Vuforia Swift-对象比例

Question

我从https://github.com/yshrkt/VuforiaSampleSwift下载了带有Swift的示例Vuforia实现。它不能正常工作，但是玩了一点之后我就可以运行它了。 Objective-C中有一些包装。我有一个问题。值为_objectScale = 0.03175f。我认为它是针对一台设备进行硬编码的，但是当我在其他设备上运行它时，目标太小或太大。我需要为每个设备手动调整此值。有人可以告诉我这种价值来自何处吗？我能以某种方式在设备上即时计算它还是从Vuforia库中读取它？

- (id)initWithFrame:(CGRect)frame manager:(VuforiaManager *)manager
{
    self = [super initWithFrame:frame];

    if (self) {
        _manager = manager;
        // Enable retina mode if available on this device
        if (YES == [_manager isRetinaDisplay]) {
            [self setContentScaleFactor:[UIScreen mainScreen].nativeScale];
        }

        // Create the OpenGL ES context
        _context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];

        // The EAGLContext must be set for each thread that wishes to use it.
        // Set it the first time this method is called (on the main thread)
        if (_context != [EAGLContext currentContext]) {
            [EAGLContext setCurrentContext:_context];
        }

        _offTargetTrackingEnabled = NO;
        _objectScale = 0.03175f;

        _nearPlane = 0.01;
        _farPlane = 5;

        [self initRendering];
    }

    return self;
}