/// <summary>
/// Update the marble's position based on momentary velocity.
/// </summary>
/// <param name="deltaVelocity">The average velocity between the last two
/// calls to this method.</param>
/// <param name="deltaTime">The elapsed time between the last two calls to
/// this method.</param>
private void UpdateMovement(Vector3 deltaVelocity, float deltaTime)
{
// Calculate the change in the marble's position
Vector3 deltaPosition = deltaVelocity * deltaTime;
// Before setting the new position, we must make sure it is legal
BoundingSphere nextPosition = this.BoundingSphereTransformed;
nextPosition.Center += deltaPosition;
IntersectDetails nextIntersectDetails = new IntersectDetails();
Maze.GetCollisionDetails(nextPosition, ref nextIntersectDetails, true);
nextPosition.Radius += 1.0f;
// Move the marble
Position += deltaPosition;
// If the floor not straight then we must reposition the marble vertically
Vector3 forwardVecX = Vector3.Transform(normal,
Matrix.CreateRotationZ(-MathHelper.PiOver2));
Vector3 forwardVecZ = Vector3.Transform(normal,
Matrix.CreateRotationX(-MathHelper.PiOver2));
bool isGroundStraight = true;
if (forwardVecX.X != -1 && forwardVecX.X != 0)
{
Position.Y += deltaPosition.X / forwardVecX.X * forwardVecX.Y;
isGroundStraight = false;
}
if (forwardVecZ.X != -1 && forwardVecZ.X != 0)
{
Position.Y += deltaPosition.Z / forwardVecZ.Z * forwardVecZ.Y;
isGroundStraight = false;
}
// If the marble is already inside the floor, we must reposition it
if (isGroundStraight && nextIntersectDetails.IntersectWithGround)
{
Position.Y = nextIntersectDetails.IntersectedGroundTriangle.A.Y +
BoundingSphereTransformed.Radius;
}
// Finally, we "roll" the marble in accordance to its movement
if (BoundingSphereTransformed.Radius != 0)
{
Rotation.Z = deltaPosition.Z / BoundingSphereTransformed.Radius;
Rotation.X = deltaPosition.X / BoundingSphereTransformed.Radius;
}
}
/// <summary>
/// Perform collision checks with the maze.
/// </summary>
protected override void CalculateCollisions()
{
Maze.GetCollisionDetails(BoundingSphereTransformed, ref intersectDetails, false);
if (intersectDetails.IntersectWithWalls)
{
foreach (var triangle in intersectDetails.IntersectedWallTriangle)
{
Axis direction = CollideDirection(triangle);
if ((direction & Axis.X) == Axis.X && (direction & Axis.Z) == Axis.Z)
{
Maze.GetCollisionDetails(BoundingSphereTransformed, ref intersectDetails, true);
}
}
}
}