ios - ios - Gamekit 的 GKOctree 未找到元素

Question

我正在尝试使用GKOctree来有效地检索 3D 空间中的对象。但是，以下代码似乎无法按预期工作：

import GameplayKit

let tree = GKOctree(boundingBox: GKBox(
  boxMin: vector_float3(x: -10, y: -10, z: -10),
  boxMax: vector_float3(x: 10, y: 10, z: 10)
), minimumCellSize: 0.1)

tree.add(NSObject(), at: vector_float3(x: 0, y: 0, z: 0))
tree.elements(at: vector_float3(x: 0, y: 0, z: 0)).count // 1, fine

tree.elements(in: GKBox(
  boxMin: vector_float3(x: -1, y: -1, z: -1),
  boxMax: vector_float3(x: 1, y: 1, z: 1)
)).count // 0, ??

tree.elements(in: GKBox(
  boxMin: vector_float3(x: 1, y: 1, z: 1),
  boxMax: vector_float3(x: -1, y: -1, z: -1)
)).count // 0, well I tried

Answer 1

我做了一些测试，似乎有一个错误GKOctree可以反转 z 轴的符号。

如果您像这样更改代码，它可以工作：

import GameplayKit

let tree = GKOctree(boundingBox: GKBox(
    boxMin: vector_float3(x: -10, y: -10, z: 10),  // <---- check this out
    boxMax: vector_float3(x: 10, y: 10, z: -10)    // <---- check this out
), minimumCellSize: 0.1)

tree.add(NSObject(), at: vector_float3(x: 0, y: 0, z: 0))
tree.elements(at: vector_float3(x: 0, y: 0, z: 0)).count // 1, fine

tree.elements(in: GKBox(
    boxMin: vector_float3(x: -1, y: -1, z: -1),
    boxMax: vector_float3(x: 1, y: 1, z: 1)
)).count // 1, works

tree.elements(in: GKBox(
    boxMin: vector_float3(x: 1, y: 1, z: 1),
    boxMax: vector_float3(x: -1, y: -1, z: -1)
)).count // 1, works indeed