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glBindBuffer

Name

glBindBuffer — bind a named buffer object

C Specification

void glBindBuffer(GLenum target,
GLuint buffer);

Parameters

target

Specifies the target to which the buffer object is bound. The symbolic constant must be GL_ARRAY_BUFFER or GL_ELEMENT_ARRAY_BUFFER.

buffer

Specifies the name of a buffer object.

Description

glBindBuffer lets you create or use a named buffer object. Calling glBindBuffer with target set to GL_ARRAY_BUFFER or GL_ELEMENT_ARRAY_BUFFER and buffer set to the name of the new buffer object binds the buffer object name to the target. When a buffer object is bound to a target, the previous binding for that target is automatically broken.

Buffer object names are unsigned integers. The value zero is reserved, but there is no default buffer object for each buffer object target. Instead, buffer set to zero effectively unbinds any buffer object previously bound, and restores client memory usage for that buffer object target. Buffer object names and the corresponding buffer object contents are local to the shared object space of the current GL rendering context.

You may use glGenBuffers to generate a set of new buffer object names.

The state of a buffer object immediately after it is first bound is a zero-sized memory buffer with GL_STATIC_DRAW usage.

While a non-zero buffer object name is bound, GL operations on the target to which it is bound affect the bound buffer object, and queries of the target to which it is bound return state from the bound buffer object. While buffer object name zero is bound, as in the initial state, attempts to modify or query state on the target to which it is bound generates an GL_INVALID_OPERATION error.

When vertex array pointer state is changed by a call to glVertexAttribPointer, the current buffer object binding (GL_ARRAY_BUFFER_BINDING) is copied into the corresponding client state for the vertex attrib array being changed, one of the indexed GL_VERTEX_ATTRIB_ARRAY_BUFFER_BINDINGs. While a non-zero buffer object is bound to the GL_ARRAY_BUFFER target, the vertex array pointer parameter that is traditionally interpreted as a pointer to client-side memory is instead interpreted as an offset within the buffer object measured in basic machine units.

While a non-zero buffer object is bound to the GL_ELEMENT_ARRAY_BUFFER target, the indices parameter of glDrawElements that is traditionally interpreted as a pointer to client-side memory is instead interpreted as an offset within the buffer object measured in basic machine units.

A buffer object binding created with glBindBuffer remains active until a different buffer object name is bound to the same target, or until the bound buffer object is deleted with glDeleteBuffers.

Once created, a named buffer object may be re-bound to any target as often as needed. However, the GL implementation may make choices about how to optimize the storage of a buffer object based on its initial binding target.

Errors

GL_INVALID_ENUM is generated if target is not one of the allowable values.

Associated Gets

glGet with argument GL_ARRAY_BUFFER_BINDING

glGet with argument GL_ELEMENT_ARRAY_BUFFER_BINDING

Examples

Load a vertex buffer into OpenGL for later rendering.
// data_size_in_bytes is the size in bytes of your vertex data.
// data_vertices is your actual vertex data, probably a huge array of floats

GLuint vertex_buffer; // Save this for later rendering
glGenBuffers(1, &vertex_buffer);
glBindBuffer(GL_ARRAY_BUFFER, vertex_buffer);
glBufferData(GL_ARRAY_BUFFER, data_size_in_bytes, 0, GL_STATIC_DRAW);
glBufferSubData(GL_ARRAY_BUFFER, 0, data_size_in_bytes, data_vertices);

GLint size = 0;
glGetBufferParameteriv(GL_ARRAY_BUFFER, GL_BUFFER_SIZE, &size);
if(data_size_in_bytes != size)
{
    glDeleteBuffers(1, &vertex_buffer);
    // Log the error
    return;
}

// Success
Load an index buffer into OpenGL for later rendering.
// data_size_in_bytes is the size in bytes of your vertex data.
// data_indices is an array of integer offsets into your vertex data.

GLuint index_buffer; // Save this for later rendering
glGenBuffers(1, &index_buffer);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, index_buffer);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, data_size_in_bytes, 0, GL_STATIC_DRAW);
glBufferSubData(GL_ELEMENT_ARRAY_BUFFER, 0, data_size_in_bytes, data_indices);

GLint size = 0;
glGetBufferParameteriv(GL_ELEMENT_ARRAY_BUFFER, GL_BUFFER_SIZE, &size);
if(data_size_in_bytes != size)
{
    glDeleteBuffers(1, &index_buffer);
    // Log the error
    return;
}

// Success
Render an indexed buffer object using texture UV and normal vertex attributes.
glBindBuffer(GL_ARRAY_BUFFER, vertex_buffer); // vertex_buffer is retrieved from glGenBuffers
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, index_buffer); // index_buffer is retrieved from glGenBuffers

glEnableVertexAttribArray(texcoord_attrib_index); // Attribute indexes were received from calls to glGetAttribLocation, or passed into glBindAttribLocation.
glEnableVertexAttribArray(normal_attrib_index);
glEnableVertexAttribArray(position_attrib_index);

// vertex_stride is the size of bytes of each vertex in the buffer object
// vertex_position_offset and kin are the offset in bytes of the position data
// in each vertex. For example if your vertex structure is
// [ position, texcoord, normal ] then position vertex_position_offset will
// have offset 0, vertex_texcoord_offset is 12 (position is 3 * sizeof(float)
// bytes large, and texcoord comes just after) and vertex_normal_offset is
// 20 = 5 * sizeof(float).
GLintptr vertex_texcoord_offset = 3 * sizeof(float);
GLintptr vertex_normal_offset = 5 * sizeof(float);
GLintptr vertex_position_offset = 0 * sizeof(float);

glVertexAttribPointer(texcoord_attrib_index, 2, GL_FLOAT, false, vertex_stride, (GLvoid*)vertex_texcoord_offset);
glVertexAttribPointer(normal_attrib_index, 3, GL_FLOAT, false, vertex_stride, (GLvoid*)vertex_normal_offset);
glVertexAttribPointer(position_attrib_index, 3, GL_FLOAT, false, vertex_stride, (GLvoid*)vertex_position_offset);

// num_vertices is the number of verts in your vertex_data.
// index_data is an array of unsigned int offsets into vertex_data.
glDrawElements(GL_TRIANGLES, num_vertices, GL_UNSIGNED_INT, NULL);

glDisableVertexAttribArray(position_attrib_index);
glDisableVertexAttribArray(texcoord_attrib_index);
glDisableVertexAttribArray(normal_attrib_index);

See Also

glDeleteBuffers, glGenBuffers, glGet, glIsBuffer

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