Light | Dark

glGetProgramiv

Name

glGetProgramiv — return a parameter from a program object

C Specification

void glGetProgramiv(GLuint program,
 GLenum pname,
 GLint *params);
 

Parameters

program

Specifies the program object to be queried.

pname

Specifies the object parameter. Accepted symbolic names are GL_DELETE_STATUS, GL_LINK_STATUS, GL_VALIDATE_STATUS, GL_INFO_LOG_LENGTH, GL_ATTACHED_SHADERS, GL_ACTIVE_ATTRIBUTES, GL_ACTIVE_ATTRIBUTE_MAX_LENGTH, GL_ACTIVE_UNIFORMS, GL_ACTIVE_UNIFORM_MAX_LENGTH.

params

Returns the requested object parameter.

Description

glGetProgramiv returns in params the value of a parameter for a specific program object. The following parameters are defined:

GL_DELETE_STATUS

params returns GL_TRUE if program is currently flagged for deletion, and GL_FALSE otherwise.

GL_LINK_STATUS

params returns GL_TRUE if the last link operation on program was successful, and GL_FALSE otherwise.

GL_VALIDATE_STATUS

params returns GL_TRUE or if the last validation operation on program was successful, and GL_FALSE otherwise.

GL_INFO_LOG_LENGTH

params returns the number of characters in the information log for program including the null termination character (i.e., the size of the character buffer required to store the information log). If program has no information log, a value of 0 is returned.

GL_ATTACHED_SHADERS

params returns the number of shader objects attached to program.

GL_ACTIVE_ATTRIBUTES

params returns the number of active attribute variables for program.

GL_ACTIVE_ATTRIBUTE_MAX_LENGTH

params returns the length of the longest active attribute name for program, including the null termination character (i.e., the size of the character buffer required to store the longest attribute name). If no active attributes exist, 0 is returned.

GL_ACTIVE_UNIFORMS

params returns the number of active uniform variables for program.

GL_ACTIVE_UNIFORM_MAX_LENGTH

params returns the length of the longest active uniform variable name for program, including the null termination character (i.e., the size of the character buffer required to store the longest uniform variable name). If no active uniform variables exist, 0 is returned.

Notes

If an error is generated, no change is made to the contents of params.

Errors

GL_INVALID_ENUM is generated if pname is not an accepted value.

GL_INVALID_VALUE is generated if program is not a value generated by OpenGL.

GL_INVALID_OPERATION is generated if program does not refer to a program object.

Associated Gets

glGetActiveAttrib with argument program

glGetActiveUniform with argument program

glGetAttachedShaders with argument program

glGetProgramInfoLog with argument program

glIsProgram

Examples

Retrieve uniform data after the shader has been compiled
// The index returned from these GLint functions gets passed to glEnableVertexAttribArray during rendering.
GLint position_attrib_index = glGetAttribLocation(program, "position"); // program is what is returned by glCreateProgram.
GLint texcoord_attrib_index = glGetAttribLocation(program, "texcoord");
GLint normal_attrib_index = glGetAttribLocation(program, "normal");
GLint color_attrib_index = glGetAttribLocation(program, "color");

glBindFragDataLocation(program, 0, "output_color"); // "output_color" is an output value in your vertex shader and an input value in your fragment shader.

GLint num_uniforms;
glGetProgramiv(program, GL_ACTIVE_UNIFORMS, &num_uniforms);
GLchar uniform_name[256];
GLsizei length;
GLint size;
GLenum type;
for (int i = 0; i < num_uniforms; i++)
{
    glGetActiveUniform(program, i, sizeof(uniform_name), &length, &size, &type, uniform_name);
    // ... save this uniform data so it can be used during rendering
}
Compile a program from a vertex shader and a fragment shader.
GLuint vshader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vshader, 1, &vertex_shader_source, NULL); // vertex_shader_source is a GLchar* containing glsl shader source code
glCompileShader(vshader);

GLint vertex_compiled;
glGetShaderiv(vshader, GL_COMPILE_STATUS, &vertex_compiled);
if (vertex_compiled != GL_TRUE)
{
    GLsizei log_length = 0;
    GLchar message[1024];
    glGetShaderInfoLog(vshader, 1024, &log_length, message);
    // Write the error to a log
}

GLuint fshader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fshader, 1, &fragment_shader_source, NULL); // fragment_shader_source is a GLchar* containing glsl shader source code
glCompileShader(fshader);

GLint fragment_compiled;
glGetShaderiv(fshader, GL_COMPILE_STATUS, &fragment_compiled);
if (fragment_compiled != GL_TRUE)
{
    GLsizei log_length = 0;
    GLchar message[1024];
    glGetShaderInfoLog(fshader, 1024, &log_length, message);
    // Write the error to a log
}

GLuint program = glCreateProgram();

glBindAttribLocation(program, 0, "position"); // The index passed into glBindAttribLocation is
glBindAttribLocation(program, 1, "texcoord"); // used by glEnableVertexAttribArray. "position"
glBindAttribLocation(program, 2, "normal");   // "texcoord" "normal" and "color" are the names of the
glBindAttribLocation(program, 3, "color");    // respective inputs in your fragment shader.

glAttachShader(program, vshader);
glAttachShader(program, fshader);
glLinkProgram(program);

GLint program_linked;
glGetProgramiv(program, GL_LINK_STATUS, &program_linked);
if (program_linked != GL_TRUE)
{
    GLsizei log_length = 0;
    GLchar message[1024];
    glGetProgramInfoLog(program, 1024, &log_length, message);
    // Write the error to a log
}
Think you can improve this page? Edit this page on GitHub.