<function>glIsRenderbuffer</function> returns <constant>GL_TRUE</constant> if <parameter>renderbuffer</parameter> is currently the name of a renderbuffer
object. If <parameter>renderbuffer</parameter> is zero, or if <parameter>renderbuffer</parameter> is not the name of a renderbuffer object, or if an error
occurs, <function>glIsRenderbuffer</function> returns <constant>GL_FALSE</constant>. If <parameter>renderbuffer</parameter> is a name returned by
<citerefentry><refentrytitle>glGenRenderbuffers</refentrytitle></citerefentry>, by that has not yet been bound through a call to
<citerefentry><refentrytitle>glBindRenderbuffer</refentrytitle></citerefentry> or <citerefentry><refentrytitle>glFramebufferRenderbuffer</refentrytitle></citerefentry>,
then the name is not a renderbuffer object and <function>glIsRenderbuffer</function> returns <constant>GL_FALSE</constant>.