GLGETLIGHT() GLGETLIGHT() 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 ) delim $$ 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_LIGHT$i$ 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_CON- STANT_ATTENUATION, GL_LINEAR_ATTENUATION , and GL_QUADRATIC_ATTENU- ATION. params Returns the requested data. DESCRIPTION glGetLight returns in params the value or values of a light source parame- ter. light names the light and is a symbolic name of the form GL_LIGHT$i$ for 0<=$i$<GL_MAX_LIGHTS, where GL_MAX_LIGHTS is an implementation depen- dent 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 representable inte- ger value, and -1.0 maps to the most negative repre- sentable integer value. If the internal value is out- side the range [-1, 1], the corresponding integer re- turn 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 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 inte- ger value, and -1.0 maps to the most negative repre- sentable integer value. If the internal value is out- side the range [-1, 1], the corresponding integer re- turn value is undefined. The initial value for GL_LIGHT0 is (1, 1, 1, 1); for other lights, the ini- tial 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 representable integer value, and -1.0 maps to the most negative rep- resentable 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 ini- tial 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. Inte- ger values, when requested, are computed by rounding the internal floating-point values to the nearest inte- ger 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 trans- formed versions of the specified values prior to nor- malization. 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 inte- ger 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 computed by rounding the internal floating-point representation to the near- est integer. The initial value is 180. GL_CONSTANT_ATTENUATION params returns a single integer or floating-point value representing the constant (not distance-related) atten- uation 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 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 computed by rounding the internal floating-point representation to the near- est integer. The initial value is 0. GL_QUADRATIC_ATTENUATION params returns a single integer or floating-point value representing the quadratic attenuation of the light. An integer value, when requested, is computed by round- ing the internal floating-point representation to the nearest integer. The initial value is 0. NOTES It is always the case that GL_LIGHT$i$ = 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 ex- ecution of glBegin and the corresponding execution of glEnd. SEE ALSO glLight GLGETLIGHT()
NAME | C SPECIFICATION | PARAMETERS | DESCRIPTION | NOTES | ERRORS | SEE ALSO
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