如何将 mtl 纹理文件应用于 OBJ

Question

我正在使用ModelI/O来显示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，会显示 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])

应将 URL 传递到纹理文件，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)

附言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

您也可以尝试使用此方法。如果我没记错的话，它将连接 .mtl 文件和其他纹理。(如果写入 .obj 文件的 .mtl 文件的路径有效，并且 .mtl 中纹理的路径也有效(