Provide a tangent at each traced point

src/bin/flat/main.rs

@@ -166,13 +166,13 @@ fn draw_ray_2(gc: &mut Vec<Draw>, space: &Space, camera: Location, dir: Vec3) {
 	gc.new_path();
 	gc.move_to(pos.x, pos.y);
 	for pt in &path.points[1..] {
-		gc.line_to(pt.x, pt.y);
+		gc.line_to(pt.pos.x, pt.pos.y);
 	}
 	let end_pos = *path
 		.points
 		.last()
 		.expect("the starting point is always in the path");
-	let dir_pos = end_pos + 1000.0 * path.end_dir;
+	let dir_pos = end_pos.forward(1000. / DT).pos;
 	gc.line_to(dir_pos.x, dir_pos.y);
 	gc.stroke();
 }

src/bin/wireframe/scene.rs

@@ -1,5 +1,5 @@
 use glam::*;
-use itertools::{chain, iproduct};
+use itertools::{chain, iproduct, Itertools};
 
 use refraction::ifaces::{DebugTraceable, Traceable};
 use refraction::tube::metric::Tube;
@@ -107,9 +107,9 @@ fn draw_ray_2(gc: &mut Vec<Line>, space: &Space, camera: Location, dir: Vec3) {
 	let end_pos = *pts
 		.last()
 		.expect("the starting point is always in the path");
-	let dir_pos = end_pos + 10000.0 * path.end_dir;
+	let dir_pos = end_pos.forward(10000.0);
 	pts.push(dir_pos);
-	gc.push(Line::Strip(pts));
+	gc.push(Line::Strip(pts.into_iter().map(|r| r.pos).collect()));
 }
 
 fn draw_fan_2(space: &Space, camera: Location, spread: f32) -> Vec<Line> {

src/ifaces.rs

@@ -1,5 +1,4 @@
 use crate::types::{Hit, Location, Ray};
-use glam::Vec3;
 
 pub trait Traceable {
 	/// Traces a ray from a given starting point. `ray` is relative to the camera.
@@ -19,8 +18,7 @@ pub trait OptimizedTraceable: Traceable {
 }
 
 pub struct RayPath {
-	pub points: Vec<Vec3>,
-	pub end_dir: Vec3,
+	pub points: Vec<Ray>,
 }
 
 pub trait DebugTraceable: Traceable {

src/tube/mod.rs

@@ -146,16 +146,25 @@ impl Space {
 			.collect()
 	}
 
-	pub fn line(&self, a: Vec3, b: Vec3, step: f32) -> Vec<Vec3> {
+	pub fn line(&self, a: Vec3, b: Vec3, step: f32) -> Vec<Ray> {
 		match self.which_subspace(a) {
-			Outer => vec![b],
+			Outer => vec![Ray {
+				pos: b,
+				dir: (b - a).normalize(),
+			}],
 			Inner => {
 				let cs = InnerCS(self.tube);
 				let n = ((b - a).length() / step) as usize + 1;
 				let a = cs.global_to_flat(a);
 				let b = cs.global_to_flat(b);
+				let dir = (b - a).normalize();
 				(1..=n)
-					.map(|k| cs.flat_to_global(a.lerp(b, k as f32 / n as f32)))
+					.map(|k| {
+						cs.flat_to_global(Ray {
+							pos: a.lerp(b, k as f32 / n as f32),
+							dir,
+						})
+					})
 					.collect()
 			}
 			Boundary => panic!("Can't draw a line here!"),
@@ -210,9 +219,9 @@ impl DebugTraceable for Space {
 		let mut hits = vec![];
 		let mut ray = self.camera_ray_to_abs(camera, ray);
 
-		let trace_to_flat = |points: &mut Vec<Vec3>, ray| {
+		let trace_to_flat = |points: &mut Vec<Ray>, ray| {
 			for ray in self.trace_iter(ray).skip(1) {
-				points.push(ray.pos);
+				points.push(ray);
 				if let Some(hitter) = self.obj_hitter(ray.pos) {
 					return (ray, hitter(self, ray));
 				}
@@ -220,18 +229,12 @@ impl DebugTraceable for Space {
 			unreachable!("Space::trace_iter terminated!")
 		};
 
-		points.push(ray.pos);
+		points.push(ray);
 		for _ in 0..100 {
 			let (ray_into_flat, ret) = trace_to_flat(&mut points, ray);
 			hits.extend(ret.objects); // TODO fix distance
 			let Some(ray_outta_flat) = ret.end else {
-				return (
-					hits,
-					RayPath {
-						points,
-						end_dir: ray_into_flat.dir.normalize(),
-					},
-				);
+				return (hits, RayPath { points });
 			};
 			points.extend(self.line(ray_into_flat.pos, ray_outta_flat.pos, 10.0));
 			ray = ray_outta_flat;