Swift-如何更改SCNNode对象的枢轴 [英] Swift - How to change the Pivot of a SCNNode object

问题描述

我已经使用SCNNode对象已有一段时间了，而迷失了Pivot.如何更改SCNNode的枢轴(SCNBox为条形)并将枢轴放置在条形的边缘之一上?

I've been playing with the SCNNode object for a while now and I'm lost with the Pivot. How can I change the pivot of a SCNNode (SCNBox as a bar) and place the pivot on one of the edge of the bar?

推荐答案

节点的

A node's pivot is a transformation matrix, the inverse of which is applied to the node before its transform property takes effect. For example, take a look at this bit from the default SceneKit Game template in Xcode:

let boxNode = SCNNode()
boxNode.geometry = SCNBox(width: 1, height: 1, length: 1, chamferRadius: 0.02)

如果设置boxNode的position，则该点对应于立方体的中心，并且如果旋转它(如模板在动画中所做的那样)，它将绕其中心旋转.

If you set the boxNode's position, that point corresponds to the center of the cube, and if you rotate it (as the template does in an animation), it spins around its center.

要更改锚点，请将pivot设置为平移变换:

To change the anchor point, set the pivot to a translation transform:

boxNode.pivot = SCNMatrix4MakeTranslation(0.5, 0.5, 0.5)

现在，当您设置position时，该点对应于多维数据集的右上前角，并且当您旋转多维数据集时，它围绕该角旋转.

Now, when you set the position that point corresponds to the top-right-front corner of the cube, and when you rotate the cube it spins around that corner.

更一般地，枢轴相对于节点自己的变换来变换节点的内容.假设您要模拟地球自转轴的进动.您可以通过创建两个动画来做到这一点:一个动画使pivot动画以使节点绕其自身的Y轴旋转，另一个动画给rotation动画以使该轴相对于包含该节点的空间移动.

More generally, a pivot transforms the contents of a node relative to the node's own transform. Suppose you wanted to model the precession of the Earth's axis of rotation. You could do this by creating two animations: one that animates pivot to spin the node around its own Y axis, and another that animates rotation to move that axis relative to the space containing the node.

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