From b22c36a9831c325e2ca08d5052a712d9bf9c1da1 Mon Sep 17 00:00:00 2001
From: numzero <numzer0@yandex.ru>
Date: Mon, 10 Jun 2024 00:10:22 +0300
Subject: [PATCH] Cleanup math

---
 src/bin/flat.rs | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/src/bin/flat.rs b/src/bin/flat.rs
index bd06bf6..f4e2f85 100644
--- a/src/bin/flat.rs
+++ b/src/bin/flat.rs
@@ -536,14 +536,13 @@ struct Rect {
 
 impl Rect {
 	fn γ(&self) -> f32 { self.external_halflength / self.internal_halflength }
-	fn ri(&self) -> f32 { self.internal_halflength }
-	fn a(&self) -> f32 { (1.0 - self.γ()) / self.ri() }
+	fn a(&self) -> f32 { -(self.γ() - 1.0) / self.internal_halflength }
 	fn b(&self) -> f32 { 2.0 * self.γ() - 1.0 }
 
-	fn root(&self, x: f32) -> f32 { ((2.0 * self.γ() - 1.0).powi(2) + 4.0 * (1.0 - self.γ()) * x / self.ri()).sqrt() }
+	fn root(&self, x: f32) -> f32 { (self.b().powi(2) + 4.0 * self.a() * x).sqrt() }
 	fn d(&self, u: f32) -> f32 { 2.0 * self.a() * u + self.b() }
 	pub fn x(&self, u: f32) -> f32 { (self.a() * u.abs() + self.b()) * u }
-	pub fn u(&self, x: f32) -> f32 { 0.5 * self.ri() * (1.0 - 2.0 * self.γ() + self.root(x.abs())) / (1.0 - self.γ()) * x.signum() }
+	pub fn u(&self, x: f32) -> f32 { 0.5 * x.signum() * (-self.b() + self.root(x.abs())) / self.a() }
 	pub fn dx(&self, u: f32, du: f32) -> f32 { du * self.d(u.abs()) }
 	pub fn du(&self, x: f32, dx: f32) -> f32 { dx / self.root(x.abs()) }
 }
@@ -608,7 +607,7 @@ impl Metric for Rect {
 		let sy = if y <= self.external_halflength { 1.0 / self.root(y) } else { 1.0 };
 		let s = sy.lerp(1.0, sx);
 		let dsx_dx = if x > self.inner_radius && x < self.outer_radius { pos.x.signum() / (self.outer_radius - self.inner_radius) } else { 0.0 };
-		let dsy_dy = if y <= self.external_halflength { -2.0 * (1.0 - self.γ()) / self.internal_halflength * sy.powi(3) * pos.y.signum() } else { 0.0 };
+		let dsy_dy = if y <= self.external_halflength { -2.0 * pos.y.signum() * self.a() * sy.powi(3) } else { 0.0 };
 		let ds2_dx = 2.0 * s * (1.0 - sy) * dsx_dx;
 		let ds2_dy = 2.0 * s * (1.0 - sx) * dsy_dy;
 		[