glLightModeliv function

Article
12/11/2020

The glLightModeliv function sets lighting model parameters.

Syntax

void WINAPI glLightModeliv(
         GLenum pname,
   const GLint  *params
);

Parameters

pname

A lighting model parameter. The following values are accepted.

Value	Meaning
GL_LIGHT_MODEL_AMBIENT	The params parameter contains four integer 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 default ambient scene intensity is (0.2, 0.2, 0.2, 1.0).
GL_LIGHT_MODEL_LOCAL_VIEWER	The params parameter is a single integer value that specifies how specular reflection angles are computed. If param 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 default is 0.
GL_LIGHT_MODEL_TWO_SIDE	The params parameter is a single integer value that specifies whether one-sided or two-sided lighting calculations are done for polygons. It has no effect on the lighting calculations for points, lines, or bitmaps. If param 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 default is 0.

params

A pointer to the value or values to which params will be set.

Return value

This function does not return a value.

Error codes

The following error codes can be retrieved by the glGetError function.

Name	Meaning
GL_INVALID_ENUM	pname was not an accepted value.
GL_INVALID_OPERATION	The function was called between a call to glBegin and the corresponding call to glEnd.

Remarks

The glLightModeliv function sets lighting model parameter. The pname parameter names a parameter and param gives the new value.the value or values of individual light source parameters.

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 zero 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 light's 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.

The following functions retrieve information related to the glLightModeliv function:

glGet with argument GL_LIGHT_MODEL_LOCAL_VIEWER

glGet with argument GL_LIGHT_MODEL_TWO_SIDE

glIsEnabled with argument GL_LIGHTING

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows 2000 Server [desktop apps only]
Header	Gl.h
Library	Opengl32.lib
DLL	Opengl32.dll