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# docs.GL

OpenGL 4
OpenGL 3
OpenGL 2
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OpenGL ES 2

# glEnableVertexAttribArray

## Name

glEnableVertexAttribArray — Enable or disable a generic vertex attribute array

## C Specification

`void glEnableVertexAttribArray(` | GLuint | index`)`;

`void glDisableVertexAttribArray(` | GLuint | index`)`;

## Parameters

`index`

  Specifies the index of the generic vertex attribute to be enabled or disabled.

## Description

`glEnableVertexAttribArray` enables the generic vertex attribute array specified by `index`. `glDisableVertexAttribArray` disables the generic vertex attribute array specified by `index`. By default, all client-side capabilities are disabled, including all generic vertex attribute arrays. If enabled, the values in the generic vertex attribute array will be accessed and used for rendering when calls are made to vertex array commands such as glDrawArrays, glDrawElements, glDrawRangeElements, glMultiDrawElements, or glMultiDrawArrays.

## Errors

`GL_INVALID_VALUE` is generated if `index` is greater than or equal to `GL_MAX_VERTEX_ATTRIBS`.

`GL_INVALID_OPERATION` is generated if there is no current vertex array object.

## Associated Gets

glGet with argument `GL_MAX_VERTEX_ATTRIBS`

glGetVertexAttrib with arguments `index` and `GL_VERTEX_ATTRIB_ARRAY_ENABLED` ``

glGetVertexAttribPointerv with arguments `index` and `GL_VERTEX_ATTRIB_ARRAY_POINTER`

## Examples

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);

## Tutorials

Learning Modern 3D Graphics Programming - Chapter 5. Objects in Depth [Vertex Array Objects, Indexed Drawing]
open.gl - Geometry Shaders
open.gl - Textures Objects and Parameters
open.gl - The Graphics Pipeline
open.gl - Transform Feedback
opengl-tutorial.org - Particles / Instancing
opengl-tutorial.org - Tutorial 13 : Normal Mapping
opengl-tutorial.org - Tutorial 2 : The first triangle
opengl-tutorial.org - Tutorial 4 : A Colored Cube
opengl-tutorial.org - Tutorial 8 : Basic shading

## See Also

glBindAttribLocation, glDrawArrays, glDrawElements, glDrawRangeElements, glMultiDrawElements, glVertexAttrib, glVertexAttribPointer

## Copyright

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. https://opencontent.org/openpub/.

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