ios - 如何将 mtl 纹理文件应用于 OBJ

Question

我正在使用 ModelI/O 来展示 3D 模型。这是我的代码：

// Load the .OBJ file
    guard let url = Bundle.main.url(forResource: "agera r", withExtension: "obj") else {
        fatalError("Failed to find model file.")
    }

    let asset = MDLAsset(url:url)
    guard let object = asset.object(at: 0) as? MDLMesh else {
        fatalError("Failed to get mesh from asset.")
    }

    // Create a material from the various textures
    let scatteringFunction = MDLScatteringFunction()
    let material = MDLMaterial(name: "baseMaterial", scatteringFunction: scatteringFunction)
    let textureFileName = "agera_r.mtl"
    material.setTextureProperties([.baseColor: textureFileName])

    // Apply the texture to every submesh of the asset
    for submesh in object.submeshes!  {
        if let submesh = submesh as? MDLSubmesh {
            submesh.material = material
        }
    }

    // Wrap the ModelIO object in a SceneKit object
    let node = SCNNode(mdlObject: object)
    let scene = SCNScene()
    scene.rootNode.addChildNode(node)

    // Set up the SceneView
    sceneView.autoenablesDefaultLighting = true
    sceneView.allowsCameraControl = true
    sceneView.scene = scene
    sceneView.backgroundColor = UIColor.black
}
extension MDLMaterial {
func setTextureProperties(_ textures: [MDLMaterialSemantic:String]) -> Void {
    for (key,value) in textures {
        guard let url = Bundle.main.url(forResource: value, withExtension: "") else {
            fatalError("Failed to find URL for resource \(value).")
        }
        let property = MDLMaterialProperty(name:value, semantic: key, url: url)
        self.setProperty(property)
    }
}

问题是当应用程序运行时，显示 3D 模型但 .mtl 纹理文件不适用于它。如何解决这个问题？谢谢大家。

Answer 1

这几行的主要问题：

let textureFileName = "agera_r.mtl"
material.setTextureProperties([.baseColor: textureFileName])

您应该将 URL 传递给纹理文件，而不是 .mtl 文件 URL。 这段代码对我来说很好用：

目标-C

MDLScatteringFunction *scatFunction = [MDLScatteringFunction new];
MDLMaterial *mdlMaterial = [[MDLMaterial alloc] initWithName:@"material" scatteringFunction:scatFunction];
MDLMaterialProperty *bcProperty = [[MDLMaterialProperty alloc] initWithName:@"BaseColor" semantic:MDLMaterialSemanticBaseColor URL:textureFileURL];
[mdlMaterial setProperty:bcProperty];
SCNMaterial *material = [SCNMaterial materialWithMDLMaterial:mdlMaterial];
node.geometry.firstMaterial = material;

SWIFT

let scatFunction = MDLScatteringFunction()
let material = MDLMaterial(name: "material", scatteringFunction: scatFunction)
material.setTextureProperties(textures: [.baseColor: "model/texture.png"])
mesh.submeshes?.forEach {
    if let submesh = $0 as? MDLSubmesh {
        submesh.material = material
    }
}

baseNode = SCNNode(mdlObject: mesh)

附：这是完成该任务的两种略有不同的方法。

更新：

let baseNode = SCNScene(named: "mesh.obj")!.rootNode

您也可以尝试使用这种方法。如果我没记错的话，它将连接 .mtl 文件和其他纹理。 （如果 .obj 文件中写入的 .mtl 文件的路径有效，并且 .mtl 中的纹理路径也有效）