我有一个将我的世界分成两个的边界，我想允许某些盒子穿过它而其余的则碰撞

Question

这就是我的世界。有两个类：框和边界。 我希望一些盒子物体穿过绿色边界，然后保持反弹。

您可以将绿色边界视为某种过滤器。

 class Boundary {

 // A boundary is a simple rectangle with x,y,width,and height
 float x;
 float y;
 float w;
 float h;

Body b;

Boundary(float x_,float y_, float w_, float h_, float a) {
x = x_;
y = y_;
w = w_;
h = h_;

// Define the polygon
PolygonShape sd = new PolygonShape();
// Figure out the box2d coordinates
float box2dW = box2d.scalarPixelsToWorld(w/2);
float box2dH = box2d.scalarPixelsToWorld(h/2);
// We're just a box
sd.setAsBox(box2dW, box2dH);


// Create the body
BodyDef bd = new BodyDef();
bd.type = BodyType.STATIC;
bd.angle = a;
bd.position.set(box2d.coordPixelsToWorld(x,y));
b = box2d.createBody(bd);

// Attached the shape to the body using a Fixture
b.createFixture(sd,1);
}

// Draw the boundary, if it were at an angle we'd have to do something fancier
void display() {
fill(color(18,220,0));
stroke(0);
strokeWeight(1);
rectMode(CENTER);

float a = b.getAngle();

pushMatrix();
translate(x,y);
rotate(-a);
rect(0,0,w,h);
popMatrix();
}

} 




class Box {

// We need to keep track of a Body and a width and height
Body body;
float w;
float h;

// Constructor
Box(float x_, float y_) {
float x = x_;
float y = y_;
w = 24;
h = 24;
// Add the box to the box2d world
makeBody(new Vec2(x,y),w,h);
}

// This function removes the particle from the box2d world
void killBody() {
box2d.destroyBody(body);
}

boolean contains(float x, float y) {
Vec2 worldPoint = box2d.coordPixelsToWorld(x, y);
Fixture f = body.getFixtureList();
boolean inside = f.testPoint(worldPoint);
return inside;
}

// Drawing the box
void display() {
// We look at each body and get its screen position
Vec2 pos = box2d.getBodyPixelCoord(body);
// Get its angle of rotation
float a = body.getAngle();

rectMode(PConstants.CENTER);
pushMatrix();
translate(pos.x,pos.y);
rotate(a);
fill(175);
stroke(0);
rect(0,0,w,h);
popMatrix();
}


// This function adds the rectangle to the box2d world
 void makeBody(Vec2 center, float w_, float h_) {
// Define and create the body
BodyDef bd = new BodyDef();
bd.type = BodyType.DYNAMIC;
bd.position.set(box2d.coordPixelsToWorld(center));
body = box2d.createBody(bd);

// Define a polygon (this is what we use for a rectangle)
PolygonShape sd = new PolygonShape();
float box2dW = box2d.scalarPixelsToWorld(w_/2);
float box2dH = box2d.scalarPixelsToWorld(h_/2);
sd.setAsBox(box2dW, box2dH);

// Define a fixture
FixtureDef fd = new FixtureDef();
fd.shape = sd;
// Parameters that affect physics
fd.density = 1;
fd.friction = 0.3;
fd.restitution = 0.5;

body.createFixture(fd);
//body.setMassFromShapes();

// Give it some initial random velocity
body.setLinearVelocity(new Vec2(random(-5, 5), random(2, 5)));
body.setAngularVelocity(random(-5, 5));
}

}

Answer 1

免责声明：我不知道box2d或jbox2d

您需要在边界对象和实体上设置过滤类别。因此，例如，您可以将边界对象设置为Filter，categoryBits等于0x0002，然后将不应与边界碰撞的实体设置为Filter {除了0x0002之外，所有位都设置为{1}}。

由于我不知道你的代码是如何组织的，所以这里有一些代码可能会把你推向正确的方向;它无法独立存在：

---

maskBits

（// Make sure you use a different mask for each boundary // if you need to filter separately with different boundaries. public static final int BOUNDARY_CATEGORY = 0x0002 boundaryFilter = new Filter() boundaryFilter.categoryBits = BOUNDARY_CATEGORY boundaryFixture.setFilterData(boundaryFilter) bodyGoingThroughFilter = new Filter() bodyGoingThroughFilter.maskBits = (0xFFFF & (~BOUNDARY_CATEGORY)) bodyGoingThroughFixture.setFilterData(bodyGoingThroughFixture) 内容只应在与要通过边界的实体相关的位置运行。）