camera: add basic Camera object.

rtchallenge/src/camera.rs

@@ -0,0 +1,73 @@
+use crate::matrices::Matrix4x4;
+
+pub struct Camera {
+    hsize: usize,
+    vsize: usize,
+    field_of_view: f32,
+    transform: Matrix4x4,
+    pixel_size: f32,
+    half_width: f32,
+    half_height: f32,
+}
+
+impl Camera {
+    /// Create a camera with a canvas of pixel hsize (height) and vsize (width)
+    /// with the given field of view (in radians).
+    ///
+    /// # Examples
+    /// ```
+    /// use std::f32::consts::PI;
+    ///
+    /// use rtchallenge::{camera::Camera, matrices::Matrix4x4};
+    ///
+    /// let hsize = 160;
+    /// let vsize = 120;
+    /// let field_of_view = PI / 2.;
+    /// let c = Camera::new(hsize, vsize, field_of_view);
+    /// assert_eq!(c.hsize(), 160);
+    /// assert_eq!(c.vsize(), 120);
+    /// assert_eq!(c.transform(), Matrix4x4::identity());
+    ///
+    /// // Pixel size for a horizontal canvas.
+    /// let c = Camera::new(200, 150, PI / 2.);
+    /// assert_eq!(c.pixel_size(), 0.01);
+    ///
+    /// // Pixel size for a horizontal canvas.
+    /// let c = Camera::new(150, 200, PI / 2.);
+    /// assert_eq!(c.pixel_size(), 0.01);
+    /// ```
+    pub fn new(hsize: usize, vsize: usize, field_of_view: f32) -> Camera {
+        let half_view = (field_of_view / 2.).tan();
+        let aspect = hsize as f32 / vsize as f32;
+        let (half_width, half_height) = if aspect >= 1. {
+            (half_view, half_view / aspect)
+        } else {
+            (half_view * aspect, half_view)
+        };
+        let pixel_size = 2. * half_width / hsize as f32;
+        Camera {
+            hsize,
+            vsize,
+            field_of_view,
+            transform: Matrix4x4::identity(),
+            pixel_size,
+            half_height,
+            half_width,
+        }
+    }
+    pub fn hsize(&self) -> usize {
+        self.hsize
+    }
+    pub fn vsize(&self) -> usize {
+        self.vsize
+    }
+    pub fn field_of_view(&self) -> f32 {
+        self.field_of_view
+    }
+    pub fn transform(&self) -> Matrix4x4 {
+        self.transform
+    }
+    pub fn pixel_size(&self) -> f32 {
+        self.pixel_size
+    }
+}

rtchallenge/src/lib.rs

@@ -1,3 +1,4 @@
+pub mod camera;
 pub mod canvas;
 pub mod intersections;
 pub mod lights;