
GLLIGHTMODEL(3G) OpenGL Manual GLLIGHTMODEL(3G)
NAME
glLightModel  set the lighting model parameters
C SPECIFICATION
void glLightModelf(GLenum pname, GLfloat param);
void glLightModeli(GLenum pname, GLint param);
PARAMETERS
pname
Specifies a singlevalued 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.
C SPECIFICATION
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 floatingpoint 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. Floatingpoint values are mapped directly. Neither integer nor
floatingpoint 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 floatingpoint 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 floatingpoint value that specifies whether one or
twosided 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),
onesided lighting is specified, and only the front material parameters are used in
the lighting equation. Otherwise, twosided lighting is specified. In this case,
vertices of backfacing polygons are lighted using the back material parameters and
have their normals reversed before the lighting equation is evaluated. Vertices of
frontfacing 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 fullscene 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 vertextoeye and
vertextolight 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(), glMaterial()
COPYRIGHT
Copyright (C) 19912006 Silicon Graphics, Inc. This document is licensed under the SGI
Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.
AUTHORS
opengl.org
opengl.org 06/10/2014 GLLIGHTMODEL(3G) 
