Desktop/Dev/Cameras/Cameras/CameraSpring.cs

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using System;
using Microsoft.Xna.Framework;

namespace Mindshifter
{
    public sealed class CameraSpring
    {
        private Vector3     mOrigin;
        private Vector3     mPosition;
        private Vector3     mVelocity;

        private float       mStiffness;
        private float       mDamping;

        public Vector3 Origin
        {
            get { return mOrigin; }
            set { mOrigin = value; }
        }

        public Vector3 Position
        {
            get { return mPosition; }
        }

        public Vector3 Velocity
        {
            get { return mVelocity; }
        }

        public float Stiffness
        {
            get { return mStiffness; }
            set { mStiffness = value; }
        }

        public float Damping
        {
            get { return mDamping; }
            set { mDamping = value; }
        }

        public CameraSpring()
        {
            mStiffness = 36f;
            mDamping = 12f;
        }

        public void Update(float elapsed)
        {
            Vector3 stretch = mPosition - mOrigin;
            Vector3 acceleration = -mStiffness * stretch - mDamping * mVelocity;
            mVelocity += acceleration * elapsed;
            mPosition += mVelocity * elapsed;
        }
    }
}

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