Gl.GetLightfv (gb.opengl)

Return light source parameter values.

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 $\mathit{i}$ where $\mathit{i}$ ranges from 0 to the value of Gl.MAX_LIGHTS - 1.

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

Gl.GetLight 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.LIGHT $\mathit{i}$ where i ranges from 0 to the value of Gl.MAX_LIGHTS - 1. 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 representable integer value, and $-1.0$ maps to the most negative representable integer value. If the internal value is outside the range $\left.[/-1,1\right]$, 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 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 $\left.[/-1,1\right]$, 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 representable integer value, and $-1.0$ maps to the most negative representable integer value. If the internal value is outside the range $\left.[/-1,1\right]$, 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 Gl.Light, unless the modelview matrix was identity at the time Gl.Light 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 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 Gl.Light, unless the modelview matrix was identity at the time Gl.Light was called. Although spot direction is normalized before being used in the lighting equation, the returned values are the transformed versions of the specified values prior to normalization. The initial value is $\left(0,0,-1\right)$.

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 computed 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) attenuation 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 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 computed by rounding the internal floating-point representation to the nearest integer. The initial value is 0.

Notes

It is always the case that Gl.LIGHT $\mathit{i}$ = Gl.LIGHT0 + $\mathit{i}$.

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 Gl.GetLight is executed between the execution of Gl.Begin and the corresponding execution of Gl.End.

See also

See original documentation on OpenGL website