glGetFragmentLight(3G)	       OpenGL Reference		glGetFragmentLight(3G)

NAME    [Toc]    [Back]

     glGetFragmentLightfvSGIX, glGetFragmentLightivSGIX	- return fragment
     light source parameter values

C SPECIFICATION    [Toc]    [Back]

     void glGetFragmentLightfvSGIX( GLenum light,
				    GLenum pname,
				    GLfloat *params )
     void glGetFragmentLightivSGIX( GLenum light,
				    GLenum pname,
				    GLint *params )

PARAMETERS    [Toc]    [Back]

     light   Specifies a fragment light	source.	 The number of possible
	     fragment lights depends on	the implementation.  They are
	     identified	by symbolic names of the form GL_FRAGMENT_LIGHTi_SGIX
	     where 0 < i < GL_MAX_FRAGMENT_LIGHTS_SGIX.

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

     params  Returns the requested data.

DESCRIPTION    [Toc]    [Back]

     glGetFragmentLight	returns	in params the value or values of a fragment
     light source parameter.  light names the fragment light and is a symbolic
     name of the form GL_FRAGMENT_LIGHTi_SGIX for 0 < i	<
     GL_MAX_FRAGMENT_LIGHTS_SGIX, where	GL_MAX_FRAGMENT_LIGHTS_SGIX is an
     implementation dependent constant.	 pname specifies one of	ten fragment
     light source parameters, again by symbolic	name.

     The following parameters are defined:

     GL_AMBIENT		 params	returns	four integer or	floating-point values
			 representing the ambient intensity of the fragment
			 light source.	Integer	values,	when requested,	are
			 linearly mapped from the internal floating-point
			 representation	such that 1.0 maps to the most
			 positive representable	integer	value, and -1.0	maps
			 to the	most negative representable integer value.  If
			 the internal value is outside the range [-1, 1], the
			 corresponding integer return value is undefined. The
			 initial value is (0, 0, 0, 1).

     GL_DIFFUSE		 params	returns	four integer or	floating-point values
			 representing the diffuse intensity of the fragment
			 light source.	Integer	values,	when requested,	are



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glGetFragmentLight(3G)	       OpenGL Reference		glGetFragmentLight(3G)



			 linearly mapped from the internal floating-point
			 representation	such that 1.0 maps to the most
			 positive representable	integer	value, and -1.0	maps
			 to the	most negative representable integer value.  If
			 the internal value is outside the range [-1, 1], the
			 corresponding integer return value is undefined. The
			 initial value for GL_FRAGMENT_LIGHT0_SGIX is (1, 1,
			 1, 1);	for other fragment lights, the initial value
			 is (0,	0, 0, 0).

     GL_SPECULAR	 params	returns	four integer or	floating-point values
			 representing the specular intensity of	the fragment
			 light source.	Integer	values,	when requested,	are
			 linearly mapped from the internal floating-point
			 representation	such that 1.0 maps to the most
			 positive representable	integer	value, and -1.0	maps
			 to the	most negative representable integer value.  If
			 the internal value is outside the range [-1, 1], the
			 corresponding integer return value is undefined. The
			 initial value for GL_FRAGMENT_LIGHT0_SGIX is (1, 1,
			 1, 1);	for other fragment lights, the initial value
			 is (0,	0, 0, 0).

     GL_POSITION	 params	returns	four integer or	floating-point values
			 representing the position of the fragment light
			 source.  Integer values, when requested, are computed
			 by rounding the internal floating-point values	to the
			 nearest integer value.	 The returned values are those
			 maintained in eye coordinates.	 They will not be
			 equal to the values specified using glFragmentLight,
			 unless	the modelview matrix was identity at the time
			 glFragmentLight was called. The initial value is (0,
			 0, 1, 0).

     GL_SPOT_DIRECTION	 params	returns	three integer or floating-point	values
			 representing the direction of the fragment light
			 source.  Integer values, when requested, are computed
			 by rounding the internal floating-point values	to the
			 nearest integer value.	 The returned values are those
			 maintained in eye coordinates.	 They will not be
			 equal to the values specified using glFragmentLight,
			 unless	the modelview matrix was identity at the time
			 glFragmentLight was called.  Although spot direction
			 is normalized before being used in the	fragment
			 lighting equation, the	returned values	are the
			 transformed versions of the specified values prior to
			 normalization.	The initial value is (0, 0, -1).

     GL_SPOT_EXPONENT	 params	returns	a single integer or floating-point
			 value representing the	spot exponent of the fragment
			 light.	 An integer value, when	requested, is computed
			 by rounding the internal floating-point



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glGetFragmentLight(3G)	       OpenGL Reference		glGetFragmentLight(3G)



			 representation	to the nearest integer.	The initial
			 value is 0.

     GL_SPOT_CUTOFF	 params	returns	a single integer or floating-point
			 value representing the	spot cutoff angle of the
			 fragment light.  An integer value, when requested, is
			 computed by rounding the internal floating-point
			 representation	to the nearest integer.	The initial
			 value is 180.

     GL_CONSTANT_ATTENUATION    [Toc]    [Back]
			 params	returns	a single integer or floating-point
			 value representing the	constant (not distancerelated)
 attenuation of the fragment light.  An
			 integer value,	when requested,	is computed by
			 rounding the internal floating-point representation
			 to the	nearest	integer. The initial value is 1.

     GL_LINEAR_ATTENUATION    [Toc]    [Back]
			 params	returns	a single integer or floating-point
			 value representing the	linear attenuation of the
			 fragment light.  An integer value, when requested, is
			 computed by rounding the internal floating-point
			 representation	to the nearest integer.	The initial
			 value is 0.

     GL_QUADRATIC_ATTENUATION    [Toc]    [Back]
			 params	returns	a single integer or floating-point
			 value representing the	quadratic attenuation of the
			 fragment light.  An integer value, when requested, is
			 computed by rounding the internal floating-point
			 representation	to the nearest integer.	The initial
			 value is 0.

NOTES    [Toc]    [Back]

     It	is always the case that	GL_FRAGMENT_LIGHTi_SGIX	=
     GL_FRAGMENT_LIGHT0_SGIX + i.

     If	an error is generated, no change is made to the	contents of params.

ERRORS    [Toc]    [Back]

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

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


MACHINE	DEPENDENCIES
     The SGIX_fragment_lighting	extension is supported only on Octane2 VPro
     systems.




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glGetFragmentLight(3G)	       OpenGL Reference		glGetFragmentLight(3G)

SEE ALSO    [Toc]    [Back]

     glFragmentLight


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