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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 de- pends on the implementation, but at least eight lights are sup- ported. 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 sym- bolic names are GL_AMBIENT, GL_DIFFUSE, GL_SPECULAR, GL_POSI- TION, GL_SPOT_DIRECTION, GL_SPOT_EXPONENT, GL_SPOT_CUTOFF, GL_CONSTANT_ATTENUATION, GL_LINEAR_ATTENUATION , and GL_QUA- DRATIC_ATTENUATION. params Returns the requested data. DESCRIPTION glGetLight returns in params the value or values of a light source pa- rameter. 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 imple- mentation 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 val- ues representing the ambient intensity of the light source. Integer values, when requested, are lin- early mapped from the internal floating-point rep- resentation 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 val- ues representing the diffuse intensity of the light source. Integer values, when requested, are lin- early mapped from the internal floating-point rep- resentation 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_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 val- ues 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 posi- tive 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 unde- fined. 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 val- ues 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, un- less the modelview matrix was identity at the time glLight was called. The initial value is (0, 0, 1, 0). GL_SPOT_DIRECTION params returns three integer or floating-point val- ues representing the direction 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, un- less the modelview matrix was identity at the time glLight was called. Although spot direction is normalized before being used in the lighting equa- tion, the returned values are the transformed ver- sions of the specified values prior to normaliza- tion. 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 rep- resentation 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-re- lated) attenuation of the light. An integer value, when requested, is computed by rounding the inter- nal 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 com- puted by rounding the internal floating-point rep- resentation to the nearest 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 com- puted by rounding the internal floating-point rep- resentation 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 execution 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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