Function glDrawArrays

glDrawArrays specifies multiple geometric primitives with very few subroutine calls. Instead of calling a GL procedure to pass each individual vertex, normal, texture coordinate, edge flag, or color, you can prespecify separate arrays of vertices, normals, and colors 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.

Vertex attributes that are modified by glDrawArrays have an unspecified value after glDrawArrays returns. Attributes that aren't modified remain well defined.

Summary

render primitives from array data

Example

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);
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Tutorial

Songho - OpenGL Vertex Array

Tutorial

open.gl - Depth and Stencil Buffers

Tutorial

open.gl - Geometry Shaders

Tutorial

open.gl - The Graphics Pipeline

Tutorial

open.gl - Transform Feedback

Tutorial

opengl-tutorial.org - Tutorial 2 : The first triangle

Tutorial

opengl-tutorial.org - Tutorial 4 : A Colored Cube

See

glDrawArrays