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glDrawArrays

Name

glDrawArrays — render primitives from array data

C Specification

void glDrawArrays( GLenum mode,
  GLint first,
  GLsizei count);
 

Parameters

mode

Specifies what kind of primitives to render. Symbolic constants GL_POINTS, GL_LINE_STRIP, GL_LINE_LOOP, GL_LINES, GL_TRIANGLE_STRIP, GL_TRIANGLE_FAN and GL_TRIANGLES are accepted.

first

Specifies the starting index in the enabled arrays.

count

Specifies the number of indices to be rendered.

Description

glDrawArrays specifies multiple geometric primitives with very few subroutine calls. It is possible to prespecify separate arrays of attributes and use them to construct a sequence of primitives with a single call to glDrawArrays.

When glDrawArrays is called, it uses count sequential elements from each enabled array to construct a sequence of geometric primitives, beginning with element first. mode specifies what kind of primitives are constructed and how the array elements construct those primitives.

To enable and disable a generic vertex attribute array, call glEnableVertexAttribArray and glDisableVertexAttribArray.

If an array corresponding to a generic attribute required by a vertex shader is not enabled, then the corresponding element is taken from the current generic attribute state.

Errors

GL_INVALID_ENUM is generated if mode is not an accepted value.

GL_INVALID_VALUE is generated if count is negative.

GL_INVALID_OPERATION is generated if a non-zero buffer object name is bound to an enabled array and the buffer object's data store is currently mapped.

GL_INVALID_FRAMEBUFFER_OPERATION is generated if the currently bound framebuffer is not framebuffer complete (i.e. the return value from glCheckFramebufferStatus is not GL_FRAMEBUFFER_COMPLETE).

GL_INVALID_OPERATION is generated if recording the vertices of a primitive to the buffer objects being used for transform feedback purposes would result in either exceeding the limits of any buffer object’s size, or in exceeding the end position offset + size - 1, as set by glBindBufferRange.

Examples

Render a vertex array (not loaded into OpenGL) using texture UV, color, and normal vertex attributes.
glEnableVertexAttribArray(texcoord_attrib_index); // Attribute indexes were received from calls to glGetAttribLocation, or passed into glBindAttribLocation.
glEnableVertexAttribArray(normal_attrib_index);
glEnableVertexAttribArray(color_attrib_index);
glEnableVertexAttribArray(position_attrib_index);

glVertexAttribPointer(texcoord_attrib_index, 2, GL_FLOAT, false, 0, texcoords_data); // texcoords_data is a float*, 2 per vertex, representing UV coordinates.
glVertexAttribPointer(normal_attrib_index, 3, GL_FLOAT, false, 0, normals_data); // normals_data is a float*, 3 per vertex, representing normal vectors.
glVertexAttribPointer(color_attrib_index, 3, GL_UNSIGNED_BYTE, true, sizeof(unsigned char)*3, colors_data); // colors_data is a unsigned char*, 3 per vertex, representing the color of each vertex.
glVertexAttribPointer(position_attrib_index, 3, GL_FLOAT, false, 0, vertex_data); // vertex_data is a float*, 3 per vertex, representing the position of each vertex

glDrawArrays(GL_TRIANGLES, 0, vertex_count); // vertex_count is an integer containing the number of indices to be rendered

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

API Version Support

OpenGL ES API Version
Function Name 2.0 3.0 3.1
glDrawArrays
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