1 files changed, 68 insertions, 0 deletions
diff --git a/physics/src/renderer/mod.rs b/physics/src/renderer/mod.rs
new file mode 100644
index 0000000..63894b3
--- /dev/null
+++ b/physics/src/renderer/mod.rs
@@ -0,0 +1,68 @@
+use nalgebra::{Point2, SMatrix};
+
+use crate::{
+    algebra::subspace::Plane,
+    algebra::{Point, Scalar, Vector, N},
+};
+
+pub struct Camera {
+    plane: Plane,
+    up: Vector,
+    origin: Point,
+    world_to_screen_space: SMatrix<Scalar, 2, N>,
+    screen_space_to_world: SMatrix<Scalar, N, 2>,
+}
+
+impl Camera {
+    pub fn new(origin: Point, up: Vector, right: Vector) -> Self {
+        assert!(
+            up.dot(&right) == 0.0,
+            "Up and right vectors must be orthogonal"
+        );
+        let plane = Plane::new(origin, [up, right]);
+
+        let screen_space_to_world = SMatrix::<Scalar, N, 2>::from_columns(&[right, up]);
+        let world_to_screen_space = screen_space_to_world.pseudo_inverse(0.001).unwrap();
+
+        Self {
+            plane,
+            up,
+            origin,
+            world_to_screen_space,
+            screen_space_to_world,
+        }
+    }
+
+    pub fn world_to_screen_space(&self, point: Point) -> Point2<Scalar> {
+        let projected = self.plane.project_point(point);
+        let in_screen_space = self.world_to_screen_space * (projected - self.origin);
+        in_screen_space.into()
+    }
+    pub fn screen_space_to_world(&self, point: Point2<Scalar>) -> Point {
+        (self.screen_space_to_world * point) + self.origin.coords
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::algebra::{Point, Vector};
+
+    use super::Camera;
+
+    #[test]
+    fn test_projection() {
+        let camera = Camera::new(
+            Point::new(1.0, 0.0),
+            Vector::new(1.0, 2.0),
+            Vector::new(2.0, -1.0),
+        );
+
+        let point = Point::new(3.0, 1.0);
+
+        let diff = camera.world_to_screen_space * point - Point::new(1.0, 1.0);
+        assert!(
+            diff.norm() < 0.001,
+            "Camera translated point into screen_space incorrectly"
+        );
+    }
+}