glLightModel, glLightModelf, glLightModeli, glLightModelfv, glLightMod‐
eliv - set the lighting model parameters
GLfloat param ); void glLightModeli(
GLint param );
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. Specifies the value that param
will be set to.
const GLfloat *params ); void glLightModeliv(
const GLint *params );
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. Specifies a pointer to the value
or values that params will be set to.
DESCRIPTIONglLightModel() sets the lighting model parameter. pname names a param‐
eter and params gives the new value. There are three lighting model
parameters: 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 float‐
ing-point values are clamped. The initial ambient scene intensity is
(0.2, 0.2, 0.2, 1.0). 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_SEPA‐
RATE_SPECULAR_COLOR specifies that the specular color computation of
lighting be stored separately from the remainder of the lighting compu‐
tation. The specular color is summed into the generated fragment's
color after the application of texture mapping (if enabled). The ini‐
tial value is GL_SINGLE_COLOR. 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. params is a single integer or float‐
ing-point value that specifies whether one- or two-sided lighting cal‐
culations are done for polygons. It has no effect on the lighting cal‐
culations 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 speci‐
fied. 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 normal‐
ized 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 contri‐
butions 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 eval‐
uate 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.
GL_LIGHT_MODEL_COLOR_CONTROL is available only if the GL version is 1.2
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 GETSglGet() 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 ALSOglLight(3), glMaterial(3)glLightModel(3G)