SceneKit - SCNText对心不正确

Question

我试图使文本字符串(SCNText)适合于下面代码中的一个框(SCNBox)。框的大小看起来是正确的，但文本不在框的右中心。有什么办法吗？谢谢

let geoText = SCNText(string: "Hello", extrusionDepth: 1.0)
geoText.font = UIFont (name: "Arial", size: 8)
geoText.firstMaterial!.diffuse.contents = UIColor.red
let textNode = SCNNode(geometry: geoText)

let (minVec, maxVec) = textNode.boundingBox
scnScene.rootNode.addChildNode(textNode)

let w = CGFloat(maxVec.x - minVec.x)
let h = CGFloat(maxVec.y - minVec.y)
let d = CGFloat(maxVec.z - minVec.z)

let geoBox = SCNBox(width: w, height: h, length: d, chamferRadius: 0)
geoBox.firstMaterial!.diffuse.contents = UIColor.green.withAlphaComponent(0.5)
scnScene.rootNode.addChildNode(boxNode)

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编辑：我添加了一个新的字符串映像(没有SCNBox节点)和debugOptions showBoundingBoxes来查看它的边界框

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解决方案1:

根据vdugnist的答案，我为任何想要测试的人创建了一个操场代码：

import UIKit
import SceneKit
import PlaygroundSupport

var sceneView = SCNView(frame: CGRect(x: 0, y: 0, width: 600, height: 600))
var scene = SCNScene()
sceneView.scene = scene
PlaygroundPage.current.liveView = sceneView

let geoText = SCNText(string: "Hello", extrusionDepth: 1.0)
geoText.font = UIFont (name: "Arial", size: 12)
geoText.firstMaterial!.diffuse.contents = UIColor.red
let textNode = SCNNode(geometry: geoText)

let (minVec, maxVec) = textNode.boundingBox
textNode.position = SCNVector3(x: (minVec.x - maxVec.x) / 2, y: minVec.y - maxVec.y, z: 0)
textNode.pivot = SCNMatrix4MakeTranslation((maxVec.x - minVec.x) / 2, 0, 0)
scene.rootNode.addChildNode(textNode)

let w = CGFloat(maxVec.x - minVec.x)
let h = CGFloat(maxVec.y - minVec.y)
let d = CGFloat(maxVec.z - minVec.z)

let geoBox = SCNBox(width: w, height: h, length: d, chamferRadius: 0)
geoBox.firstMaterial!.diffuse.contents =   UIColor.green.withAlphaComponent(0.5)
let boxNode = SCNNode(geometry: geoBox)
boxNode.position = SCNVector3Make((maxVec.x - minVec.x) / 2 + minVec.x, (maxVec.y - minVec.y) / 2 + minVec.y, 0);
textNode.addChildNode(boxNode)

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解决方案2:

我需要将文本移动到零位置(0，0，0)，而不是移动文本和周围框，因此我继续从解决方案1中更改文本的枢轴。

import UIKit
import SceneKit
import PlaygroundSupport


var sceneView = SCNView(frame: CGRect(x: 0, y: 0, width: 600, height: 600))
var scene = SCNScene()
sceneView.scene = scene
PlaygroundPage.current.liveView = sceneView


let geoText = SCNText(string: "Hello", extrusionDepth: 1.0)
geoText.font = UIFont (name: "Arial", size: 12)
geoText.firstMaterial!.diffuse.contents = UIColor.red
let textNode = SCNNode(geometry: geoText)

let (minVec, maxVec) = textNode.boundingBox
textNode.pivot = SCNMatrix4MakeTranslation((maxVec.x - minVec.x) / 2 + minVec.x, (maxVec.y - minVec.y) / 2 + minVec.y, 0)
scene.rootNode.addChildNode(textNode)

let w = CGFloat(maxVec.x - minVec.x)
let h = CGFloat(maxVec.y - minVec.y)
let d = CGFloat(maxVec.z - minVec.z)

let geoBox = SCNBox(width: w, height: h, length: d, chamferRadius: 0)
geoBox.firstMaterial!.diffuse.contents = UIColor.green.withAlphaComponent(0.6)
let boxNode = SCNNode(geometry: geoBox)
scene.rootNode.addChildNode(boxNode)

Answer 1

SCNText与其他几何学的不同之处在于SCNText原点位于左下角。在其他几何学中，它是底部的中心。

要修复父节点中的文本位置，可以将它的透视点x设置为宽度的一半：

SCNVector3 min, max;
[textNode getBoundingBoxMin:&min max:&max];
textNode.pivot = SCNMatrix4MakeTranslation((max.x - min.x) / 2, 0, 0);

要修复子节点的位置，您应该将它们的位置设置为宽度的一半加上分钟：

SCNVector3 min, max;
[textNode getBoundingBoxMin:&min max:&max];
subnode.position = SCNVector3Make((max.x - min.x) / 2 + min.x, (max.y - min.y) / 2 + min.y, 0);

Answer 2

Swift:正确的父节点中的中心文本节点

let (min, max) = textNode.boundingBox

let dx = min.x + 0.5 * (max.x - min.x)
let dy = min.y + 0.5 * (max.y - min.y)
let dz = min.z + 0.5 * (max.z - min.z)
textNode.pivot = SCNMatrix4MakeTranslation(dx, dy, dz)

let textNodeParent = SCNNode()
textNodeParent.addChildNode(textNode)

Answer 3

要找到包围框的中心，需要在除以2之前添加(而不是减去) min和max。

textNode.position = SCNVector3(x: (minVec.x + maxVec.x) / 2, y: minVec.y + maxVec.y, z: 0)