glDrawElementsInstanced

glDrawElementsInstanced: man3/glDrawElementsInstanced.xml

glDrawElementsInstanced behaves identically to glDrawElements except that primcount instances of the set 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. glDrawElementsInstanced has the same effect as:

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