SCNCylinder上的设置内容（图像）被反转（翻转）

Question

我尝试使用以下代码在SCNCylinder对象上渲染图像：

    let coinGeometry = SCNCylinder(radius: 50, height: 55)
    coinNode = SCNNode(geometry: coinGeometry)
    coinNode.position = SCNVector3Make(0.0, 25.0, 25.0)
    coinScene.rootNode.addChildNode(coinNode)

   //Add image on cylinder shape
    let frontFacingImageMaterial = SCNMaterial()
    frontFacingImageMaterial.diffuse.contents = UIImage(named: "map")
    frontFacingImageMaterial.specular.contents = UIColor.blueColor()
    frontFacingImageMaterial.shininess = 5.0
    coinGeometry.firstMaterial = frontFacingImageMaterial

在气缸上，此图像显示为反转（翻转）。我该如何解决？

由于

Answer 1

来自How to flip UIImage horizontally?：

UIImage* sourceImage = [UIImage imageNamed:@"whatever.png"];
UIImage* flippedImage = [UIImage imageWithCGImage:sourceImage.CGImage 
                                        scale:sourceImage.scale
                           orientation:UIImageOrientationUpMirrored];

所以在Swift中，类似于：

if let originalImage = UIImage(named: "map") {
    let materialImage = UIImage(CGImage: originalImage.CGImage!, 
                                scale: originalImage.scale, 
                                orientation: .UpMirrored)
}

Answer 2

不要翻转原始图像数据，只需翻转它映射到几何体上的方式。将frontFacingImageMaterial.diffuse.contentsTransform设置为翻转X或Y的矩阵。