diff --git a/src/bin/flat/ifaces.rs b/src/bin/flat/ifaces.rs
new file mode 100644
index 0000000..d28be75
--- /dev/null
+++ b/src/bin/flat/ifaces.rs
@@ -0,0 +1,29 @@
+use crate::types::{Hit, Location, Ray};
+use glam::Vec2;
+
+pub trait Traceable {
+	/// Traces a ray from a given starting point. `ray` is relative to the camera.
+	///
+	/// Returns all objects the ray touched. `Hit::distance` is along the ray; it may be a rough estimate except, when two objects overlap the difference of corresponding `distance`s shall be correct.
+	fn trace(&self, camera: Location, ray: Ray) -> Vec<Hit>;
+}
+
+pub trait OptimizedTraceable: Traceable {
+	type State;
+
+	/// Prepares tracing from a given starting point. `ray` is relative to the camera.
+	fn init(&self, camera: Location, ray: Ray) -> Self::State;
+
+	/// Similar to [`Traceable::trace`] but allows stopping early.
+	fn trace(&self, state: Self::State) -> (Option<Self::State>, Vec<Hit>);
+}
+
+pub struct RayPath {
+	pub points: Vec<Vec2>,
+	pub end_dir: Vec2,
+}
+
+pub trait DebugTraceable: Traceable {
+	/// Identical to [`Traceable::trace`], except also returns the ray path.
+	fn trace_dbg(&self, camera: Location, ray: Ray) -> (Vec<Hit>, RayPath);
+}
diff --git a/src/bin/flat/main.rs b/src/bin/flat/main.rs
index 235fa50..26cac12 100644
--- a/src/bin/flat/main.rs
+++ b/src/bin/flat/main.rs
@@ -14,6 +14,7 @@ use types::{Location, Object, Ray};
 
 mod float_fun;
 mod fns;
+mod ifaces;
 mod riemann;
 mod tube;
 mod types;