glDrawArraysInstanced

glDrawArraysInstanced: man4/glDrawArraysInstanced.xml

glDrawArraysInstanced behaves identically to glDrawArrays except that primcount instances of the range of elements are executed and the value of the internal counter instanceID advances for each iteration. instanceID is an internal 32-bit integer counter that may be read by a vertex shader as gl_InstanceID. glDrawArraysInstanced has the same effect as:

if ( mode or count is invalid )
    generate appropriate error
else {
    for (int i = 0; i < primcount ; i++) {
        instanceID = i;
        glDrawArrays(mode, first, count);
    }
    instanceID = 0;
}