glUseProgram — Installs a program object as part of current rendering state
void glUseProgram( | GLuint | program); |
programSpecifies the handle of the program object whose executables are to be used as part of current rendering state.
glUseProgram installs the program
object specified by program as part of
current rendering state. One or more executables are created in
a program object by successfully attaching shader objects to it
with
glAttachShader,
successfully compiling the shader objects with
glCompileShader,
and successfully linking the program object with
glLinkProgram.
A program object will contain an executable that will run
on the vertex processor if it contains one or more shader
objects of type GL_VERTEX_SHADER that have
been successfully compiled and linked. Similarly, a program
object will contain an executable that will run on the fragment
processor if it contains one or more shader objects of type
GL_FRAGMENT_SHADER that have been
successfully compiled and linked.
Successfully installing an executable on a programmable processor will cause the corresponding fixed functionality of OpenGL to be disabled. Specifically, if an executable is installed on the vertex processor, the OpenGL fixed functionality will be disabled as follows.
The modelview matrix is not applied to vertex coordinates.
The projection matrix is not applied to vertex coordinates.
The texture matrices are not applied to texture coordinates.
Normals are not transformed to eye coordinates.
Normals are not rescaled or normalized.
Normalization of
GL_AUTO_NORMAL evaluated normals is
not performed.
Texture coordinates are not generated automatically.
Per-vertex lighting is not performed.
Color material computations are not performed.
Color index lighting is not performed.
This list also applies when setting the current raster position.
The executable that is installed on the vertex processor is expected to implement any or all of the desired functionality from the preceding list. Similarly, if an executable is installed on the fragment processor, the OpenGL fixed functionality will be disabled as follows.
Texture environment and texture functions are not applied.
Texture application is not applied.
Color sum is not applied.
Fog is not applied.
Again, the fragment shader that is installed is expected to implement any or all of the desired functionality from the preceding list.
While a program object is in use, applications are free to
modify attached shader objects, compile attached shader objects,
attach additional shader objects, and detach or delete shader
objects. None of these operations will affect the executables
that are part of the current state. However, relinking the
program object that is currently in use will install the program
object as part of the current rendering state if the link
operation was successful (see
glLinkProgram
). If the program object currently in use is relinked
unsuccessfully, its link status will be set to
GL_FALSE, but the executables and
associated state will remain part of the current state until a
subsequent call to glUseProgram removes it
from use. After it is removed from use, it cannot be made part
of current state until it has been successfully relinked.
If program contains shader objects
of type GL_VERTEX_SHADER but it does not
contain shader objects of type
GL_FRAGMENT_SHADER, an executable will be
installed on the vertex processor, but fixed functionality will
be used for fragment processing. Similarly, if
program contains shader objects of type
GL_FRAGMENT_SHADER but it does not contain
shader objects of type GL_VERTEX_SHADER, an
executable will be installed on the fragment processor, but
fixed functionality will be used for vertex processing. If
program is 0, the programmable processors
will be disabled, and fixed functionality will be used for both
vertex and fragment processing.
glUseProgram is available only if the
GL version is 2.0 or greater.
While a program object is in use, the state that controls the disabled fixed functionality may also be updated using the normal OpenGL calls.
Like display lists and texture objects, the name space for program objects may be shared across a set of contexts, as long as the server sides of the contexts share the same address space. If the name space is shared across contexts, any attached objects and the data associated with those attached objects are shared as well.
Applications are responsible for providing the synchronization across API calls when objects are accessed from different execution threads.
GL_INVALID_VALUE is generated if
program is neither 0 nor a value
generated by OpenGL.
GL_INVALID_OPERATION is generated if
program is not a program object.
GL_INVALID_OPERATION is generated if
program could not be made part of current
state.
GL_INVALID_OPERATION is generated if
glUseProgram is executed between the
execution of
glBegin
and the corresponding execution of
glEnd.
glGet
with the argument GL_CURRENT_PROGRAM
glGetActiveAttrib with a valid program object and the index of an active attribute variable
glGetActiveUniform with a valid program object and the index of an active uniform variable
glGetAttachedShaders with a valid program object
glGetAttribLocation with a valid program object and the name of an attribute variable
glGetProgram with a valid program object and the parameter to be queried
glGetProgramInfoLog with a valid program object
glGetUniform with a valid program object and the location of a uniform variable
glGetUniformLocation with a valid program object and the name of a uniform variable
gllAttachShader, glBindAttribLocation, glCompileShader, glCreateProgram, glDeleteProgram, glDetachShader, glLinkProgram, glUniform, glValidateProgram, glVertexAttrib
Copyright © 2003-2005 3Dlabs Inc. Ltd. This material may be distributed subject to the terms and conditions set forth in the Open Publication License, v 1.0, 8 June 1999. http://opencontent.org/openpub/.