From 80433d5ed6e379476fbf1a084e5b0688fbd0ef32 Mon Sep 17 00:00:00 2001
From: numzero <numzer0@yandex.ru>
Date: Sat, 17 Oct 2026 23:04:31 +0300
Subject: [PATCH] refactor mesh construction

---
 src/crown_gear.rs | 123 +++++++++++-----------------------------------
 1 file changed, 29 insertions(+), 94 deletions(-)

diff --git a/src/crown_gear.rs b/src/crown_gear.rs
index d3e1b6b..1cfe93a 100644
--- a/src/crown_gear.rs
+++ b/src/crown_gear.rs
@@ -1,6 +1,6 @@
 use std::f32::consts::PI;
 
-use glam::{Vec3, vec3};
+use glam::{Mat3A, Vec3, vec3};
 
 use crate::{
 	profile::Profile,
@@ -27,104 +27,39 @@ impl CrownGear {
 		mesh.faces.reserve_exact(8 * sides);
 		for k in 0..sides {
 			let t = k as f32 / sides as f32;
-			let phi = 2.0 * PI * t;
-			let (s, c) = phi.sin_cos();
+			let rot = Mat3A::from_rotation_z(2.0 * PI * t);
+
 			let tooth = t * teeth;
 			let y = self.profile.y_from_tooth(tooth);
-			let eps = 1e-3;
-			let dy_dt = teeth
-				* (self.profile.y_from_tooth(tooth + eps) - self.profile.y_from_tooth(tooth - eps))
-				/ (2.0 * eps);
 
-			let v_radial = vec3(c * self.pitch_radius, s * self.pitch_radius, y);
-			let v_tan = vec3(-2.0 * PI * s, 2.0 * PI * c, dy_dt / self.pitch_radius);
-			let n_top = v_radial.cross(v_tan).normalize();
+			let n_top = {
+				let eps = 1e-3;
+				let dy_dt = teeth
+					* (self.profile.y_from_tooth(tooth + eps)
+						- self.profile.y_from_tooth(tooth - eps))
+					/ (2.0 * eps);
+				vec3(-2.0 * PI * y, -dy_dt, 2.0 * PI * self.pitch_radius)
+			};
 
-			let n_top = vec3(
-				s * dy_dt - 2.0 * PI * c * y,
-				-c * dy_dt - 2.0 * PI * s * y,
-				2.0 * PI * self.pitch_radius,
-			);
-
-			// top
-			mesh.vertices.push(Vertex {
-				position: vec3(
-					c * self.outer_radius,
-					s * self.outer_radius,
-					outer_scale * y,
-				),
+			let vertex = |x, z, n| Vertex {
+				position: rot * vec3(x, 0.0, z),
 				color,
-				normal: n_top,
-			});
-			mesh.vertices.push(Vertex {
-				position: vec3(
-					c * self.inner_radius,
-					s * self.inner_radius,
-					inner_scale * y,
-				),
-				color,
-				normal: n_top,
-			});
-
-			// bottom
-			mesh.vertices.push(Vertex {
-				position: vec3(
-					c * self.inner_radius,
-					s * self.inner_radius,
-					-self.base_thickness,
-				),
-				color,
-				normal: vec3(0.0, 0.0, -1.0),
-			});
-			mesh.vertices.push(Vertex {
-				position: vec3(
-					c * self.outer_radius,
-					s * self.outer_radius,
-					-self.base_thickness,
-				),
-				color,
-				normal: vec3(0.0, 0.0, -1.0),
-			});
-
-			// inner
-			mesh.vertices.push(Vertex {
-				position: vec3(
-					c * self.inner_radius,
-					s * self.inner_radius,
-					inner_scale * y,
-				),
-				color,
-				normal: vec3(-c, -s, 0.0),
-			});
-			mesh.vertices.push(Vertex {
-				position: vec3(
-					c * self.inner_radius,
-					s * self.inner_radius,
-					-self.base_thickness,
-				),
-				color,
-				normal: vec3(-c, -s, 0.0),
-			});
-
-			// outer
-			mesh.vertices.push(Vertex {
-				position: vec3(
-					c * self.outer_radius,
-					s * self.outer_radius,
-					-self.base_thickness,
-				),
-				color,
-				normal: vec3(c, s, 0.0),
-			});
-			mesh.vertices.push(Vertex {
-				position: vec3(
-					c * self.outer_radius,
-					s * self.outer_radius,
-					outer_scale * y,
-				),
-				color,
-				normal: vec3(c, s, 0.0),
-			});
+				normal: n,
+			};
+			mesh.vertices.extend([
+				// top
+				vertex(self.outer_radius, outer_scale * y, n_top),
+				vertex(self.inner_radius, inner_scale * y, n_top),
+				// bottom
+				vertex(self.inner_radius, -self.base_thickness, -Vec3::Z),
+				vertex(self.outer_radius, -self.base_thickness, -Vec3::Z),
+				// inner
+				vertex(self.inner_radius, inner_scale * y, -Vec3::X),
+				vertex(self.inner_radius, -self.base_thickness, -Vec3::X),
+				// outer
+				vertex(self.outer_radius, -self.base_thickness, Vec3::X),
+				vertex(self.outer_radius, outer_scale * y, Vec3::X),
+			]);
 
 			let base1 = 8 * k;
 			let base2 = 8 * ((k + 1) % sides);