Index for Section 3G

Alphabetical listing for G

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glGetLight(3G)
NAME
  glGetLight, glGetLightfv, glGetLightiv - return light source parameter
  values

SYNOPSIS
  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 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 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 [-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 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_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 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
      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 versions 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 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_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 execution of glEnd().

SEE ALSO
  glLight(3)

Index for Section 3G

Alphabetical listing for G

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