From f53816a8fd9ec15ef03b5bf45472eda46e53c1ad Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Sat, 4 Nov 2023 21:05:35 +0000
Subject: Refactor to further simplify line/point operations

Adds another perf test
---
 game/geoData.cpp      | 18 +++++++++---------
 test/perf-geoData.cpp | 13 +++++++++++++
 2 files changed, 22 insertions(+), 9 deletions(-)

diff --git a/game/geoData.cpp b/game/geoData.cpp
index 5e49c94..c58658a 100644
--- a/game/geoData.cpp
+++ b/game/geoData.cpp
@@ -111,12 +111,16 @@ GeoData::PointFace::face(const GeoData * mesh) const
 }
 
 namespace {
-	[[nodiscard]] constexpr inline bool
-	pointLeftOfLine(const glm::vec2 p, const glm::vec2 e1, const glm::vec2 e2)
+	template<template<typename> typename Op>
+	[[nodiscard]] constexpr inline auto
+	pointLineOp(const glm::vec2 p, const glm::vec2 e1, const glm::vec2 e2)
 	{
-		return (e2.x - e1.x) * (p.y - e1.y) > (e2.y - e1.y) * (p.x - e1.x);
+		return Op {}((e2.x - e1.x) * (p.y - e1.y), (e2.y - e1.y) * (p.x - e1.x));
 	}
 
+	constexpr auto pointLeftOfLine = pointLineOp<std::greater>;
+	constexpr auto pointLeftOfOrOnLine = pointLineOp<std::greater_equal>;
+
 	static_assert(pointLeftOfLine({1, 2}, {1, 1}, {2, 2}));
 	static_assert(pointLeftOfLine({2, 1}, {2, 2}, {1, 1}));
 	static_assert(pointLeftOfLine({2, 2}, {1, 2}, {2, 1}));
@@ -217,12 +221,8 @@ GeoData::walkUntil(const PointFace & from, const glm::vec2 to, const std::functi
 bool
 GeoData::triangleContainsPoint(const glm::vec2 p, const Triangle<2> & t)
 {
-	const auto mul = [](const glm::vec2 a, const glm::vec2 b, const glm::vec2 c) {
-		return (a.x - b.x) * (c.y - b.y) - (a.y - b.y) * (c.x - b.x);
-	};
-	const auto det = mul(t[1], t[0], t[2]);
-
-	return det * mul(t[1], t[0], p) >= 0 && det * mul(t[2], t[1], p) >= 0 && det * mul(t[0], t[2], p) >= 0;
+	return pointLeftOfOrOnLine(p, t[0], t[1]) && pointLeftOfOrOnLine(p, t[1], t[2])
+			&& pointLeftOfOrOnLine(p, t[2], t[0]);
 }
 
 bool
diff --git a/test/perf-geoData.cpp b/test/perf-geoData.cpp
index e1546c1..2d79a90 100644
--- a/test/perf-geoData.cpp
+++ b/test/perf-geoData.cpp
@@ -11,8 +11,21 @@ namespace {
 			benchmark::DoNotOptimize(tm.findPoint({315555, 495556}));
 		}
 	}
+
+	void
+	terrain_walk(benchmark::State & state)
+	{
+		const glm::vec2 point {310001, 490000};
+		const GeoData::PointFace start {point, tm.findPoint(point)};
+		for (auto _ : state) {
+			tm.walk(start, {319999, 500000}, [](auto f) {
+				benchmark::DoNotOptimize(f);
+			});
+		}
+	}
 }
 
 BENCHMARK(terrain_findPoint);
+BENCHMARK(terrain_walk);
 
 BENCHMARK_MAIN();
-- 
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