MirOS Manual: glGetLight(3), glGetLightfv(3), glGetLightiv(3)


GLGETLIGHT(3G)      UNIX Programmer's Manual       GLGETLIGHT(3G)

NAME

     glGetLightfv, glGetLightiv - return light source parameter
     values

C SPECIFICATION

     void glGetLightfv( GLenum light,
                        GLenum pname,
                        GLfloat *params )
     void glGetLightiv( GLenum light,
                        GLenum pname,
                        GLint *params )

PARAMETERS

     light   Specifies a light source. The number of possible
             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.
             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

     glGetLight returns in params the value or values of a light
     source parameter. light names the light and is a symbolic
     name of the form GL_LIGHTi for 0 ≤ i < GL_MAX_LIGHTS, where
     GL_MAX_LIGHTS is an implementation dependent constant that
     is greater than or equal to eight. pname specifies one of
     ten 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 light source.
                         Integer values, when requested, are
                         linearly mapped from the internal
                         floating-point representation such that
                         1.0 maps to the most positive represent-
                         able 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

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                         initial value is (0, 0, 0, 1).

     GL_DIFFUSE          params returns four integer or
                         floating-point values representing the
                         diffuse intensity of the light source.
                         Integer values, when requested, are
                         linearly mapped from the internal
                         floating-point representation such that
                         1.0 maps to the most positive represent-
                         able 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_LIGHT0 is (1, 1, 1,
                         1); for other 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 light source.
                         Integer values, when requested, are
                         linearly mapped from the internal
                         floating-point representation such that
                         1.0 maps to the most positive represent-
                         able 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_LIGHT0 is (1, 1, 1,
                         1); for other lights, the initial value
                         is (0, 0, 0, 0).

     GL_POSITION         params returns four integer or
                         floating-point values representing the
                         position of the 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 glLight,
                         unless the modelview matrix was identity
                         at the time glLight was called. The ini-
                         tial value is (0, 0, 1, 0).

     GL_SPOT_DIRECTION   params returns three integer or
                         floating-point values representing the
                         direction of the light source. Integer
                         values, when requested, are computed by
                         rounding the internal floating-point

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GLGETLIGHT(3G)      UNIX Programmer's Manual       GLGETLIGHT(3G)

                         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 glLight,
                         unless the modelview matrix was identity
                         at the time glLight was called. Although
                         spot direction is normalized before
                         being used in the lighting equation, the
                         returned values are the transformed ver-
                         sions 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 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_SPOT_CUTOFF      params returns a single integer or
                         floating-point value representing the
                         spot cutoff angle of the light. An
                         integer value, when requested, is com-
                         puted by rounding the internal
                         floating-point representation to the
                         nearest integer. The initial value is
                         180.

     GL_CONSTANT_ATTENUATION
                         params returns a single integer or
                         floating-point value representing the
                         constant (not distance-related) attenua-
                         tion of the light. An integer value,
                         when requested, is computed by rounding
                         the internal floating-point representa-
                         tion to the nearest integer. The initial
                         value is 1.

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

     GL_QUADRATIC_ATTENUATION
                         params returns a single integer or
                         floating-point value representing the

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GLGETLIGHT(3G)      UNIX Programmer's Manual       GLGETLIGHT(3G)

                         quadratic attenuation of the light. An
                         integer value, when requested, is com-
                         puted by rounding the internal
                         floating-point representation to the
                         nearest integer. The initial value is 0.

NOTES

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

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

ERRORS

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

     GL_INVALID_OPERATION is generated if glGetLight is executed
     between the execution of glBegin and the corresponding exe-
     cution of glEnd.

SEE ALSO

     glLight(3G)

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