#region File Description
//-----------------------------------------------------------------------------
// ChaseCamera.cs
//
// Microsoft XNA Community Game Platform
// Copyright (C) Microsoft Corporation. All rights reserved.
//-----------------------------------------------------------------------------
#endregion
#region Using Statements
using System;
using System.Collections.Generic;
using Microsoft.Xna.Framework;
#endregion
namespace Game1
{
public class ChaseCamera
{
private Quaternion q;
int cameraMode = 2;
public int Mode
{
get { return cameraMode; }
}
#region Chased object properties (set externally each frame)
/// <summary>
/// Position of object being chased.
/// </summary>
public Vector3 ChasePosition
{
get { return chasePosition; }
set { chasePosition = value; }
}
private Vector3 chasePosition;
/// <summary>
/// Direction the chased object is facing.
/// </summary>
public Vector3 ChaseDirection
{
get { return chaseDirection; }
set { chaseDirection = value; }
}
private Vector3 chaseDirection;
/// <summary>
/// Chased object's Up vector.
/// </summary>
public Vector3 Up
{
get { return up; }
set { up = value; }
}
private Vector3 up = Vector3.Up;
#endregion
#region Desired camera positioning (set when creating camera or changing view)
/// <summary>
/// Desired camera position in the chased object's coordinate system.
/// </summary>
public Vector3 DesiredPositionOffset
{
get { return desiredPositionOffset; }
set { desiredPositionOffset = value; }
}
private Vector3 desiredPositionOffset = new Vector3(0, 2.0f, 2.0f);
/// <summary>
/// Desired camera position in world space.
/// </summary>
public Vector3 DesiredPosition
{
get
{
// Ensure correct value even if update has not been called this frame
UpdateWorldPositions();
return desiredPosition;
}
}
private Vector3 desiredPosition;
/// <summary>
/// Look at point in the chased object's coordinate system.
/// </summary>
public Vector3 LookAtOffset
{
get { return lookAtOffset; }
set { lookAtOffset = value; }
}
private Vector3 lookAtOffset = new Vector3(0, 2.8f, 0);
/// <summary>
/// Look at point in world space.
/// </summary>
public Vector3 LookAt
{
get
{
// Ensure correct value even if update has not been called this frame
UpdateWorldPositions();
return lookAt;
}
}
private Vector3 lookAt;
#endregion
#region Camera physics (typically set when creating camera)
/// <summary>
/// Physics coefficient which controls the influence of the camera's position
/// over the spring force. The stiffer the spring, the closer it will stay to
/// the chased object.
/// </summary>
public float Stiffness
{
get { return stiffness; }
set { stiffness = value; }
}
private float stiffness = 1800.0f;
/// <summary>
/// Physics coefficient which approximates internal friction of the spring.
/// Sufficient damping will prevent the spring from oscillating infinitely.
/// </summary>
public float Damping
{
get { return damping; }
set { damping = value; }
}
private float damping = 600.0f;
/// <summary>
/// Mass of the camera body. Heaver objects require stiffer springs with less
/// damping to move at the same rate as lighter objects.
/// </summary>
public float Mass
{
get { return mass; }
set { mass = value; }
}
private float mass = 50.0f;
#endregion
#region Current camera properties (updated by camera physics)
/// <summary>
/// Position of camera in world space.
/// </summary>
public Vector3 Position
{
get { return position; }
}
private Vector3 position;
/// <summary>
/// Velocity of camera.
/// </summary>
public Vector3 Velocity
{
get { return velocity; }
}
private Vector3 velocity;
#endregion
#region Perspective properties
/// <summary>
/// Perspective aspect ratio. Default value should be overriden by application.
/// </summary>
public float AspectRatio
{
get { return aspectRatio; }
set { aspectRatio = value; }
}
private float aspectRatio = 4.0f / 3.0f;
/// <summary>
/// Perspective field of view.
/// </summary>
public float FieldOfView
{
get { return fieldOfView; }
set { fieldOfView = value; }
}
private float fieldOfView = MathHelper.ToRadians(45.0f);
/// <summary>
/// Distance to the near clipping plane.
/// </summary>
public float NearPlaneDistance
{
get { return nearPlaneDistance; }
set { nearPlaneDistance = value; }
}
private float nearPlaneDistance = 1.0f;
/// <summary>
/// Distance to the far clipping plane.
/// </summary>
public float FarPlaneDistance
{
get { return farPlaneDistance; }
set { farPlaneDistance = value; }
}
private float farPlaneDistance = 10000.0f;
#endregion
#region Matrix properties
/// <summary>
/// View transform matrix.
/// </summary>
public Matrix View
{
get { return view; }
}
private Matrix view;
/// <summary>
/// Projecton transform matrix.
/// </summary>
public Matrix Projection
{
get { return projection; }
}
private Matrix projection;
#endregion
#region Methods
/// <summary>
/// Rebuilds object space values in world space. Invoke before publicly
/// returning or privately accessing world space values.
/// </summary>
private void UpdateWorldPositions()
{
// Construct a matrix to transform from object space to worldspace
Matrix transform = Matrix.Identity;
transform.Forward = ChaseDirection;
transform.Up = Up;
transform.Right = Vector3.Cross(Up, ChaseDirection);
// Calculate desired camera properties in world space
if (cameraMode == 0)
{
desiredPosition = ChasePosition +
Vector3.TransformNormal(DesiredPositionOffset, transform);
lookAt = ChasePosition +
Vector3.TransformNormal(LookAtOffset, transform);
}
if (cameraMode == 2)
{
desiredPosition = ChasePosition +
Vector3.TransformNormal(DesiredPositionOffset, transform);
lookAt = ChasePosition + 10000 * ChaseDirection;
}
}
public void UpdateNewCamera(float xFac, float yFac)
{
if (cameraMode != 1)
return;
Matrix transform = Matrix.Identity;
transform.Forward = ChaseDirection;
transform.Up = Up;
transform.Right = Vector3.Cross(Up, ChaseDirection);
Vector3 o = ChasePosition +
Vector3.TransformNormal(DesiredPositionOffset, transform);
Vector3 d = ChasePosition +
Vector3.TransformNormal(LookAtOffset, transform);
view = Matrix.CreateLookAt(o, d, this.Up);
projection = Matrix.CreatePerspectiveFieldOfView(FieldOfView,
AspectRatio, NearPlaneDistance, FarPlaneDistance);
BoundingFrustum f = new BoundingFrustum(this.view * this.projection);
Vector3[] fcorners = new Vector3[8];
f.GetCorners(fcorners);
Vector3 fnx = fcorners[1] - fcorners[0];
Vector3 fny = fcorners[3] - fcorners[0];
Vector3 mousePos = fcorners[0] + (xFac * fnx) + (yFac * fny);
Vector3 mouseDir = mousePos - o;
//mouseDir.Normalize();
desiredPosition = o; // correct, I guess
lookAt = d;
//return;
// plane normal = ChasePosition - o
Vector3 v, v2 = (d - o);
Vector3.Normalize(ref v2, out v);
Plane p = new Plane(v, -Vector3.Dot(v, d));
Ray r = new Ray(o, mouseDir);
float? t = r.Intersects(p);
if (t != null)
{
v = o + (float)t * mouseDir;
v = (v - d);
lookAt = d + v / 2;
//lookAt = ChasePosition + mouseDir;
//lookAt = d;
}
//camera.ChasePosition = ship.Position
}
/// <summary>
/// Rebuilds camera's view and projection matricies.
/// </summary>
private void UpdateMatrices()
{
view = Matrix.CreateLookAt(this.Position, this.LookAt, this.Up);
projection = Matrix.CreatePerspectiveFieldOfView(FieldOfView,
AspectRatio, NearPlaneDistance, FarPlaneDistance);
}
/// <summary>
/// Forces camera to be at desired position and to stop moving. The is useful
/// when the chased object is first created or after it has been teleported.
/// Failing to call this after a large change to the chased object's position
/// will result in the camera quickly flying across the world.
/// </summary>
public void Reset()
{
UpdateWorldPositions();
// Stop motion
velocity = Vector3.Zero;
// Force desired position
position = desiredPosition;
UpdateMatrices();
}
/// <summary>
/// Animates the camera from its current position towards the desired offset
/// behind the chased object. The camera's animation is controlled by a simple
/// physical spring attached to the camera and anchored to the desired position.
/// </summary>
public void Update(GameTime gameTime)
{
if (gameTime == null)
throw new ArgumentNullException("gameTime");
UpdateWorldPositions();
float elapsed = (float)gameTime.ElapsedGameTime.TotalSeconds;
// Calculate spring force
Vector3 stretch = position - desiredPosition;
Vector3 force = -stiffness * stretch - damping * velocity;
// Apply acceleration
Vector3 acceleration = force / mass;
velocity += acceleration * elapsed;
// Apply velocity
position += velocity * elapsed;
UpdateMatrices();
}
#endregion
}
}