Shaker/Veldrid/Agg/VectorMath/TrackBallController.cs

/*
Copyright (c) 2018, Lars Brubaker, John Lewin
All rights reserved.

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   and/or other materials provided with the distribution.

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*/

using System;

namespace MatterHackers.VectorMath.TrackBall
{
	public enum TrackBallTransformType { None, Translation, Rotation, Scale };

	public class TrackBallController
	{
		private Matrix4X4 localToScreenTransform;

		private Vector2 mouseDownPosition;

		public Vector2 ScreenCenter { get; set; }

		private Vector2 lastTranslationMousePosition = Vector2.Zero;
		private Vector2 lastScaleMousePosition = Vector2.Zero;

		private readonly WorldView world;

		public TrackBallController(WorldView world, double trackBallRadius = 1)
		{
			mouseDownPosition = new Vector2();
			this.TrackBallRadius = trackBallRadius;

			this.world = world;
		}

		public TrackBallTransformType CurrentTrackingType { get; private set; } = TrackBallTransformType.None;

		public static Vector3 MapMoveToSphere(Vector2 screenCenter, double trackBallRadius, Vector2 startPosition, Vector2 endPosition, bool rotateOnScreenZ)
		{
			if (rotateOnScreenZ)
			{
				var angleToTravel = screenCenter.GetDeltaAngle(startPosition, endPosition);

				// now rotate that position about z in the direction of the screen vector
				var positionOnRotationSphere = Vector3Ex.Transform(new Vector3(1, 0, 0), Matrix4X4.CreateRotationZ(angleToTravel/2));

				return positionOnRotationSphere;
			}
			else
			{
				var deltaFromStartPixels = endPosition - startPosition;
				var deltaOnSurface = new Vector2(deltaFromStartPixels.X / trackBallRadius, deltaFromStartPixels.Y / trackBallRadius);

				var lengthOnSurfaceRadi = deltaOnSurface.Length;

				// get this rotation on the surface of the sphere about y
				var positionAboutY = Vector3Ex.Transform(new Vector3(0, 0, 1), Matrix4X4.CreateRotationY(lengthOnSurfaceRadi));

				// get the angle that this distance travels around the sphere
				var angleToTravel = Math.Atan2(deltaOnSurface.Y, deltaOnSurface.X);

				// now rotate that position about z in the direction of the screen vector
				var positionOnRotationSphere = Vector3Ex.Transform(positionAboutY, Matrix4X4.CreateRotationZ(angleToTravel));

				return positionOnRotationSphere;
			}
		}

		//Mouse down
		public void OnMouseDown(Vector2 mousePosition, Matrix4X4 screenToLocal, TrackBallTransformType trackType = TrackBallTransformType.Rotation)
		{
			//if (currentTrackingType == MouseDownType.None)
			{
				CurrentTrackingType = trackType;
				switch (CurrentTrackingType)
				{
					case TrackBallTransformType.Rotation:
						mouseDownPosition = mousePosition;
						break;

					case TrackBallTransformType.Translation:
						localToScreenTransform = Matrix4X4.Invert(screenToLocal);
						lastTranslationMousePosition = mousePosition;
						break;

					case TrackBallTransformType.Scale:
						lastScaleMousePosition = mousePosition;
						break;

					default:
						throw new NotImplementedException();
				}
			}
		}

		//Mouse drag, calculate rotation
		public void OnMouseMove(Vector2 mousePosition)
		{
			switch (CurrentTrackingType)
			{
				case TrackBallTransformType.Rotation:
					Quaternion activeRotationQuaternion = GetRotationForMove(ScreenCenter, TrackBallRadius, mouseDownPosition, mousePosition, false);

					if (activeRotationQuaternion != Quaternion.Identity)
					{
						mouseDownPosition = mousePosition;
						world.RotationMatrix *= Matrix4X4.CreateRotation(activeRotationQuaternion);
					}

					break;

				case TrackBallTransformType.Translation:
					{
						Vector2 mouseDelta = mousePosition - lastTranslationMousePosition;
						Vector2 scaledDelta = mouseDelta / this.ScreenCenter.X * 4.75;
						var offset = new Vector3(scaledDelta.X, scaledDelta.Y, 0);
						offset = Vector3Ex.TransformPosition(offset, Matrix4X4.Invert(world.RotationMatrix));
						offset = Vector3Ex.TransformPosition(offset, localToScreenTransform);
						world.TranslationMatrix *= Matrix4X4.CreateTranslation(offset);
						lastTranslationMousePosition = mousePosition;
					}
					break;

				case TrackBallTransformType.Scale:
					{
						Vector2 mouseDelta = mousePosition - lastScaleMousePosition;
						double zoomDelta = 1;
						if (mouseDelta.Y < 0)
						{
							zoomDelta = 1 - (-1 * mouseDelta.Y / 100);
						}
						else if (mouseDelta.Y > 0)
						{
							zoomDelta = 1 + (1 * mouseDelta.Y / 100);
						}
						world.Scale *= zoomDelta;
						lastScaleMousePosition = mousePosition;
					}
					break;

				default:
					throw new NotImplementedException();
			}
		}

		public static Quaternion GetRotationForMove(Vector2 screenCenter, double trackBallRadius, Vector2 startPosition, Vector2 endPosition, bool rotateOnZ)
		{
			var activeRotationQuaternion = Quaternion.Identity;

			//Map the point to the sphere
			var moveSpherePosition = MapMoveToSphere(screenCenter, trackBallRadius, startPosition, endPosition, rotateOnZ);

			//Return the quaternion equivalent to the rotation
			//Compute the vector perpendicular to the begin and end vectors
			var rotationStart3D = new Vector3(0, 0, 1);
			if (rotateOnZ)
			{
				rotationStart3D = new Vector3(1, 0, 0);
			}
			Vector3 perp = rotationStart3D.Cross(moveSpherePosition);

			//Compute the length of the perpendicular vector
			double epsilon = 1.0e-5;
			if (perp.Length > epsilon)
			{
				//if its non-zero
				//We're ok, so return the perpendicular vector as the transform after all
				activeRotationQuaternion.X = perp.X;
				activeRotationQuaternion.Y = perp.Y;
				activeRotationQuaternion.Z = perp.Z;
				//In the quaternion values, w is cosine (theta / 2), where theta is the rotation angle
				activeRotationQuaternion.W = -rotationStart3D.Dot(moveSpherePosition);
			}

			return activeRotationQuaternion;
		}

		public void OnMouseUp()
		{
			switch (CurrentTrackingType)
			{
				case TrackBallTransformType.Rotation:
					break;

				case TrackBallTransformType.Translation:
					//currentTranslationMatrix = Matrix4X4.Identity;
					break;

				case TrackBallTransformType.Scale:
					break;

				default:
					throw new NotImplementedException();
			}
			CurrentTrackingType = TrackBallTransformType.None;
		}

		public void OnMouseWheel(int wheelDelta)
		{
			double zoomDelta = 1;
			if (wheelDelta > 0)
			{
				zoomDelta = 1.2;
			}
			else if (wheelDelta < 0)
			{
				zoomDelta = .8;
			}

			world.Scale *= zoomDelta;
		}

		public double TrackBallRadius { get; set; }
	}
}