如何在Xamarin.iOS中将IMTLTexture赋值给SCNMaterialProperty的Contents？

I get exactly where you're stuck here—Swift handles the bridging between Metal textures and SceneKit's material properties seamlessly, but Xamarin's C# type system requires a bit more explicit handling for this conversion. Here are two reliable ways to fix that invalid cast error:

1. Cast the IMTLTexture to its concrete implementation #

The CreateTexture method returns an IMTLTexture interface, but the underlying object is actually a MTLTexture (which inherits directly from NSObject). You can safely cast it to the concrete type first:

// Your existing texture creation
IMTLTexture texture = device.CreateTexture(textureDescriptor);
// Cast to the concrete MTLTexture class
MTLTexture metalTexture = (MTLTexture)texture;

// Assign to the material property
if (node.Geometry?.FirstMaterial == null)
{
    // Make sure the material exists before accessing it
    node.Geometry.FirstMaterial = new SCNMaterial();
}
node.Geometry.FirstMaterial.Diffuse.Contents = metalTexture;

2. Use double casting to NSObject #

If you prefer to work with the IMTLTexture interface directly, you can first cast it to object (to unbox the underlying Objective-C instance) and then to NSObject:

// Your existing code
IMTLTexture texture = device.CreateTexture(textureDescriptor);
SCNNode node = new SCNNode();
// Assign geometry, etc.

// Safe conversion via object intermediate
if (node.Geometry?.FirstMaterial != null)
{
    node.Geometry.FirstMaterial.Diffuse.Contents = (NSObject)(object)texture;
}

Why this works #

In Swift, the compiler automatically bridges Objective-C types like MTLTexture to the appropriate Swift types and handles the assignment to SCNMaterialProperty.Contents without extra work. In Xamarin, since IMTLTexture is a C# interface wrapping the Objective-C class, you need to explicitly access the underlying NSObject-compatible instance either by casting to the concrete MTLTexture class or using the double cast trick.

内容的提问来源于stack exchange，提问作者michasaurus