	specular reflection angles take	the  view  di-
		 rection  to  be  parallel  to	and in the direction of	the -z
		 axis, regardless of the location of the vertex	in eye coordi-
		 nates.	 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 spec-
		 ifies whether one- or	two-sided  lighting  calculations  are
		 done for polygons.  It	has no effect on the lighting calcula-
		 tions	for  points,  lines,  or  bitmaps.  If params is 0 (or
		 0.0), one-sided lighting is specified,	and only the front ma-
		 terial	parameters are used in the lighting equation.	Other-
		 wise,	two-sided  lighting  is	specified.  In this case, ver-
		 tices of back-facing polygons are lighted using the back  ma-
		 terial	parameters, and	have their normals reversed before the
		 lighting  equation  is	 evaluated.   Vertices of front-facing
		 polygons are always lighted using the front material  parame-
		 ters,	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 normal-
       ized vector from	the vertex to the light	source.	  The  specular	 light
       source  contribution  is	 the  product  of  the	material  specular re-
       flectance, 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 contri-
       butions 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

								GLLIGHTMODEL()

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