glLightModel(3G) OpenGL Reference glLightModel(3G)
glLightModelf, glLightModeli, glLightModelfv, glLightModeliv - set the
lighting model parameters
void glLightModelf( GLenum pname,
GLfloat param )
void glLightModeli( GLenum pname,
GLint param )
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.
void glLightModelfv( GLenum pname,
const GLfloat *params )
void glLightModeliv( GLenum pname,
const GLint *params )
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.
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 [Toc] [Back]
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).
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glLightModel(3G) OpenGL Reference glLightModel(3G)
GL_LIGHT_MODEL_COLOR_CONTROL [Toc] [Back]
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 [Toc] [Back]
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 [Toc] [Back]
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
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glLightModel(3G) OpenGL Reference glLightModel(3G)
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
MACHINE DEPENDENCIES
On Octane2 VPro systems, glLightModel with GL_SEPARATE_SPECULAR_COLOR is
not compatible with fragment lighting. If fragment lighting is enabled,
it will override the separate specular color light model.
On Octane2 VPro systems, use of the texture q coordinate to achieve
projective texture effects will be processed on a per-vertex basis
instead of a per-pixel basis, unless the the texture matrix is set up to
be projective. (A projective texture matrix is defined to be one in
which any of the 13th, 14th or 15th elements is non-zero.) In addition,
if either two-sided lighting or fragment lighting is in effect,
projective texture effects will always be processed on a per-vertex
basis.
glLight, glMaterial
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