From 097613f34bb0ff82beb3d6da53d85c8e658f774f Mon Sep 17 00:00:00 2001
From: GeorgH93 <git@georgh93.eu>
Date: Sun, 31 Jan 2021 03:28:21 +0100
Subject: [PATCH] Add Frustum class

---
 openVulkanoCpp/Math/Frustum.hpp | 141 ++++++++++++++++++++++++++++++++
 1 file changed, 141 insertions(+)
 create mode 100644 openVulkanoCpp/Math/Frustum.hpp

diff --git a/openVulkanoCpp/Math/Frustum.hpp b/openVulkanoCpp/Math/Frustum.hpp
new file mode 100644
index 0000000..0526b55
--- /dev/null
+++ b/openVulkanoCpp/Math/Frustum.hpp
@@ -0,0 +1,141 @@
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#pragma once
+
+#include "Math.hpp"
+
+namespace openVulkanoCpp::Math
+{
+	class Frustum
+	{
+		enum Planes
+		{
+			LEFT = 0,
+			RIGHT,
+			BOTTOM,
+			TOP,
+			NEAR,
+			FAR,
+			COUNT,
+			COMBINATIONS = COUNT * (COUNT - 1) / 2
+		};
+
+	public:
+		Frustum()
+		{}
+
+		// m = ProjectionMatrix * ViewMatrix
+		Frustum(Math::Matrix4f m)
+		{
+			m = Math::Utils::transpose(m);
+			m_planes[LEFT] =   m[3] + m[0];
+			m_planes[RIGHT] =  m[3] - m[0];
+			m_planes[BOTTOM] = m[3] + m[1];
+			m_planes[TOP] =    m[3] - m[1];
+			m_planes[NEAR] =   m[3] + m[2];
+			m_planes[FAR] =    m[3] - m[2];
+
+			Math::Vector3f crosses[COMBINATIONS] = {
+					Math::Utils::cross(Math::Vector3f(m_planes[LEFT]),   Math::Vector3f(m_planes[RIGHT])),
+					Math::Utils::cross(Math::Vector3f(m_planes[LEFT]),   Math::Vector3f(m_planes[BOTTOM])),
+					Math::Utils::cross(Math::Vector3f(m_planes[LEFT]),   Math::Vector3f(m_planes[TOP])),
+					Math::Utils::cross(Math::Vector3f(m_planes[LEFT]),   Math::Vector3f(m_planes[NEAR])),
+					Math::Utils::cross(Math::Vector3f(m_planes[LEFT]),   Math::Vector3f(m_planes[FAR])),
+					Math::Utils::cross(Math::Vector3f(m_planes[RIGHT]),  Math::Vector3f(m_planes[BOTTOM])),
+					Math::Utils::cross(Math::Vector3f(m_planes[RIGHT]),  Math::Vector3f(m_planes[TOP])),
+					Math::Utils::cross(Math::Vector3f(m_planes[RIGHT]),  Math::Vector3f(m_planes[NEAR])),
+					Math::Utils::cross(Math::Vector3f(m_planes[RIGHT]),  Math::Vector3f(m_planes[FAR])),
+					Math::Utils::cross(Math::Vector3f(m_planes[BOTTOM]), Math::Vector3f(m_planes[TOP])),
+					Math::Utils::cross(Math::Vector3f(m_planes[BOTTOM]), Math::Vector3f(m_planes[NEAR])),
+					Math::Utils::cross(Math::Vector3f(m_planes[BOTTOM]), Math::Vector3f(m_planes[FAR])),
+					Math::Utils::cross(Math::Vector3f(m_planes[TOP]),    Math::Vector3f(m_planes[NEAR])),
+					Math::Utils::cross(Math::Vector3f(m_planes[TOP]),    Math::Vector3f(m_planes[FAR])),
+					Math::Utils::cross(Math::Vector3f(m_planes[NEAR]),   Math::Vector3f(m_planes[FAR]))
+			};
+
+			m_points[0] = Intersection<LEFT, BOTTOM, NEAR>(crosses);
+			m_points[1] = Intersection<LEFT, TOP, NEAR>(crosses);
+			m_points[2] = Intersection<RIGHT, BOTTOM, NEAR>(crosses);
+			m_points[3] = Intersection<RIGHT, TOP, NEAR>(crosses);
+			m_points[4] = Intersection<LEFT, BOTTOM, FAR>(crosses);
+			m_points[5] = Intersection<LEFT, TOP, FAR>(crosses);
+			m_points[6] = Intersection<RIGHT, BOTTOM, FAR>(crosses);
+			m_points[7] = Intersection<RIGHT, TOP, FAR>(crosses);
+
+		}
+
+		// http://iquilezles.org/www/articles/frustumcorrect/frustumcorrect.htm
+		bool IsBoxVisible(const Math::Vector3f& minp, const Math::Vector3f& maxp) const
+		{ // http://iquilezles.org/www/articles/frustumcorrect/frustumcorrect.htm
+			// check box outside/inside of frustum
+			for (int i = 0; i < COUNT; i++)
+			{
+				if ((Math::Utils::dot(m_planes[i], Math::Vector4f(minp.x, minp.y, minp.z, 1.0f)) < 0.0) &&
+					(Math::Utils::dot(m_planes[i], Math::Vector4f(maxp.x, minp.y, minp.z, 1.0f)) < 0.0) &&
+					(Math::Utils::dot(m_planes[i], Math::Vector4f(minp.x, maxp.y, minp.z, 1.0f)) < 0.0) &&
+					(Math::Utils::dot(m_planes[i], Math::Vector4f(maxp.x, maxp.y, minp.z, 1.0f)) < 0.0) &&
+					(Math::Utils::dot(m_planes[i], Math::Vector4f(minp.x, minp.y, maxp.z, 1.0f)) < 0.0) &&
+					(Math::Utils::dot(m_planes[i], Math::Vector4f(maxp.x, minp.y, maxp.z, 1.0f)) < 0.0) &&
+					(Math::Utils::dot(m_planes[i], Math::Vector4f(minp.x, maxp.y, maxp.z, 1.0f)) < 0.0) &&
+					(Math::Utils::dot(m_planes[i], Math::Vector4f(maxp.x, maxp.y, maxp.z, 1.0f)) < 0.0))
+				{
+					return false;
+				}
+			}
+
+			// check frustum outside/inside box
+			int out;
+			out = 0;
+			for (int i = 0; i < 8; i++) out += ((m_points[i].x > maxp.x) ? 1 : 0);
+			if (out == 8) return false;
+			out = 0;
+			for (int i = 0; i < 8; i++) out += ((m_points[i].x < minp.x) ? 1 : 0);
+			if (out == 8) return false;
+			out = 0;
+			for (int i = 0; i < 8; i++) out += ((m_points[i].y > maxp.y) ? 1 : 0);
+			if (out == 8) return false;
+			out = 0;
+			for (int i = 0; i < 8; i++) out += ((m_points[i].y < minp.y) ? 1 : 0);
+			if (out == 8) return false;
+			out = 0;
+			for (int i = 0; i < 8; i++) out += ((m_points[i].z > maxp.z) ? 1 : 0);
+			if (out == 8) return false;
+			out = 0;
+			for (int i = 0; i < 8; i++) out += ((m_points[i].z < minp.z) ? 1 : 0);
+			if (out == 8) return false;
+
+			return true;
+		}
+
+		bool IsBoxVisible(const Math::Vector4f& minp, const Math::Vector4f& maxp) const
+		{
+			return IsBoxVisible(Math::Vector3f(minp), Math::Vector3f(maxp));
+		}
+
+	private:
+		template<Planes i, Planes j>
+		struct ij2k
+		{
+			enum
+			{
+				k = i * (9 - i) / 2 + j - 1
+			};
+		};
+
+		template<Planes a, Planes b, Planes c>
+		Math::Vector3f Intersection(const Math::Vector3f* crosses) const
+		{
+			float D = Math::Utils::dot(Math::Vector3f(m_planes[a]), crosses[ij2k<b, c>::k]);
+			Math::Vector3f res = Math::Matrix3f(crosses[ij2k<b, c>::k], -crosses[ij2k<a, c>::k], crosses[ij2k<a, b>::k]) *
+					Math::Vector3f(m_planes[a].w, m_planes[b].w, m_planes[c].w);
+			return res * (-1.0f / D);
+		}
+
+		Math::Vector4f m_planes[COUNT];
+		Math::Vector3f m_points[8];
+	};
+}