glLightModel man page on RedHat
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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 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.
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 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(), glMaterial()
COPYRIGHT
Copyright © 1991-2006 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 03/16/2013 GLLIGHTMODEL(3G)
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