From 97286085ab6975dac32e91fcafa16f498ae6e698 Mon Sep 17 00:00:00 2001
From: numzero <numzer0@yandex.ru>
Date: Sat, 14 Sep 2024 15:55:01 +0300
Subject: [PATCH] Allow getting all ray-mesh intersections (useful for
 translucent objects)

---
 src/mesh_tracer.rs | 29 ++++++++++++++++-------------
 1 file changed, 16 insertions(+), 13 deletions(-)

diff --git a/src/mesh_tracer.rs b/src/mesh_tracer.rs
index bb9bbc4..e6fb308 100644
--- a/src/mesh_tracer.rs
+++ b/src/mesh_tracer.rs
@@ -8,13 +8,15 @@ pub struct TraceResult {
 	pub normal: Vec3,
 }
 
-pub fn trace_to_mesh(mesh: &Mesh, base: Vec3, ray: Vec3) -> Option<TraceResult> {
-	let mut ret: Option<TraceResult> = None;
-	let mut dist = f32::INFINITY;
-	for f in mesh {
+pub fn trace_to_mesh_all(
+	mesh: &Mesh,
+	base: Vec3,
+	ray: Vec3,
+) -> impl Iterator<Item = TraceResult> + '_ {
+	mesh.iter().filter_map(move |f| {
 		let fs = (0..3).map(|k| edge_dist(f.vertices[k], f.vertices[(k + 1) % 3], base, ray));
 		if fs.into_iter().any(|f| f < 0.0) {
-			continue;
+			return None;
 		}
 		let m = mat3(
 			f.vertices[1] - f.vertices[0],
@@ -23,16 +25,17 @@ pub fn trace_to_mesh(mesh: &Mesh, base: Vec3, ray: Vec3) -> Option<TraceResult>
 		);
 		let m = m.inverse();
 		let rel = m * (base - f.vertices[0]);
-		if rel.z > dist {
-			continue;
-		}
-		dist = rel.z;
-		ret = Some(TraceResult {
+		Some(TraceResult {
 			distance: rel.z,
 			normal: f.normal,
-		});
-	}
-	ret
+		})
+	})
+}
+
+pub fn trace_to_mesh(mesh: &Mesh, base: Vec3, ray: Vec3) -> Option<TraceResult> {
+	trace_to_mesh_all(mesh, base, ray)
+		.filter(|tr| tr.distance >= 0.0)
+		.min_by(|a, b| a.distance.total_cmp(&b.distance))
 }
 
 fn edge_dist(a: Vec3, b: Vec3, base: Vec3, dir: Vec3) -> f32 {