Joel Garman's Tunnel filmed in the Durie Hill tunnel and tower is one of 16 finalists in New Zealand's Tropfest.
Mr Garman has a year left of his Bachelor of Digital Media degree, and Tunnel is his "first big try at directing".
Tunnel stars his grandfather Tom Rowley, and friend Jarred Kirkwood is the soldier who dies and has to cross over to the other side.
Mr Rowley was a natural, says his grandson. "He was great, he had learned all his lines."
The short film is about conflict, and the rules are that the message must be delivered in a maximum of seven minutes.
"It's about redemption, forgiveness, honour," says Mr Garman. "Every soldier has his tunnel".
Mr Garman's film is an anti-war message, but the "old soldier" is pro-war.
The former Wanganui High School student is home for the summer from the Southern Institute of Technology in Invercargill.
The tunnel was the hardest place to film in, Mr Garman said, because as soon as people entered, they could be heard at the other end, where filming was taking place.
Academy Award nominee Taika Waititi and actor Sam Neill have been named as official ambassadors of Tropfest NZ, and are keen to celebrate the festival's arrival to New Zealand.
Waititi said short films were an incredible learning ground for aspiring film-makers to play and make mistakes ... "things that are key to becoming a filmic story-teller".
Waititi and Neill join other ambassadors, actor Martin Henderson, director/producer/actor Katie Wolfe, actor Robyn Malcolm and director/screenwriter Vincent Ward.
Mr Garman says the big prize is the"plug-ins" to the Hollywood film industry for the lucky winner.
A prize is offered to the best director, and the winner receives flights to Los Angeles, five days accommodation and $500 cash courtesy of the Motion Picture Association (MPA) and the New Zealand Federation Against Copyright Theft (NZFACT).
Tunnel will be on the big screen at the inaugural Tropfest NZoutdoor gala event at the TSB Bowl of Brooklands with the other finalists on January 27.
The winning film will be announced on the night. It's a free event and those interested are invited along, and to "bring a picnic and join in the buzz".
Tropfest NZ says the event has been designed to encourage filmmakers from the grassroots up. The venue opens at 5pm, films start 6.30pm.
Tropfest is the world's largest short film festival and has become known as the world's first truly global film festival.
Tropfest began in 1993 as a screening for 200 people in a cafe in Sydney but has since become the largest platform for short films in the world.
In the past two decades, Tropfest has become recognised as one of the world's most exciting launch-pads for emerging film-makers and has secured the support of some of the big names in the international film community including Hugh Jackman, Nicole Kidman, Russell Crowe, Geoffrey Rush, Liev Schreiber and Tobey Maguire.