Question

升级到cocos2d-iphone 2.0版后，我遇到了绘制对象的坐标问题。据我所知，我已正确升级了所有模板，但仍存在问题。例如，在“Learning Cocos2D”一书（box2D第10章）中，我已经实现了几个简单的方法来创建第一个createGround和createBoxAtLocation。第一个方法是从init调用的，如下所示：

- (void)createGround {
    CGSize winSize = [[CCDirector sharedDirector] winSize];     

    // Set up the Box2D coordinates that correspond to the four corners of the ground boundary
    float32 margin = 10.0f;
    b2Vec2 lowerLeft = b2Vec2(margin/PTM_RATIO, margin/PTM_RATIO);
    b2Vec2 lowerRight = b2Vec2((winSize.width-margin)/PTM_RATIO, margin/PTM_RATIO);
    b2Vec2 upperRight = b2Vec2((winSize.width-margin)/PTM_RATIO,
                           (winSize.height-margin)/PTM_RATIO);
    b2Vec2 upperLeft = b2Vec2(margin/PTM_RATIO,
                          (winSize.height-margin)/PTM_RATIO);
    // Define the static container body, which will provide the collisions at screen borders.
    b2BodyDef screenBorderDef;
    screenBorderDef.position.Set(0, 0);
    b2Body* screenBorderBody = world->CreateBody(&screenBorderDef);
    b2EdgeShape screenBorderShape;

    // Create fixtures for the four borders (the border shape is re-used)
    screenBorderShape.Set(lowerLeft, lowerRight);
    screenBorderBody->CreateFixture(&screenBorderShape, 0);
    screenBorderShape.Set(lowerRight, upperRight);
    screenBorderBody->CreateFixture(&screenBorderShape, 0);
    screenBorderShape.Set(upperRight, upperLeft);
    screenBorderBody->CreateFixture(&screenBorderShape, 0);
    screenBorderShape.Set(upperLeft, lowerLeft);
    screenBorderBody->CreateFixture(&screenBorderShape, 0);
}

这应该在屏幕边缘绘制一个绿色边界，边距为10点。但是，我只能在底部和左边看到绿色边界。顶部边缘和右边缘分别以屏幕高度和宽度的2倍绘制。

在同一个Box2D示例中，将在用户触摸屏幕的位置绘制一个框。当用户触摸屏幕时，将使用触摸位置调用createBoxAtLocation方法。触摸位置坐标位于cocos2d点坐标中，并且在您期望的范围内。下面是createBoxAtLocation方法：

- (void)createBoxAtLocation:(CGPoint)location
               withSize:(CGSize)size
{

    // First create a body
    b2BodyDef bodyDef;
    bodyDef.type = b2_dynamicBody;                      // This box is a dynamic body (movement handled by box2d)
    bodyDef.position = b2Vec2(location.x/PTM_RATIO,     // convert the point location to meters location
                          location.y/PTM_RATIO);
    bodyDef.allowSleep = false;
    b2Body *body = world->CreateBody(&bodyDef);

    // Now create one or more fixtures to add to the body.
    // To do this, you must first create a shape. In this case, we are creating a square box
    b2PolygonShape shape;
    shape.SetAsBox(size.width/2/PTM_RATIO, size.height/2/PTM_RATIO);    // SetAsBox takes half dimensions as parameters

    b2FixtureDef fixtureDef;
    fixtureDef.shape = &shape;
    fixtureDef.density = 1.0;           // set density. The higher the number, the heavier it is

    body->CreateFixture(&fixtureDef);
}

例如，如果触摸位置是193,190.5的点坐标（在iphone视网膜显示器上），则createBoxAtLocation方法将在点坐标386,381处绘制一个框，即使location.x = 193和location.y = 190.5。请注意，bodyDef.position的box2d坐标为3.86,3.81，因为PTM_RATIO为50。

我还可以说当我运行模拟器并选择iphone（非视网膜）作为硬件时，会在适当的位置创建框，createGround会在屏幕空间内生成适当的边界。我还可以说代码识别所有设备的正确尺寸屏幕（例如cocos2d打印出cocos2d：表面尺寸：iphone的480x320和cocos2d：iphone 3.5视网膜的表面尺寸：960x640）。最后，我运行了调试器并深入到绘图程序中。据我所知和理解，绘图程序已知正确的box2d坐标。但是这个盒子只是以比视网膜显示器的2倍的坐标显示。

我怀疑createGround的问题和createBoxAtLocation的问题都是一样的。我确信有一个简单的解决方案，但我无法弄清楚。有什么建议？

使用cocos2d-iphone版本2.0，Box2D绘图的因子为2

0 个答案: