SceneKit - 自定义几何图形不显示 [英] SceneKit – Custom geometry does not show up

问题描述

我应该看到 2 个黄色三角形，但什么也没看到.

I should see 2 yellow triangles, but I see nothing.

class Terrain {

    private class func createGeometry () -> SCNGeometry {

        let sources = [
            SCNGeometrySource(vertices:[
                SCNVector3(x: -1.0, y: -1.0, z:  0.0),
                SCNVector3(x: -1.0, y:  1.0, z:  0.0),
                SCNVector3(x:  1.0, y:  1.0, z:  0.0),
                SCNVector3(x:  1.0, y: -1.0, z:  0.0)], count:4),
            SCNGeometrySource(normals:[
                SCNVector3(x:  0.0, y:  0.0, z: -1.0),
                SCNVector3(x:  0.0, y:  0.0, z: -1.0),
                SCNVector3(x:  0.0, y:  0.0, z: -1.0),
                SCNVector3(x:  0.0, y:  0.0, z: -1.0)], count:4)
        ]

        let elements = [
            SCNGeometryElement(indices: [0, 2, 3, 0, 1, 2], primitiveType: .Triangles)
        ]

        let geo = SCNGeometry(sources:sources, elements:elements)

        let mat = SCNMaterial()
        mat.diffuse.contents = UIColor.yellowColor()
        mat.doubleSided = true
        geo.materials = [mat]

        return geo
    }

    class func createNode () -> SCNNode {

        let node = SCNNode(geometry: createGeometry())
        node.name = "Terrain"
        node.position = SCNVector3()
        return node
    }
}

我是这样使用的:

let terrain = Terrain.createNode()
sceneView.scene?.rootNode.addChildNode(terrain)


let camera = SCNCamera()
camera.zFar = 10000
self.camera = SCNNode()
self.camera.camera = camera
self.camera.position = SCNVector3(x: -20, y: 15, z: 30)
let constraint = SCNLookAtConstraint(target: terrain)
constraint.gimbalLockEnabled = true
self.camera.constraints = [constraint]

sceneView.scene?.rootNode.addChildNode(self.camera)

我看到其他具有非自定义几何图形的节点.怎么了?

I get other nodes with non-custom geometry which I see. What's wrong?

推荐答案

注意:请参阅 Ash 的回答，对于现代 Swift 来说，这是一种比这更好的方法.

您的索引数组有错误的大小元素.它被推断为 [Int].你需要[CInt].

Your index array has the wrong size element. It's being inferred as [Int]. You need [CInt].

我将您的 elements 设置分解为:

I broke out your elements setup into:

    let indices = [0, 2, 3, 0, 1, 2] // [Int]
    print(sizeof(Int))               // 8
    print(sizeof(CInt))              // 4
    let elements = [
        SCNGeometryElement(indices: indices, primitiveType: .Triangles)
    ]

要像预期的 C 数组一样打包索引，请显式声明类型:

To get the indices to be packed like the expected C array, declare the type explicitly:

    let indices: [CInt] = [0, 2, 3, 0, 1, 2]

自定义 SceneKit 几何在 iOS 上的 Swift 中不起作用，但等效的 Objective C 代码确实更详细，但它是针对 Swift 1 编写的，因此您必须进行一些翻译.

Custom SceneKit Geometry in Swift on iOS not working but equivalent Objective C code does goes into more detail, but it's written against Swift 1, so you'll have to do some translation.

SCNGeometryElement(indices:,primitiveType:) 似乎没有记录在任何地方，尽管它确实出现在标题中.

SCNGeometryElement(indices:, primitiveType:) doesn't appear to be documented anywhere, although it does appear in the headers.

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