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math/matrix3.cpp

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+/* ScummVM - Graphic Adventure Engine
+ *
+ * ScummVM is the legal property of its developers, whose names
+ * are too numerous to list here. Please refer to the COPYRIGHT
+ * file distributed with this source distribution.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include "math/matrix3.h"
+
+namespace Math {
+
+void swap (float &a, float &b) {
+	float c = a; a = b; b = c;
+}
+
+void Matrix<3, 3>::transpose() {
+	swap(operator()(0, 1), operator()(1, 0));
+	swap(operator()(0, 2), operator()(2, 0));
+	swap(operator()(1, 2), operator()(2, 1));
+}
+
+/**
+ * Generates a lookat matrix. For reference, see
+ * https://clb.confined.space/MathGeoLib/nightly/docs/float3x3_LookAt.php
+ */
+void Matrix<3, 3>::buildFromTargetDir(const Math::Vector3d &modelForward, const Math::Vector3d &targetDirection,
+	                              const Math::Vector3d &modelUp, const Math::Vector3d &worldUp) {
+	Math::Vector3d modelRight = Math::Vector3d::crossProduct(modelUp, modelForward);
+	modelRight.normalize();
+	Math::Vector3d worldRight = Math::Vector3d::crossProduct(worldUp, targetDirection);
+	worldRight.normalize();
+	Math::Vector3d perpWorldUp = Math::Vector3d::crossProduct(targetDirection, worldRight);
+	perpWorldUp.normalize();
+
+	Math::Matrix3 m1;
+	m1.getRow(0) << worldRight.x() << worldRight.y() << worldRight.z();
+	m1.getRow(1) << perpWorldUp.x() << perpWorldUp.y() << perpWorldUp.z();
+	m1.getRow(2) << targetDirection.x() << targetDirection.y() << targetDirection.z();
+	m1.transpose();
+
+	Math::Matrix3 m2;
+	m2.getRow(0) << modelRight.x() << modelRight.y() << modelRight.z();
+	m2.getRow(1) << modelUp.x() << modelUp.y() << modelUp.z();
+	m2.getRow(2) << modelForward.x() << modelForward.y() << modelForward.z();
+
+	this->operator=(m1 * m2);
+}
+
+
+} // end of namespace Math