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glLightModel(3G)
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glLightModel, glLightModelf, glLightModeli, glLightModelfv,
glLightModeliv - set the lighting model parameters
void glLightModelf(
GLenum pname,
GLfloat param ); void glLightModeli(
GLenum pname,
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.
void glLightModelfv(
GLenum pname,
const GLfloat *params ); void glLightModeliv(
GLenum pname,
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.
glLightModel() sets the lighting model parameter. pname
names a parameter 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 floating-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_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. 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 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 vertexto-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.
GL_LIGHT_MODEL_COLOR_CONTROL is available only if the GL
version is 1.2 or greater.
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().
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
glLight(3), glMaterial(3)
glLightModel(3G)
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