问题

I created an object (a face) in Blender, exported it as a .obj, then used RealityConverter to make it a .usdz file.

我在Blender中创建了一个对象（一个面孔），将其导出为.obj文件，然后使用RealityConverter将其制作成.usdz文件。

I imported the .usdz file into my Xcode project. This is how I've attempted to anchor the Blender object to the user's face:

我将.usdz文件导入到我的Xcode项目中。以下是我尝试将Blender对象锚定到用户脸部的方式：

let cat = try! Entity.loadAnchor(named: "alienCat")
uiView.scene.addAnchor(cat)

When I use the above code with a simple object I created in Reality Composer, it works as expected and is anchored perfectly on the user's face.

当我使用上述代码与我在Reality Composer中创建的简单对象一起使用时，它按预期工作，并完美地锚定在用户的脸上。

But when I try the same code with my custom made .usdz file from Blender, the object doesn't appear on screen.

但是，当我尝试使用相同的代码与我在Blender中制作的自定义.usdz文件一起使用时，对象不会显示在屏幕上。

As I rotate the phone though, I see a large, blown up version floating above. I've attached 2 screenshots:

1. The camera facing my face, and my face is black (expected). But no object attached to my face (unexpected).

但是，当我旋转手机时，我看到一个大的、放大的版本浮在上方。我附上了2张屏幕截图：

1. 面向我的脸的相机，我的脸是黑色的（预期的）。但没有对象附在我的脸上（意外的）。

2. When I rotate the phone, I see my object floating way above my head and MUCH bigger than expected:
   

3. 当我旋转手机时，我看到我的对象浮在我的头上远远高于预期，并且比预期的要大得多：

When I run the code, this is the error I get in the Xcode console:

当我运行代码时，在Xcode控制台中出现以下错误：

Warning: in AppendProperty at line 858 of sdf/path.cpp -- Can only append a property 'preliminary:anchoring:type' to a prim path (/)
Warning: in AppendProperty at line 858 of sdf/path.cpp -- Can only append a property 'triggers' to a prim path (/)

I believe my errors are originating from however I am creating my .obj in Blender. I'd like to fix these errors in Blender if possible. With the goal of just importing a .usdz and it works as expected. There was an answer posted here: https://stackoverflow.com/questions/65896647/realitykit-getting-runtime-warning-when-placing-a-model-in-arview by Andy Jazz. And he says If you setup a preliminary anchoring for USDZ model, then Xcode will not print such warnings.

我相信我的错误是由我在Blender中创建.obj文件的方式引起的。如果可能的话，我想在Blender中修复这些错误，目标是只需导入.usdz文件，它就能按预期工作。这里有一个答案：https://stackoverflow.com/questions/65896647/realitykit-getting-runtime-warning-when-placing-a-model-in-arview，作者是Andy Jazz。他说：“如果您为USDZ模型设置了初步锚定，那么Xcode就不会打印这样的警告。”

Is there a way to set up this preliminary anchoring in Blender?

在Blender中是否有一种方法来设置这个初步锚定？

How do I get these errors removed and have my .usdz object placed on the face as expected, and in an appropriate size?

如何消除这些错误，并使我的.usdz对象按预期放置在脸上，以及以适当的大小？

let cat = try! Entity.loadAnchor(named: "alienCat")
uiView.scene.addAnchor(cat)

Warning: in AppendProperty at line 858 of sdf/path.cpp -- Can only append a property 'preliminary:anchoring:type' to a prim path (/)
Warning: in AppendProperty at line 858 of sdf/path.cpp -- Can only append a property 'triggers' to a prim path (/)

答案1

得分: 0

缩放问题

从Blender或Maya导出时，模型的比例默认为100:1（因为您将模型以厘米比例导出，而不是RealityKit的米比例）。运行面部跟踪时，面具的枢轴点与面具表面之间的距离始终大于0，这意味着在100:1的比例下，这个距离增加了一百倍。枢轴点甚至可以位于模型的边界框之外。还要检查Blender模型的轴是朝上的：正Y还是正Z。

anchor.scale /= 100

anchor.scale /= 100