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      While working on a project using D3D12 I was getting an exception being thrown while trying to get a D3D12_CPU_DESCRIPTOR_HANDLE. The project is using plain C so it uses the COBJMACROS. The following application replicates the problem happening in the project.
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DX12 [Dx12] Need help with DescriptorHeap

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Hi, I was playing around with dx12 using sharpdx beta.

I'm able to render simple models now. However I went into troubles when trying to render models with several sub parts. The texture I uploaded is not displaying for second part.


This is how I do it:


1. Create a root signature

var rootSignatureDesc = new RootSignatureDescription(

                // Root Parameters
                    new RootParameter(ShaderVisibility.All,
                        new []
                            new DescriptorRange()
                                RangeType = DescriptorRangeType.ShaderResourceView,
                                DescriptorCount = 2,
                                OffsetInDescriptorsFromTableStart = -1,
                                BaseShaderRegister = 0
                            new DescriptorRange()
                                RangeType = DescriptorRangeType.ConstantBufferView,
                                DescriptorCount = 1,
                                OffsetInDescriptorsFromTableStart = -1,
                                BaseShaderRegister = 0
                    new RootParameter(ShaderVisibility.Pixel,
                        new DescriptorRange()
                            RangeType = DescriptorRangeType.Sampler,
                            DescriptorCount = 1,
                            OffsetInDescriptorsFromTableStart = -1,
                            BaseShaderRegister = 0

2. Create Descriptor Heap for srv and cbf

var srvCbvHeapDesc = new DescriptorHeapDescription()
                DescriptorCount = 3,
                Flags = DescriptorHeapFlags.ShaderVisible,
                Type = DescriptorHeapType.ConstantBufferViewShaderResourceViewUnorderedAccessView

            srvCbvHeap = device.CreateDescriptorHeap(srvCbvHeapDesc);

3.Upload textures

var tex = Texture.LoadFromFile("../../models/test.tga");
            byte[] textureData = tex.Data;
            TextureWidth = tex.Width; TextureHeight = tex.Height;

            var textureDesc = ResourceDescription.Texture2D(Format.B8G8R8A8_UNorm, TextureWidth, TextureHeight, 1, 1, 1, 0, ResourceFlags.None, TextureLayout.Unknown, 0);
            texture = device.CreateCommittedResource(new HeapProperties(HeapType.Upload), HeapFlags.None, textureDesc, ResourceStates.GenericRead, null);
            texture.Name = "Texture";

            var handle = GCHandle.Alloc(textureData, GCHandleType.Pinned);
            var ptr = Marshal.UnsafeAddrOfPinnedArrayElement(textureData, 0);
            texture.WriteToSubresource(0, null, ptr, TextureWidth * 4, textureData.Length);

4. Create Shader Resource View Description for each texture by offsetting the heap address

var Step = device.GetDescriptorHandleIncrementSize(DescriptorHeapType.ConstantBufferViewShaderResourceViewUnorderedAccessView);
device.CreateShaderResourceView(texture[i], srvDesc, srvCbvHeap.CPUDescriptorHandleForHeapStart + I * Step);

5.When building command list I set the descriptor table for each texture resource by offsetting

            DescriptorHeap[] descHeaps = new[] { srvCbvHeap, samplerViewHeap };
            commandList.SetDescriptorHeaps(descHeaps.GetLength(0), descHeaps);
            commandList.SetGraphicsRootDescriptorTable(0, srvCbvHeap.GPUDescriptorHandleForHeapStart);
            commandList.SetGraphicsRootDescriptorTable(1, samplerViewHeap.GPUDescriptorHandleForHeapStart);

draw first

commandList.SetGraphicsRootDescriptorTable(0, srvCbvHeap.GPUDescriptorHandleForHeapStart + Step * i);

draw second

But the thing is only the first part will have texture. I'm still trying to understand how the whole resource management works but it looks so complex. Please help, I checked the cpp sample code on GitHub but can't find what I did wrong.


Thanks in advance.

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Hi, I'm using SharpDx too.

Well, how I can see you are using 3 items (2 for textures and 1 constant buffer) in the same RootParameters


so, from any position in your heap, D3D expects this 3 items

For example

tex1,tex2,constant buffer.

If you set offset to 0 D3D will start loading resource from tex1 position.


But if you increase just by one you'll have it starting from tex2 and read like this

tex2,constant buffer,??? 

so you must pay attention. It doesn't seem right.



When you combine many resources in one RootParameter you must pay attention that items are in the right number and order.


I've published some demo in SharpDx on Github



and I've a website too (http://www.notjustcode.net) where I've started Direct3D12 tutorial using SharpDx. It's in italian but you can try to translate with bar I've added?

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