/// <summary>
/// Move all of the actors in the world.
/// </summary>
/// <param name="elapsedTime">The amount of elapsed time, in seconds.</param>
private void MoveWorld(float elapsedTime)
{
Vector2 point = Vector2.Zero;
// move each actor
for (int i = 0; i < actors.Count; ++i)
{
if (actors[i].Dead)
{
continue;
}
// determine how far they are going to move
Vector2 movement = actors[i].Velocity * elapsedTime;
// only allow actors that have not collided yet this frame to collide
// -- otherwise, objects can "double-hit" and trade their momentum fast
if (actors[i].CollidedThisFrame == false)
{
movement = MoveAndCollide(actors[i], movement);
}
// determine the new position
actors[i].Position += movement;
// determine if their new position taks them through a wall
for (int w = 0; w < walls.Length / 2; ++w)
{
if (actors[i] is Projectile)
{
if (Collision.LineLineIntersect(actors[i].Position,
actors[i].Position - movement, walls[w * 2],
walls[w * 2 + 1], out point))
{
actors[i].Touch(actors[0]);
}
}
else
{
Collision.CircleLineCollisionResult result =
new Collision.CircleLineCollisionResult();
if (Collision.CircleLineCollide(actors[i].Position,
actors[i].Radius, walls[w * 2], walls[w * 2 + 1],
ref result))
{
// if a non-projectile hits a wall, bounce slightly
float vn = Vector2.Dot(actors[i].Velocity, result.Normal);
actors[i].Velocity -= (2.0f * vn) * result.Normal;
actors[i].Position += result.Normal * result.Distance;
}
}
}
}
}
/// <summary>
/// Move all of the actors in the world.
/// </summary>
/// <param name="elapsedTime">The amount of elapsed time, in seconds.</param>
private void MoveWorld(float elapsedTime)
{
Vector2 point = Vector2.Zero;
// move each actor
for (int i = 0; i < actors.Count; ++i)
{
if (actors[i].Dead)
{
continue;
}
// determine how far they are going to move
Vector2 movement = actors[i].Velocity * elapsedTime;
// only allow actors that have not collided yet this frame to collide
// -- otherwise, objects can "double-hit" and trade their momentum fast
if (actors[i].CollidedThisFrame == false)
{
movement = MoveAndCollide(actors[i], movement);
}
// determine the new position
actors[i].Position += movement;
// determine if their new position taks them through a wall
for (int w = 0; w < walls.Length / 2; ++w)
{
if (actors[i] is Projectile)
{
if (Collision.LineLineIntersect(actors[i].Position,
actors[i].Position - movement, walls[w * 2],
walls[w * 2 + 1], out point))
{
actors[i].Touch(actors[0]);
}
}
else
{
Collision.CircleLineCollisionResult result =
new Collision.CircleLineCollisionResult();
if (Collision.CircleLineCollide(actors[i].Position,
actors[i].Radius, walls[w * 2], walls[w * 2 + 1],
ref result))
{
// if a non-projectile hits a wall, bounce slightly
float vn = Vector2.Dot(actors[i].Velocity, result.Normal);
actors[i].Velocity -= (2.0f * vn) * result.Normal;
actors[i].Position += result.Normal * result.Distance;
}
}
}
}
}
/// <summary>
/// Find a valid point for the actor to spawn.
/// </summary>
/// <param name="actor">The actor to find a location for.</param>
/// <remarks>This query is not bounded, which would be needed in a more complex
/// game with a likelihood of no valid spawn locations.</remarks>
/// <returns>A valid location for the user to spawn.</returns>
public Vector2 FindSpawnPoint(Actor actor)
{
if (actor == null)
{
throw new ArgumentNullException("actor");
}
Vector2 spawnPoint;
float radius = actor.Radius;
// fudge the radius slightly so we're not right on top of another actor
if (actor is Ship)
{
radius *= 2f;
}
else
{
radius *= 1.1f;
}
radius = (float)Math.Ceiling(radius);
Vector2 spawnMinimum = new Vector2(
safeDimensions.X + radius,
safeDimensions.Y + radius);
Vector2 spawnDimensions = new Vector2(
(float)Math.Floor(safeDimensions.Width - 2f * radius),
(float)Math.Floor(safeDimensions.Height - 2f * radius));
Vector2 spawnMaximum = spawnMinimum + spawnDimensions;
Collision.CircleLineCollisionResult result =
new Collision.CircleLineCollisionResult();
bool valid = true;
while (true)
{
valid = true;
// generate a new spawn point
spawnPoint = new Vector2(
spawnMinimum.X + spawnDimensions.X * (float)random.NextDouble(),
spawnMinimum.Y + spawnDimensions.Y * (float)random.NextDouble());
if ((spawnPoint.X < spawnMinimum.X) ||
(spawnPoint.Y < spawnMinimum.Y) ||
(spawnPoint.X > spawnMaximum.X) ||
(spawnPoint.Y > spawnMaximum.Y))
{
continue;
}
// if we don't collide, then one is good enough
if (actor.Collidable == false)
{
break;
}
// check against the walls
if (valid == true)
{
for (int wall = 0; wall < walls.Length / 2; wall++)
{
if (Collision.CircleLineCollide(spawnPoint, radius,
walls[wall * 2], walls[wall * 2 + 1], ref result))
{
valid = false;
break;
}
}
}
// check against all other actors
if (valid == true)
{
foreach (Actor checkActor in actors)
{
if ((actor == checkActor) || checkActor.Dead)
{
continue;
}
if (Collision.CircleCircleIntersect(checkActor.Position,
checkActor.Radius, spawnPoint, radius))
{
valid = false;
break;
}
}
}
// if we have gotten this far, then the spawn point is good
if (valid == true)
{
break;
}
}
return spawnPoint;
}
/// <summary>
/// Find a valid point for the actor to spawn.
/// </summary>
/// <param name="actor">The actor to find a location for.</param>
/// <remarks>This query is not bounded, which would be needed in a more complex
/// game with a likelihood of no valid spawn locations.</remarks>
/// <returns>A valid location for the user to spawn.</returns>
public Vector2 FindSpawnPoint(Actor actor)
{
if (actor == null)
{
throw new ArgumentNullException("actor");
}
Vector2 spawnPoint;
float radius = actor.Radius;
// fudge the radius slightly so we're not right on top of another actor
if (actor is Ship)
{
radius *= 2f;
}
else
{
radius *= 1.1f;
}
radius = (float)Math.Ceiling(radius);
Vector2 spawnMinimum = new Vector2(
safeDimensions.X + radius,
safeDimensions.Y + radius);
Vector2 spawnDimensions = new Vector2(
(float)Math.Floor(safeDimensions.Width - 2f * radius),
(float)Math.Floor(safeDimensions.Height - 2f * radius));
Vector2 spawnMaximum = spawnMinimum + spawnDimensions;
Collision.CircleLineCollisionResult result =
new Collision.CircleLineCollisionResult();
bool valid = true;
while (true)
{
valid = true;
// generate a new spawn point
spawnPoint = new Vector2(
spawnMinimum.X + spawnDimensions.X * (float)random.NextDouble(),
spawnMinimum.Y + spawnDimensions.Y * (float)random.NextDouble());
if ((spawnPoint.X < spawnMinimum.X) ||
(spawnPoint.Y < spawnMinimum.Y) ||
(spawnPoint.X > spawnMaximum.X) ||
(spawnPoint.Y > spawnMaximum.Y))
{
continue;
}
// if we don't collide, then one is good enough
if (actor.Collidable == false)
{
break;
}
// check against the walls
if (valid == true)
{
for (int wall = 0; wall < walls.Length / 2; wall++)
{
if (Collision.CircleLineCollide(spawnPoint, radius,
walls[wall * 2], walls[wall * 2 + 1], ref result))
{
valid = false;
break;
}
}
}
// check against all other actors
if (valid == true)
{
foreach (Actor checkActor in actors)
{
if ((actor == checkActor) || checkActor.Dead)
{
continue;
}
if (Collision.CircleCircleIntersect(checkActor.Position,
checkActor.Radius, spawnPoint, radius))
{
valid = false;
break;
}
}
}
// if we have gotten this far, then the spawn point is good
if (valid == true)
{
break;
}
}
return(spawnPoint);
}
