SceneKit

Question

我想用 ARKit 使用自定义多边形平铺地面，自定义多边形由用户使用水平平面上的选定位置创建，但是平铺被拉伸并且无法正确显示，也许问题出在纹理坐标上，这段代码有什么问题？

let vertices: [SCNVector3] = ... //Selected positions by user        
var indices: [Int32] = [Int32(vertices.count)]
var index: Int32 = 0

for _ in vertices {
    indices.append(index)
    index += 1
}
    
let textureCoordinates = [  CGPoint(x: 0, y: 0),
                            CGPoint(x: 1, y: 0),
                            CGPoint(x: 0, y: 1),
                            CGPoint(x: 1, y: 1)
                         ]
    
let vertexSource = SCNGeometrySource(vertices: vertices)
let uvSource = SCNGeometrySource(textureCoordinates: textureCoordinates)
let indexData = Data(bytes: indices, 
                     count: indices.count * MemoryLayout<Int32>.size)
let element = SCNGeometryElement(data: indexData, 
                        primitiveType: .polygon, 
                       primitiveCount: 1, 
                        bytesPerIndex: MemoryLayout<Int32>.size)
let geometry = SCNPlane(sources: [vertexSource, uvSource], 
                       elements: [element]) //Creating geometry
   
//Tile material creation
let material = SCNMaterial()
material.isDoubleSided = true
material.diffuse.wrapS = .repeat
material.diffuse.wrapT = .repeat

//Tile image to tile polygon
material.diffuse.contents = UIImage(named: "tile")!
material.diffuse.contentsTransform = SCNMatrix4MakeScale(32, 32, 0)

geometry.firstMaterial = material

//Tiled Plan to put on the ground
let plane = SCNNode(geometry: geometry)
//Add custom polygon to sceneView
sceneView.scene.rootNode.addChildNode(plane)

编辑：

感谢 Andy，我更改了 contentsTransform，在变换比例上做了一些小改动，但仍然有同样的问题：

.init(
 m11: 5, m12: 0,    m13: 0,   m14: 0,
 m21: 0,    m22: 5, m23: 0,   m24: 0,
 m31: 0,    m32: 0,    m33: 1,   m34: 0,
 m41: 0.5,  m42: 0,    m43: 0,   m44: 1)

我的期望：

会发生什么：

Answer 1

纹理拉伸 由于 UV 贴图上的错误纹理映射而发生。您必须使用 m41（翻译 X）和 m42（翻译 Y）元素，它们包含在 SCNMatrix4 的第四列中。这就是当矩阵元素 m41 等于零时拉伸的样子：

material.diffuse.contentsTransform = .init(
                                       m11: 0.04, m12: 0,    m13: 0,   m14: 0,
                                       m21: 0,    m22: 0.04, m23: 0,   m24: 0,
                                       m31: 0,    m32: 0,    m33: 1,   m34: 0,
                                       m41: 0,    m42: 0,    m43: 0,   m44: 1)

偏移纹理

当您沿 X 轴移动纹理时，一切都改变了：

material.diffuse.contentsTransform = .init(
                                       m11: 0.04, m12: 0,    m13: 0,   m14: 0,
                                       m21: 0,    m22: 0.04, m23: 0,   m24: 0,
                                       m31: 0,    m32: 0,    m33: 1,   m34: 0,
                                       m41: 0.5,  m42: 0,    m43: 0,   m44: 1)

SceneKit – 自定义几何体上的拉伸纹理

SceneKit – Stretched texture on a Custom Geometry

swift

augmented-reality

arkit

偏移纹理