"Apostle," the trick horse owned and trained by David Davis and which played the role of Caleb in the film, is a Black Overo trained to lie on his side on command - something very few horses will do. During filming, Apostle would lie on his side for about 7 minutes at a time before getting up. Among his many other tricks, Apostle is also trained to limp on command, favoring his right front leg as though it's injured. The film's director had scripted and storyboarded a scene showing Caleb limping to the barn following the accident, but because of running behind schedule during production with a skeleton crew, was unable to get that shot.
To depict a car colliding with a horse, the sequence combines a composited virtual 3-D CGI horse with live action footage of the car and the real horse (to depict the horse hitting the ground after the collision). For the shots of the horse laying in front of the car after being hit, the production used a life-size dummy horse made with the very same black and white markings as the real horse.
To depict the horse landing on the snow as if knocked over by the car, David Davis, the owner-trainer of "Apostle," commanded the trick horse to lie down on his side. Filmed in slow-motion and combined with CGI bits of flying snow and a small "explosion" of snow particles where Apostle's head touched down, the shot of Apostle laying down gives the illusion of a very fast and hard landing. CGI "steam" was used both in this slow-motion shot to depict vaporized breath coming from the horse's nostrils, as well as in the shot with the dummy horse.
Digital animators Demetrius Owens and Joe Daniels used reference photos of the trick horse as well as live-action reference footage to create a convincing CGI virtual horse. Joe's CGI lighting effects and slo-mo snow particles completed the illusion.
The dummy horse was created at the workshop of Robert Kurtzman's Creature Corps, one of the top special effects studios in the country, using photographs of the film's trick horse Apostle to match his unique black-and-white markings.
The dummy horse is now in residence leaning against the wall inside the Hardinsburg, Indiana barn of David Davis, where it routinely fools unsuspecting passersby.