Index for Section 3G

Alphabetical listing for G

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glLightModel(3G)
NAME
  glLightModel, glLightModelf, glLightModeli, glLightModelfv, glLightModeliv
  - set the lighting model parameters

SYNOPSIS
  void glLightModelf(
	  GLenum pname,
	  GLfloat param );

  void glLightModeli(
	  GLenum pname,
	  GLint param );

PARAMETERS
  pname
      Specifies a single-valued lighting model parameter.
      GL_LIGHT_MODEL_LOCAL_VIEWER, GL_LIGHT_MODEL_COLOR_CONTROL, and
      GL_LIGHT_MODEL_TWO_SIDE are accepted.

  param
      Specifies the value that param will be set to.

SYNOPSIS
  void glLightModelfv(
	  GLenum pname,
	  const GLfloat *params );

  void glLightModeliv(
	  GLenum pname,
	  const GLint *params );

PARAMETERS
  pname
      Specifies a lighting model parameter.  GL_LIGHT_MODEL_AMBIENT,
      GL_LIGHT_MODEL_COLOR_CONTROL, GL_LIGHT_MODEL_LOCAL_VIEWER, and
      GL_LIGHT_MODEL_TWO_SIDE are accepted.

  params
      Specifies a pointer to the value or values that params will be set to.

DESCRIPTION
  glLightModel() sets the lighting model parameter.  pname names a parameter
  and params gives the new value. There are three lighting model parameters:

  GL_LIGHT_MODEL_AMBIENT
      params contains four integer or floating-point values that specify the
      ambient RGBA intensity of the entire scene. Integer values are mapped
      linearly such that the most positive representable value maps to 1.0,
      and the most negative representable value maps to -1.0. Floating-point
      values are mapped directly. Neither integer nor floating-point values
      are clamped.  The initial ambient scene intensity is (0.2, 0.2, 0.2,
      1.0).

  GL_LIGHT_MODEL_COLOR_CONTROL
      params must be either GL_SEPARATE_SPECULAR_COLOR or GL_SINGLE_COLOR.
      GL_SINGLE_COLOR specifies that a single color is generated from the
      lighting computation for a vertex.  GL_SEPARATE_SPECULAR_COLOR
      specifies that the specular color computation of lighting be stored
      separately from the remainder of the lighting computation.  The
      specular color is summed into the generated fragment's color after the
      application of texture mapping (if enabled).  The initial value is
      GL_SINGLE_COLOR.

  GL_LIGHT_MODEL_LOCAL_VIEWER
      params is a single integer or floating-point value that specifies how
      specular reflection angles are computed. If params is 0 (or 0.0),
      specular reflection angles take the view direction to be parallel to
      and in the direction of the -z axis, regardless of the location of the
      vertex in eye coordinates. Otherwise, specular reflections are computed
      from the origin of the eye coordinate system. The initial value is 0.

  GL_LIGHT_MODEL_TWO_SIDE
      params is a single integer or floating-point value that specifies
      whether one- or two-sided lighting calculations are done for polygons.
      It has no effect on the lighting calculations for points, lines, or
      bitmaps.	If params is 0 (or 0.0), one-sided lighting is specified, and
      only the front material parameters are used in the lighting equation.
      Otherwise, two-sided lighting is specified.  In this case, vertices of
      back-facing polygons are lighted using the back material parameters,
      and have their normals reversed before the lighting equation is
      evaluated. Vertices of front-facing polygons are always lighted using
      the front material parameters, with no change to their normals. The
      initial value is 0.

  In RGBA mode, the lighted color of a vertex is the sum of the material
  emission intensity, the product of the material ambient reflectance and the
  lighting model full-scene ambient intensity, and the contribution of each
  enabled light source. Each light source contributes the sum of three terms:
  ambient, diffuse, and specular. The ambient light source contribution is
  the product of the material ambient reflectance and the light's ambient
  intensity.  The diffuse light source contribution is the product of the
  material diffuse reflectance, the light's diffuse intensity, and the dot
  product of the vertex's normal with the normalized vector from the vertex
  to the light source. The specular light source contribution is the product
  of the material specular reflectance, the light's specular intensity, and
  the dot product of the normalized vertex-to-eye and vertex-to-light
  vectors, raised to the power of the shininess of the material. All three
  light source contributions are attenuated equally based on the distance
  from the vertex to the light source and on light source direction, spread
  exponent, and spread cutoff angle. All dot products are replaced with 0 if
  they evaluate to a negative value.

  The alpha component of the resulting lighted color is set to the alpha
  value of the material diffuse reflectance.

  In color index mode, the value of the lighted index of a vertex ranges from
  the ambient to the specular values passed to glMaterial() using
  GL_COLOR_INDEXES. Diffuse and specular coefficients, computed with a (.30,
  .59, .11) weighting of the lights' colors, the shininess of the material,
  and the same reflection and attenuation equations as in the RGBA case,
  determine how much above ambient the resulting index is.

NOTES
  GL_LIGHT_MODEL_COLOR_CONTROL is available only if the GL version is 1.2 or
  greater.

ERRORS
  GL_INVALID_ENUM is generated if pname is not an accepted value.

  GL_INVALID_ENUM is generated if pname is GL_LIGHT_MODEL_COLOR_CONTROL and
  params is not one of GL_SINGLE_COLOR or GL_SEPARATE_SPECULAR_COLOR.

  GL_INVALID_OPERATION is generated if glLightModel() is executed between the
  execution of glBegin() and the corresponding execution of glEnd().

ASSOCIATED GETS
       glGet() with argument GL_LIGHT_MODEL_AMBIENT
       glGet() with argument GL_LIGHT_MODEL_COLOR_CONTROL
       glGet() with argument GL_LIGHT_MODEL_LOCAL_VIEWER
       glGet() with argument GL_LIGHT_MODEL_TWO_SIDE
       glIsEnabled() with argument GL_LIGHTING

SEE ALSO
  glLight(3), glMaterial(3)

Index for Section 3G

Alphabetical listing for G

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