Dx12 Vertex Buffer issue

[Gavin-Williams]

I'm trying to upload some vertex data, and when I call Map (last block of code here) I get a 0x0 pointer,

        // initialize triangle vertex data
        Span<Vertex> vertexData =
        [
            new() { 
                Position = new Vector3(0.0f, 0.25f, 0.0f), 
                Color = new Vector4(1.0f, 0.0f, 0.0f, 1.0f) },
            new() { 
                Position = new Vector3(0.25f, -0.25f, 0.0f), 
                Color = new Vector4(0.0f, 1.0f, 0.0f, 1.0f) },
            new() { 
                Position = new Vector3(-0.25f, -0.25f, 0.0f), 
                Color = new Vector4(0.0f, 0.0f, 1.0f, 1.0f) }
        ];

        VertexCount = (uint)vertexData.Length;

        // create vertex buffer in committed resource
        // - a committed resource is a heap dedicated to a single resource
        uint sizeInBytes = (uint)(sizeof(Vertex) * vertexData.Length);

        ResourceDescription bufferDesc = ResourceDescription.Buffer(sizeInBytes);
        if (Gpu.Device.CreateCommittedResource(
            new HeapProperties(HeapType.Default),
            HeapFlags.None,
            bufferDesc,
            ResourceStates.CopyDest,
            null,
            out VertexBuffer).Failure)
            throw new Exception();

        // create upload buffer in committed resource
        if (Gpu.Device.CreateCommittedResource(
            new HeapProperties(HeapType.Upload),
            HeapFlags.None,
            bufferDesc,
            ResourceStates.GenericRead,
            null,
            out ID3D12Resource uploadBuffer).Failure)
            throw new Exception();

        // copy vertex data to mapped memory / upload buffer
        // mapping creates an address in the PCI bus that the CPU can write to that
        // will be copied to the GPU buffer.
        void* busAddress = null;
        uploadBuffer.Map(0, busAddress);    // busAddress is 0x0 after here
        fixed (Vertex* dataPtr = vertexData)
            NativeMemory.Copy(dataPtr, busAddress, (uint)sizeInBytes);
        uploadBuffer.Unmap(0);

[amerkoleci]

Hi,
You need to take address of the busAddress:
uploadBuffer.Map(0, &busAddress);

Otherwise use helper methods I've added

https://github.com/amerkoleci/Vortice.Windows/blob/main/src/Vortice.Direct3D12/ID3D12Resource.cs#L45

[Gavin-Williams]

Ah, I did wonder at one point if it was something like that. I so rarely work with native code, I'm just never able to consistently remember all the little things about it's usage. I see void* as argument, and so I give it a void* - that's just what makes sense to me.

Thank you.