init

shared/Trackball.h

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+/*
+ * Copyright (C) 2013-2015 Sergey Kosarevsky (sk@linderdaum.com)
+ * Copyright (C) 2013-2015 Viktor Latypov (vl@linderdaum.com)
+ * Based on Linderdaum Engine http://www.linderdaum.com
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must display the names 'Sergey Kosarevsky' and
+ *    'Viktor Latypov' in the credits of the application, if such credits exist.
+ *    The authors of this work must be notified via email (sk@linderdaum.com) in
+ *    this case of redistribution.
+ *
+ * 3. Neither the name of copyright holders nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS
+ * IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL COPYRIGHT HOLDERS OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#pragma once
+
+#include <numeric>
+
+#include <glm/glm.hpp>
+#include <glm/ext.hpp>
+
+/// Virtual trackball for user interaction with rotations
+class VirtualTrackball
+{
+public:
+	VirtualTrackball() = default;
+
+	/**
+		Get rotation matrix for new mouse point
+	**/
+	glm::mat4 dragTo(glm::vec2 screenPoint, float speed, bool keyPressed)
+	{
+		if (keyPressed && !isDraggingActive_)
+		{
+			startDragging(screenPoint);
+
+			isDraggingActive_ = keyPressed;
+
+			return glm::mat4(1.0f);
+		}
+
+		isDraggingActive_ = keyPressed;
+
+		if (!keyPressed) return glm::mat4(1.0f);
+
+		pointCur_ = projectOnSphere(screenPoint);
+
+		const glm::vec3 direction = pointCur_ - pointPrev_;
+		const float shift = glm::length(direction);
+
+		glm::mat4 rotMatrix = glm::mat4(1.0f);
+
+		if (shift > std::numeric_limits<float>::epsilon())
+		{
+			const glm::vec3 axis = glm::cross( pointPrev_, pointCur_);
+			rotMatrix = glm::rotate(glm::mat4(1.0f), shift * speed, axis);
+		}
+
+		rotationDelta_ = rotMatrix;
+
+		return rotMatrix;
+	}
+
+	const glm::mat4& getRotationDelta() const
+	{
+		return rotationDelta_;
+	};
+
+	/**
+		Get current rotation matrix
+	**/
+	glm::mat4 getRotationMatrix() const
+	{
+		return rotation_ * rotationDelta_;
+	}
+
+private:
+	void startDragging(glm::vec2 screenPoint)
+	{
+		rotation_ = rotation_ * rotationDelta_;
+		rotationDelta_ = glm::mat4(1.0f);
+		pointCur_ = projectOnSphere(screenPoint);
+		pointPrev_ = pointCur_;		
+	}
+
+	glm::vec3 projectOnSphere(glm::vec2 ScreenPoint)
+	{
+		// convert to -1.0...1.0 range
+		glm::vec3 proj(
+			+(2.0f * ScreenPoint.x - 1.0f),
+			-(2.0f * ScreenPoint.y - 1.0f),
+			0.0f
+		);
+
+		const float Length = std::min(glm::length(proj), 1.0f);
+
+		proj.z = sqrtf(1.001f - Length * Length);
+
+		return glm::normalize(proj);
+	}
+	glm::vec3 pointCur_ = glm::vec3(0.0f);
+	glm::vec3 pointPrev_ = glm::vec3(0.0f);
+	glm::mat4 rotation_ = glm::mat4(1.0f);
+	glm::mat4 rotationDelta_ = glm::mat4(1.0f);
+	bool isDraggingActive_ = false;
+};