Linux Manual Pages

Free Software * Books

Source Code

Free Media

Linux

GLTEXENV

NAME
C SPECIFICATION
PARAMETERS
C SPECIFICATION
PARAMETERS
DESCRIPTION
NOTES
ASSOCIATED GETS
SEE ALSO

NAME

glTexEnvf, glTexEnvi, glTexEnvfv, glTexEnviv − set texture environment parameters

C SPECIFICATION

void glTexEnvf( GLenum target,

	GLenum pname,
	GLfloat param )

void glTexEnvi( GLenum target,

	GLenum pname,
	GLint param )

PARAMETERS

	target		Specifies a texture environment. Must be GL_TEXTURE_ENV.
	pname		Specifies the symbolic name of a single-valued texture environment parameter. Must be GL_TEXTURE_ENV_MODE.
	param		Specifies a single symbolic constant, one of GL_MODULATE, GL_DECAL, GL_BLEND, or GL_REPLACE.

C SPECIFICATION

void glTexEnvfv( GLenum target,
GLenum pname,

const GLfloat *params )

void glTexEnviv( GLenum target,

	GLenum pname,
	const GLint *params )

PARAMETERS

	target		Specifies a texture environment. Must be GL_TEXTURE_ENV.
	pname		Specifies the symbolic name of a texture environment parameter. Accepted values are GL_TEXTURE_ENV_MODE and GL_TEXTURE_ENV_COLOR.
	params		Specifies a pointer to a parameter array that contains either a single symbolic constant or an RGBA color.

DESCRIPTION

A texture environment specifies how texture values are interpreted when a fragment is textured. target must be GL_TEXTURE_ENV. pname can be either GL_TEXTURE_ENV_MODE or GL_TEXTURE_ENV_COLOR.

If pname is GL_TEXTURE_ENV_MODE, then params is (or points to) the symbolic name of a texture function. Four texture functions may be specified: GL_MODULATE, GL_DECAL, GL_BLEND, and GL_REPLACE.

A texture function acts on the fragment to be textured using the texture image value that applies to the fragment (see glTexParameter) and produces an RGBA color for that fragment. The following table shows how the RGBA color is produced for each of the three texture functions that can be chosen. $C$ is a triple of color values (RGB) and $A$ is the associated alpha value. RGBA values extracted from a texture image are in the range [0,1]. The subscript $f$ refers to the incoming fragment, the subscript $t$ to the texture image, the subscript $c$ to the texture environment color, and subscript $v$ indicates a value produced by the texture function.

A texture image can have up to four components per texture element (see glTexImage1D, glTexImage2D, glTexImage3D, glCopyTexImage1D, and glCopyTexImage2D). In a one-component image, $L sub t$ indicates that single component. A two-component image uses $L sub t$ and $A sub t$. A three-component image has only a color value, $C sub t$. A four-component image has both a color value $C sub t$ and an alpha value $A sub t$.

If pname is GL_TEXTURE_ENV_COLOR, params is a pointer to an array that holds an RGBA color consisting of four values. Integer color components are interpreted linearly such that the most positive integer maps to 1.0, and the most negative integer maps to -1.0. The values are clamped to the range [0,1] when they are specified. $C sub c$ takes these four values.

GL_TEXTURE_ENV_MODE defaults to GL_MODULATE and GL_TEXTURE_ENV_COLOR defaults to (0, 0, 0, 0).

NOTES

GL_REPLACE may only be used if the GL version is 1.1 or greater.

Internal formats other than 1, 2, 3, or 4 may only be used if the GL version is 1.1 or greater.

When the GL_ARB_multitexture extension is supported, glTexEnv controls the texture environment for the current active texture unit, selected by glActiveTextureARB. GL_INVALID_ENUM is generated when target or pname is not one of the accepted defined values, or when params should have a defined constant value (based on the value of pname) and does not.

GL_INVALID_OPERATION is generated if glTexEnv is executed between the execution of glBegin and the corresponding execution of glEnd.

ASSOCIATED GETS

glGetTexEnv

Opportunity

Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.

Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.

Free Software

Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.

Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.

Free Books

The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.

Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.

Education

Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.

Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.