在不同位置创建的多边形形状

Question

我正试图用鼠标关节在屏幕中心创建一个多边形，非常简单。CircleShape效果很好。此外，鼠标关节的行为很奇怪，我找不到模式。所有代码都在这里的主文件中。我把代码控制在最低限度。

Vector2 vec2Median(List<Vector2> vecs) {
var sum = Vector2(0, 0);
for (final v in vecs) {
sum += v;
}
return sum / vecs.length.toDouble();
}
void main() {
final game = MyGame();
runApp(GameWidget(game: game));
}
class MyGame extends Forge2DGame with MultiTouchDragDetector, HasTappables {
MouseJoint? mouseJoint;
static late BodyComponent grabbedBody;
late Body groundBody;
MyGame() : super(gravity: Vector2(0, -10.0));
@override
Future<void> onLoad() async {
final boundaries = createBoundaries(this); //Adding boundries
boundaries.forEach(add);
groundBody = world.createBody(BodyDef());
final center = screenToWorld(camera.viewport.effectiveSize / 2);
final poly = Polygon([
center + Vector2(0, 0),
center + Vector2(0, 5),
center + Vector2(5, 0),
center + Vector2(5, 5)
], bodyType: BodyType.dynamic);
add(poly);
grabbedBody = poly;
}
@override
bool onDragUpdate(int pointerId, DragUpdateInfo details) {
final mouseJointDef = MouseJointDef()
..maxForce = 3000 * grabbedBody.body.mass * 10 //Not neccerly needed
..dampingRatio = 1
..frequencyHz = 5
..target.setFrom(grabbedBody.body.position)
..collideConnected = false //Maybe set to true
..bodyA = groundBody
..bodyB = grabbedBody.body;
mouseJoint ??= world.createJoint(mouseJointDef) as MouseJoint;
mouseJoint?.setTarget(details.eventPosition.game);
return false;
}
@override
bool onDragEnd(int pointerId, DragEndInfo details) {
if (mouseJoint == null) {
return true;
}
world.destroyJoint(mouseJoint!);
mouseJoint = null;
return false;
}
}
abstract class TappableBodyComponent extends BodyComponent with Tappable {
final Vector2 position;
final BodyType bodyType;
TappableBodyComponent(this.position, {this.bodyType = BodyType.dynamic});
@override
bool onTapDown(_) {
MyGame.grabbedBody = this;
return false;
}
Body tappableBCreateBody(Shape shape) {
final fixtureDef = FixtureDef(shape)
..restitution = 0.8
..density = 1.0
..friction = 0.4;
final bodyDef = BodyDef()
// To be able to determine object in collision
..userData = this
..angularDamping = 0.8
..position = position
..type = bodyType;
return world.createBody(bodyDef)..createFixture(fixtureDef);
}
}
class Polygon extends TappableBodyComponent {
final List<Vector2> vertecies;
Polygon(this.vertecies, {BodyType bodyType = BodyType.dynamic})
: super(vec2Median(vertecies), bodyType: bodyType);
@override
Body createBody() {
final shape = PolygonShape()..set(vertecies);
return tappableBCreateBody(shape);
}
}

tappableBCreateBody封装了Tappable和body创建方法，Polygon是我试图创建的对象，vec2Median返回多边形的中心(按顶点(。

非常感谢！

Answer 1

我认为您必须从顶点中移除center，并且只将其添加为BodyComponent的位置，就像您在Polygon类的超级调用中所做的那样。