zbuffer writing without rendering

hello,
i’d like to write a geometry in the zbuffer without rendering it on the screen, but can’t find how to do that.

any idea ?

regards
Adrien

Not an advanced question, you know.
glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);

sorry for that, and thanks for the answer

Don’t forget to finish with
glColormask( GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE );