Altered is a 2006 science fiction horror film directed by Eduardo Sánchez and written by Jamie Nash.
 It was Sánchez's first solo effort as director following his co-directing of "The Blair Witch Project" in 1999.
Blair Witch is a horror film franchise distributed by Artisan Entertainment (now Lionsgate) and produced by Haxan Films that consists of three feature films and various merchandise products.
 The development of the franchise's first installment, "The Blair Witch Project", started in 1993.
 The filmmakers Eduardo Sánchez and Daniel Myrick wrote a 35-page outline of a story with the dialogue to be improvised.
 Filming began in 1997 and lasted eight days.
 The film follows the disappearance of three student filmmakers in the woods near Burkittsville, Maryland while shooting a documentary on the local legend known as the "Blair Witch".
Blair Witch is a 2016 American found footage supernatural horror film directed by Adam Wingard and written by Simon Barrett.
 It is the third official film in the "Blair Witch" series and a direct sequel to the 1999 film "The Blair Witch Project", ignoring the events of its 2000 follow-up film "", given the events of that film being a film within a film.
 "Blair Witch" stars James Allen McCune, Callie Hernandez, Brandon Scott, Corbin Reid, Wes Robinson, and Valorie Curry.
 The film, shot in a found footage style, follows a group of college students and their local guides who venture into the Black Hills Forest in Maryland to uncover the mysteries surrounding the disappearance years ago of Heather Donahue, the sister of one of the characters.
 Initially, the film's connection to the "Blair Witch" franchise was kept secret, with the film having been shot under the fake title, "The Woods".
Book of Shadows: Blair Witch 2 (also known as Blair Witch 2: Book of Shadows) is a 2000 American psychological horror film, directed and co-written by Joe Berlinger and starring Jeffrey Donovan, Stephen Barker Turner, Kim Director, Erica Leerhsen and Tristine Skyler.
 The film was immediately greenlit upon pitch due to the surprising success of its predecessor, the wildly successful 1999 film "The Blair Witch Project".
 Stylistically different from the first film, the story revolves around a group of people fascinated by the mythology surrounding "The Blair Witch Project" movie and go into the Black Hills where the film was shot and documents their subsequent psychological unraveling.
Ben Rock is an American film and theatre director, based in Los Angeles.
 Rock's career was launched when he served as production designer on the independent sensation "The Blair Witch Project" made by fellow University of Central Florida graduates Daniel Myrick, Eduardo Sanchez, Greggory R. Hale, Robin Cowie and Michael Monello.
 Rock created the infamous "stick man" symbol that became synonymous with the hit film.
Christophe Gans (born 11 March 1960) is a French film director, producer and screenwriter, who specializes in horror and fantasy movies.
Eduardo Miguel Sánchez-Quiros (born December 20, 1968) is a Cuban-born American director, most famous for co-directing and writing the 1999 psychological horror "The Blair Witch Project" with Daniel Myrick.
The Objective is a 2008 science fiction horror film directed by Daniel Myrick who also directed "The Blair Witch Project" and "Believers", starring Jonas Ball, Matthew R. Anderson, and Michael C. Williams.
 It premiered in Morocco in April 2008 and in the United States in February 2009.
Daniel Myrick (born September 3, 1963) is an American film director most famous for horror films, especially for co-directing and writing the 1999 psychological horror "The Blair Witch Project" with Eduardo Sánchez, for which they won the Independent Spirit John Cassavetes Award.
The Blair Witch Project is a 1999 American psychological horror film written, directed, and edited by Daniel Myrick and Eduardo Sánchez.
 It tells the fictional story of three student filmmakers (Heather Donahue, Michael C. Williams, and Joshua Leonard) who hike in the Black Hills near Burkittsville, Maryland, in 1994 to film a documentary about a local legend known as the Blair Witch.
 The three disappear, but their video and sound equipment (along with most of the footage they shot) is discovered a year later; the "recovered footage" is the film the viewer is watching.

Question: Which film director co-directed the 1999 psychological horror "The Blair Witch Project" with Eduardo Sánchez, Christophe Gans or Daniel Myrick?
Answer: Daniel Myrick