/// <summary>
/// Load your graphics content.
/// </summary>
protected override void LoadContent()
{
terrain = Content.Load <Model>("terrain");
// The terrain processor attached a HeightMapInfo to the terrain model's
// Tag. We'll save that to a member variable now, and use it to
// calculate the terrain's heights later.
heightMapInfo = terrain.Tag as HeightMapInfo;
if (heightMapInfo == null)
{
string message = "The terrain model did not have a HeightMapInfo " +
"object attached. Are you sure you are using the " +
"TerrainProcessor?";
throw new InvalidOperationException(message);
}
tank.LoadContent(Content);
}
/// <summary>
/// This function is called when the game is Updating in response to user input.
/// It'll move the tank around the heightmap, and update all of the tank's
/// necessary state.
/// </summary>
public void HandleInput(GamePadState currentGamePadState,
KeyboardState currentKeyboardState, HeightMapInfo heightMapInfo)
{
// First, we want to check to see if the tank should turn. turnAmount will
// be an accumulation of all the different possible inputs.
float turnAmount = -currentGamePadState.ThumbSticks.Left.X;
if (currentKeyboardState.IsKeyDown(Keys.A) ||
currentKeyboardState.IsKeyDown(Keys.Left) ||
currentGamePadState.DPad.Left == ButtonState.Pressed)
{
turnAmount += 1;
}
if (currentKeyboardState.IsKeyDown(Keys.D) ||
currentKeyboardState.IsKeyDown(Keys.Right) ||
currentGamePadState.DPad.Right == ButtonState.Pressed)
{
turnAmount -= 1;
}
// clamp the turn amount between -1 and 1, and then use the finished
// value to turn the tank.
turnAmount = MathHelper.Clamp(turnAmount, -1, 1);
facingDirection += turnAmount * TankTurnSpeed;
// Next, we want to move the tank forward or back. to do this,
// we'll create a Vector3 and modify use the user's input to modify the Z
// component, which corresponds to the forward direction.
Vector3 movement = Vector3.Zero;
movement.Z = -currentGamePadState.ThumbSticks.Left.Y;
if (currentKeyboardState.IsKeyDown(Keys.W) ||
currentKeyboardState.IsKeyDown(Keys.Up) ||
currentGamePadState.DPad.Up == ButtonState.Pressed)
{
movement.Z = -1;
}
if (currentKeyboardState.IsKeyDown(Keys.S) ||
currentKeyboardState.IsKeyDown(Keys.Down) ||
currentGamePadState.DPad.Down == ButtonState.Pressed)
{
movement.Z = 1;
}
// next, we'll create a rotation matrix from the direction the tank is
// facing, and use it to transform the vector.
orientation = Matrix.CreateRotationY(FacingDirection);
Vector3 velocity = Vector3.Transform(movement, orientation);
velocity *= TankVelocity;
// Now we know how much the user wants to move. We'll construct a temporary
// vector, newPosition, which will represent where the user wants to go. If
// that value is on the heightmap, we'll allow the move.
Vector3 newPosition = Position + velocity;
if (heightMapInfo.IsOnHeightmap(newPosition))
{
// now that we know we're on the heightmap, we need to know the correct
// height and normal at this position.
Vector3 normal;
heightMapInfo.GetHeightAndNormal(newPosition,
out newPosition.Y, out normal);
// As discussed in the doc, we'll use the normal of the heightmap
// and our desired forward direction to recalculate our orientation
// matrix. It's important to normalize, as well.
orientation.Up = normal;
orientation.Right = Vector3.Cross(orientation.Forward, orientation.Up);
orientation.Right = Vector3.Normalize(orientation.Right);
orientation.Forward = Vector3.Cross(orientation.Up, orientation.Right);
orientation.Forward = Vector3.Normalize(orientation.Forward);
// now we need to roll the tank's wheels "forward." to do this, we'll
// calculate how far they have rolled, and from there calculate how much
// they must have rotated.
float distanceMoved = Vector3.Distance(Position, newPosition);
float theta = distanceMoved / TankWheelRadius;
int rollDirection = movement.Z > 0 ? 1 : -1;
wheelRollMatrix *= Matrix.CreateRotationX(theta * rollDirection);
// once we've finished all computations, we can set our position to the
// new position that we calculated.
position = newPosition;
}
}