From 560bfce98146895cfd8429150792d49a18e24d98 Mon Sep 17 00:00:00 2001
From: Dan Goodliffe <dan@randomdan.homeip.net>
Date: Sun, 9 Apr 2023 13:15:46 +0100
Subject: Add lots of split required stuff to geometric plane

---
 lib/geometricPlane.cpp | 19 +++++++++++++++++++
 lib/geometricPlane.h   | 10 ++++++++++
 2 files changed, 29 insertions(+)

diff --git a/lib/geometricPlane.cpp b/lib/geometricPlane.cpp
index cb52997..71216c1 100644
--- a/lib/geometricPlane.cpp
+++ b/lib/geometricPlane.cpp
@@ -1,5 +1,7 @@
 #include "geometricPlane.h"
+#include "ray.hpp"
 #include <glm/geometric.hpp>
+#include <glm/gtx/intersect.hpp>
 
 GeometricPlane::PlaneRelation
 GeometricPlane::getRelation(glm::vec3 p) const
@@ -7,3 +9,20 @@ GeometricPlane::getRelation(glm::vec3 p) const
 	const auto d = glm::dot(normal, p - origin);
 	return d < 0.f ? PlaneRelation::Below : d > 0.f ? PlaneRelation::Above : PlaneRelation::On;
 }
+
+bool
+GeometricPlane::isIntersect(PlaneRelation a, PlaneRelation b)
+{
+	return ((a == PlaneRelation::Above && b == PlaneRelation::Below)
+			|| (a == PlaneRelation::Below && b == PlaneRelation::Above));
+}
+
+std::optional<GeometricPlane::DistAndPosition>
+GeometricPlane::getRayIntersectPosition(const Ray & ray) const
+{
+	float dist {};
+	if (!glm::intersectRayPlane(ray.start, ray.direction, origin, normal, dist)) {
+		return {};
+	}
+	return DistAndPosition {dist, ray.start + (ray.direction * dist)};
+}
diff --git a/lib/geometricPlane.h b/lib/geometricPlane.h
index 96816f2..dc8df50 100644
--- a/lib/geometricPlane.h
+++ b/lib/geometricPlane.h
@@ -1,12 +1,22 @@
 #pragma once
 
 #include <glm/vec3.hpp>
+#include <optional>
+
+class Ray;
 
 class GeometricPlane {
 public:
+	struct DistAndPosition {
+		float dist;
+		glm::vec3 position;
+	};
 	enum class PlaneRelation { Above, Below, On };
 
 	glm::vec3 origin, normal;
 
 	PlaneRelation getRelation(glm::vec3 point) const;
+	std::optional<DistAndPosition> getRayIntersectPosition(const Ray &) const;
+
+	static bool isIntersect(PlaneRelation a, PlaneRelation b);
 };
-- 
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