同时使用Metal和SceneKit的问题

Question

I'm working on a little SceneKit project, and I want to generate my textures programmatically using a Metal Compute pipeline for speed. I have a basic pipeline set up that generates an MTLTexture and it works, but as soon as I add the SceneKit framework to the project, it fails claiming Function <X> was not found in the library . If I remove all references to SceneKit it works again.

I must be instantiating my library from the correct URL or it wouldn't work without SceneKit. What's blocking it? Is there a way around this issue, perhaps using an SCNRenderer?

[Edit] For more clarity, here's how I obtain a reference to my MTLLibrary:

    guard let url = Bundle.main.url(forResource: "MyLibrary", withExtension: "metallib") else {
        throw GeneratorError.metalLibraryNotFound
    }
    library = device.makeLibrary(URL: url)

A strong reference is kept by the calling object (along with the MTLDevice ), and it's a singleton so it remains in memory. To obtain the kernel function itself I then call the following function, which returns an appropriate pipeline state:

    guard let function = library.makeFunction(name: functionName) else {
        throw GeneratorError.functionNotFound(functionName)
    }
    return device.makeComputePipelineState(function: function)

Like I say, this works fine until SceneKit is added to the project - and simply adding the framework to the linked frameworks list is enough, I don't have to do anything with it - whereupon it simply can't find any of my functions.

Answer 1

I have found out what was causing this issue, but I am still highly confused as to why, so I'd appreciate any further input people have!

Essentially, I had split my Metal library up amongst several files to make it easier to work on. One had CIFilter-supported functions in, the other had Metal pipeline kernels. Now, I knew that the two were incompatible when both were linked in the main .metal file, so I'd commented one out temporarily but kept it for reference. I also had the linker flag -cikernel in build settings.

I'd suspected that the linker flag might cause problems, but removing it made things worse. Eventually I tried removing the linker flag AND the entire file that I had previously merely commented out. This worked! I guess the compiler must compile ALL .metal files regardless of their inclusion in the main file, and somehow, having CIFilter kernels and texturing kernels in the same library is a big no-no, even though they were not in the same namespace.

If anyone knows the reasoning behind this, I'd love to know! In the meantime I am simply going to remove all CIFilters and work with pure Metal-based compute pipelines instead.