From 2dd5c675afdfa2d8226a118c02eff7f3fe258821 Mon Sep 17 00:00:00 2001
From: Bruno BELANYI <brunobelanyi@gmail.com>
Date: Tue, 17 Mar 2020 13:41:52 +0100
Subject: [PATCH] library: core: add Camera implementation

---
 src/core/camera.rs | 69 ++++++++++++++++++++++++++++++++++++++++++++++
 src/core/mod.rs    |  3 ++
 2 files changed, 72 insertions(+)
 create mode 100644 src/core/camera.rs

diff --git a/src/core/camera.rs b/src/core/camera.rs
new file mode 100644
index 0000000..ce431e2
--- /dev/null
+++ b/src/core/camera.rs
@@ -0,0 +1,69 @@
+use super::super::{Point, Vector};
+use super::film::Film;
+
+/// Represent an abstract camera to observe the scene.
+#[derive(Debug, PartialEq)]
+pub struct Camera {
+    /// Where the camera is set in the scene (i.e: its focal point).
+    origin: Point,
+    /// The film to represent each pixel in the scene.
+    film: Film,
+}
+
+impl Camera {
+    pub fn new(
+        origin: Point,
+        forward: Vector,
+        up: Vector,
+        fov: f32,
+        dist_to_image: f32,
+        x: u32,
+        y: u32,
+    ) -> Camera {
+        let right = forward.cross(&up);
+        let center = origin + forward.normalize() * dist_to_image;
+        let screen_size = 2. * f32::tan(fov / 2.) * dist_to_image;
+        let film = Film::new(x, y, screen_size, center, up, right);
+        Camera { origin, film }
+    }
+
+    pub fn film(&self) -> &Film {
+        &self.film
+    }
+
+    pub fn origin(&self) -> &Point {
+        &self.origin
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn new_works() {
+        let cam = Camera::new(
+            Point::new(-1., 0., 0.),
+            Vector::new(1., 0., 0.),
+            Vector::new(0., 1., 0.),
+            2. * f32::atan(1.), /* 90° in radian */
+            1.,
+            1080,
+            1080,
+        );
+        assert_eq!(
+            cam,
+            Camera {
+                origin: Point::new(-1., 0., 0.),
+                film: Film::new(
+                    1080,
+                    1080,
+                    2.,
+                    Point::origin(),
+                    Vector::new(0., 1., 0.),
+                    Vector::new(0., 0., 1.),
+                )
+            }
+        )
+    }
+}
diff --git a/src/core/mod.rs b/src/core/mod.rs
index ac862d9..849639a 100644
--- a/src/core/mod.rs
+++ b/src/core/mod.rs
@@ -1,3 +1,6 @@
+pub mod camera;
+pub use camera::*;
+
 pub mod color;
 pub use color::*;