private static void AdjustVelocities(Actor actor1, Actor actor2) {
if(actor1.Mass <= 0f || actor2.Mass <= 0f) {
return;
}
Vector2 collisionNormal = Vector2.Normalize(actor2.Position - actor1.Position);
Vector2 collisionTangent = new Vector2(-collisionNormal.Y, collisionNormal.X);
float velocityNormal1 = Vector2.Dot(actor1.Velocity, collisionNormal);
float velocityTangent1 = Vector2.Dot(actor1.Velocity, collisionNormal);
float velocityNormal2 = Vector2.Dot(actor2.Velocity, collisionNormal);
float velocityTangent2 = Vector2.Dot(actor2.Velocity, collisionTangent);
float velocityNormal1New = ((velocityNormal1 * (actor1.Mass - actor2.Mass))
+ (2f * actor2.Mass * velocityNormal2)) / (actor1.Mass + actor2.Mass);
float velocityNormal2New = ((velocityNormal2 * (actor2.Mass - actor1.Mass))
+ (2f * actor1.Mass * velocityNormal1)) / (actor1.Mass + actor2.Mass);
actor1.Velocity = (velocityNormal1New * collisionNormal) +(velocityTangent1 * collisionTangent);
actor2.Velocity = (velocityNormal2New * collisionNormal) +(velocityTangent2 * collisionTangent);
}
public static bool CircleLineCollide(Vector2 center, float radius,Vector2 lineStart, Vector2 lineEnd, ref CircleLineCollisionResult result) {
Vector2 AC = center - lineStart;
Vector2 AB = lineEnd - lineStart;
float ab2 = AB.LengthSquared();
if(ab2 <= 0f) {
return false;
}
float acab = Vector2.Dot(AC, AB);
float t = acab / ab2;
if(t < 0.0f) {
t = 0.0f;//点Hが点Aの場所になる
} else if(t > 1.0f) {
t = 1.0f;//点Hが点Bの場所になる
}
result.Point = lineStart + t * AB;
result.Normal = center - result.Point;
float h2 = result.Normal.LengthSquared();
float r2 = radius * radius;
if(h2 > r2) {
result.Collision = false;
} else {
result.Normal.Normalize();
result.Distance = (radius - (center - result.Point).Length());
result.Collision = true;
}
return result.Collision;
} きれいに書いてみたかったのでTEXを使ってみた。環境をつくるのがめんどい。図はGRAPESを使ってみました。使い方が独特だけど、簡単に図形がかけてよい感じ。
public static bool LineLineIntersect(Vector2 a, Vector2 b,Vector2 c, Vector2 d, out Vector2 point) {
point = Vector2.Zero;
double r, s;
double denominator = (b.X - a.X) * (d.Y - c.Y) - (b.Y - a.Y)*(d.X - c.X);
//分母が０の場合平行
if(denominator == 0) {
return false;
}
double numeratorR = (a.Y - c.Y) * (d.X - c.X) - (a.X - c.X)*(d.Y - c.Y);
r = numeratorR / denominator;
double numeratorS = (a.Y - c.Y)*(b.X - a.X) - (a.X - c.X) * (b.Y - a.Y);
s = numeratorS / denominator;
//交差しない
if(r < 0 || r > 1 || s<0 || s > 1) {
return false;
}
point.X = (float)(a.X + (r * (b.X - a.X)));
point.Y = (float)(a.Y + (r * (b.Y - a.Y)));
return true;
}
private void MoveWorld(float elapsedTime) {
Vector2 point = Vector2.Zero;
for(int i = 0; i < actors.Count; ++i) {
if(actors[i].Dead) {
continue;
}
Vector2 movement = actors[i].Velocity * elapsedTime;
if(actors[i].CollidedThisFrame == false) {
//Actorと
movement = MoveAndCollide(actors[i], movement);
}
actors[i].Position += movement;
//壁と
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)) {
float vn = Vector2.Dot(actors[i].Velocity, result.Normal);
actors[i].Velocity -= (2.0f * vn) * result.Normal;
actors[i].Position += result.Normal * result.Distance;
}
}
}
}
}
for(int w = 0; w < walls.Length / 2; ++w) {
Collision.CircleLineCollisionResult result = new collision.CircleLineCollisionResult();
if(Collision.CircleLineCollide(actors[i].Position,actors[i].Radius, walls[w * 2], walls[w * 2 + 1],ref result)) {
float vn = Vector2.Dot(actors[i].Velocity, result.Normal);
actors[i].Velocity -= (2.0f * vn) * result.Normal;
actors[i].Position += result.Normal * result.Distance;
}
}
Vector2 forward = new Vector2((float)Math.Sin(Rotation),-(float)Math.Cos(Rotation)); Vector2 right = new Vector2(-forward.Y, forward.X);Actorオブジェクトが持っているプロパティーRotation（角度）を使って。
float angleDiff = (float)Math.Acos(Vector2.Dot(wantedForward, forward));内積の式の変形より、スティックで入力された角度と、現在のforwardとのなす角を出す。
float facing = (Vector2.Dot(wantedForward, right) > 0f) ? 1f : -1f;内積の符号を調べることで、なす角が鋭角か鈍角かを調べることができる。
if(angleDiff > 0f) {
Rotation += Math.Min(angleDiff, facing * elapsedTime * rotationRadiansPerSecond);
}
Velocity += leftStick * (elapsedTime * speed);
if(Velocity.Length() > velocityLengthMaximum) {
Velocity = Vector2.Normalize(Velocity) * velocityLengthMaximum;
} angleDiffの範囲は０からπまで、０は動いていないのでそれを省く
１秒当たりの向きを変えられる量、速度など１秒当たりで決める。
elapsedTimeは経過時間なので掛けることで移動量などが計算できる。
for(int i = 0; i < menuEntries.Count; i++) {}
のかたちで書くことができる。
bool UpdateTransition(GameTime gameTime, TimeSpan time, int direction) {
float transitionDelta;
if(time == TimeSpan.Zero) {
transitionDelta = 1;
} else {
transitionDelta = (float)(gameTime.ElapsedGameTime.TotalMilliseconds / time.TotalMilliseconds);
}
transitionPosition += transitionDelta * direction;
if((transitionPosition <= 0) || (transitionPosition >= 1)) {
transitionPosition = MathHelper.Clamp(transitionPosition, 0, 1);
return false;
}
return true;
}
これによって計算されたプロパティTransitionPositionを表示位置に適用する。
while(screensToUpdate.Count > 0) {
//GameScreenを後ろから順番に参照する
GameScreen screen = screensToUpdate[screensToUpdate.Count - 1];
screensToUpdate.RemoveAt(screensToUpdate.Count - 1);
screen.Update(gameTime, otherScreenHasFocus, coveredByOtherScreen);
if(!otherScreenHasFocus) {
screen.HandleInput(input);
otherScreenHasFocus = true;
}
//もしGameScreenがポップアップタイプでなかったら、次のスクリーンは coveredByOthierScreen=trueになる。（覆い隠されている）
if(!screen.IsPopup) {
coveredByOtherScreen = true;
}
}
