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

glGetLightfv, glGetLightiv- return light source parameter values

voidglGetLightfv( GLenumlight, GLenumpname, GLfloat *params) voidglGetLightiv( GLenumlight, GLenumpname, GLint *params)

lightSpecifies 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 formGL_LIGHTi where 0 ≤ i <GL_MAX_LIGHTS.pnameSpecifies a light source parameter forlight. Accepted symbolic names areGL_AMBIENT,GL_DIFFUSE,GL_SPECULAR,GL_POSITION,GL_SPOT_DIRECTION,GL_SPOT_EXPONENT,GL_SPOT_CUTOFF,GL_CONSTANT_ATTENUATION,GL_LINEAR_ATTENUATION, andGL_QUADRATIC_ATTENUATION.paramsReturns the requested data.

glGetLightreturns inparamsthe value or values of a light source parameter.lightnames the light and is a symbolic name of the formGL_LIGHTi for 0 ≤ i <GL_MAX_LIGHTS, whereGL_MAX_LIGHTSis an implementation dependent constant that is greater than or equal to eight.pnamespecifies one of ten light source parameters, again by symbolic name. The following parameters are defined:GL_AMBIENTparamsreturns 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 MirBSD #10-current Printed 2021-12-07 1 GLGETLIGHT(3G) UNIX Programmer's Manual GLGETLIGHT(3G) initial value is (0, 0, 0, 1).GL_DIFFUSEparamsreturns 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 forGL_LIGHT0is (1, 1, 1, 1); for other lights, the initial value is (0, 0, 0, 0).GL_SPECULARparamsreturns 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 forGL_LIGHT0is (1, 1, 1, 1); for other lights, the initial value is (0, 0, 0, 0).GL_POSITIONparamsreturns 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 usingglLight, unless the modelview matrix was identity at the timeglLightwas called. The ini- tial value is (0, 0, 1, 0).GL_SPOT_DIRECTIONparamsreturns 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 MirBSD #10-current Printed 2021-12-07 2 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 usingglLight, unless the modelview matrix was identity at the timeglLightwas 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_EXPONENTparamsreturns 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_CUTOFFparamsreturns 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_ATTENUATIONparamsreturns 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_ATTENUATIONparamsreturns 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_ATTENUATIONparamsreturns a single integer or floating-point value representing the MirBSD #10-current Printed 2021-12-07 3 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.

It is always the case thatGL_LIGHTi =GL_LIGHT0+ i. If an error is generated, no change is made to the contents ofparams.

GL_INVALID_ENUMis generated iflightorpnameis not an accepted value.GL_INVALID_OPERATIONis generated ifglGetLightis executed between the execution ofglBeginand the corresponding exe- cution ofglEnd.

glLight(3G)MirBSD #10-current Printed 2021-12-07 4