使用 Swift 在 ARKit 中显示白色图像材料

Question

I have created node with SCNGeometryElement and apply image content material to display white and apply color content is working fine. I have attached code.

func getsquareDrawnLineFrom(pos1: SCNVector3,
                            pos2: SCNVector3,
                            pos3: SCNVector3) -> SCNNode {

    let square = SquareplanlineFrom(vector1: pos1, vector2: pos2, vector3: pos3)
    let material = SCNMaterial()
    // material.diffuse.contents = UIColor.red
    material.diffuse.contents = UIImage(named: "grid")
    square.materials = [material]
    let square1 = SCNNode(geometry: square)
    square1.name = "tringle"
    return square1
}

// get line geometry between three vectors
func SquareplanlineFrom(vector1: SCNVector3,
                        vector2: SCNVector3, 
                        vector3: SCNVector3) -> SCNGeometry {

    let indices: [Int32] = [0, 1, 2]
    let source = SCNGeometrySource(vertices: [vector1, vector2, vector3])
    let element = SCNGeometryElement(indices: indices, primitiveType: .triangles)

    return SCNGeometry(sources: [source], elements: [element])
}

Answer 1

For placing a texture on your custom geometry triangle you need implement two more important type properties:

SCNGeometrySource.Semantic.texcoord
SCNGeometrySource.Semantic.normal

which let a texture find out what are UV-coordinates and Poly normal direction, so texture can occupy a definite space on a poly surface.

Look at this post and this post at a GitHub to get an idea how to implement it .

Although, when you use regular SceneKit primitives (such as SCNSphere, SCNBox, SCNPlane, etc) or imported 3D models (in DAE, OBJ or USDZ file formats) you don't think about implementation of these type properties because the aforementioned geometry already contain them.