1991-2006 Silicon Graphics, Inc.

glMaterial

3G

glMaterial

specify material parameters for the lighting model

# C Specification

                    void glMaterialf
                    GLenum face
                    GLenum pname
                    GLfloat param

                    void glMateriali
                    GLenum face
                    GLenum pname
                    GLint param

## Parameters

`face`

- Specifies which face or faces are being updated. Must be one of `GL_FRONT`, `GL_BACK`, or `GL_FRONT_AND_BACK`.

`pname`

- Specifies the single-valued material parameter of the face or faces that is being updated. Must be `GL_SHININESS`.

`param`

- Specifies the value that parameter `GL_SHININESS` will be set to.

## C Specification

                    void glMaterialfv
                    GLenum face
                    GLenum pname
                    const GLfloat * params

                    void glMaterialiv
                    GLenum face
                    GLenum pname
                    const GLint * params

## Parameters

`face`

- Specifies which face or faces are being updated. Must be one of `GL_FRONT`, `GL_BACK`, or `GL_FRONT_AND_BACK`.

`pname`

- Specifies the material parameter of the face or faces that is being updated. Must be one of `GL_AMBIENT`, `GL_DIFFUSE`, `GL_SPECULAR`, `GL_EMISSION`, `GL_SHININESS`, `GL_AMBIENT_AND_DIFFUSE`, or `GL_COLOR_INDEXES`.

`params`

- Specifies a pointer to the value or values that `pname` will be set to.

## Description

`glMaterial` assigns values to material parameters. There are two matched sets of material parameters. One, the front-facing set, is used to shade points, lines, bitmaps, and all polygons (when two-sided lighting is disabled), or just front-facing polygons (when two-sided lighting is enabled). The other set, back-facing, is used to shade back-facing polygons only when two-sided lighting is enabled. Refer to the

glLightModel

reference page for details concerning one- and two-sided lighting calculations.

`glMaterial` takes three arguments. The first, `face`, specifies whether the `GL_FRONT` materials, the `GL_BACK` materials, or both `GL_FRONT_AND_BACK` materials will be modified. The second, `pname`, specifies which of several parameters in one or both sets will be modified. The third, `params`, specifies what value or values will be assigned to the specified parameter.

Material parameters are used in the lighting equation that is optionally applied to each vertex. The equation is discussed in the

glLightModel

reference page. The parameters that can be specified using `glMaterial`, and their interpretations by the lighting equation, are as follows:

`GL_AMBIENT`

- `params` contains four integer or floating-point values that specify the ambient RGBA reflectance of the material. 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 reflectance for both front- and back-facing materials is (0.2, 0.2, 0.2, 1.0).

`GL_DIFFUSE`

- `params` contains four integer or floating-point values that specify the diffuse RGBA reflectance of the material. 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 diffuse reflectance for both front- and back-facing materials is (0.8, 0.8, 0.8, 1.0).

`GL_SPECULAR`

- `params` contains four integer or floating-point values that specify the specular RGBA reflectance of the material. 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 specular reflectance for both front- and back-facing materials is (0, 0, 0, 1).

`GL_EMISSION`

- `params` contains four integer or floating-point values that specify the RGBA emitted light intensity of the material. 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 emission intensity for both front- and back-facing materials is (0, 0, 0, 1).

`GL_SHININESS`

- `params` is a single integer or floating-point value that specifies the RGBA specular exponent of the material. Integer and floating-point values are mapped directly. Only values in the range 0 128 are accepted. The initial specular exponent for both front- and back-facing materials is 0.

`GL_AMBIENT_AND_DIFFUSE`

- Equivalent to calling `glMaterial` twice with the same parameter values, once with `GL_AMBIENT` and once with `GL_DIFFUSE`.

`GL_COLOR_INDEXES`

- `params` contains three integer or floating-point values specifying the color indices for ambient, diffuse, and specular lighting. These three values, and `GL_SHININESS`, are the only material values used by the color index mode lighting equation. Refer to the

  glLightModel

  reference page for a discussion of color index lighting.

## Notes

The material parameters can be updated at any time. In particular, `glMaterial` can be called between a call to

glBegin

and the corresponding call to

glEnd

. If only a single material parameter is to be changed per vertex, however,

glColorMaterial

is preferred over `glMaterial` (see

glColorMaterial

).

While the ambient, diffuse, specular and emission material parameters all have alpha components, only the diffuse alpha component is used in the lighting computation.

## Errors

`GL_INVALID_ENUM` is generated if either `face` or `pname` is not an accepted value.

`GL_INVALID_VALUE` is generated if a specular exponent outside the range 0 128 is specified.

## Associated Gets

glGetMaterial

## See Also

glColorMaterial

,

glLight

,

glLightModel

## 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/.