Is vulkan backend support mutiple bindless descriptor set?

[HuazyYang]

I use two different dynamic decriptor tables to arrange scene resources(textures/buffers) and render pass associated resources. HLSL resource binding profile are as following:

// Scene Bindless Resources
VK_BINDING(0, 1) ByteAddressBuffer SceneBuffers[] : register(t0, space1);
VK_BINDING(1, 1) Texture2D SceneTex2D[] : register(t0, space2);

// Fixed Bindless Resources
// ---------------------------------------------------------------------------------------
VK_BINDING(0, 2) Texture2D<float4> FixedTex2D[]: register(t0, space3);
VK_BINDING(1, 2) Texture2DArray<float4> FixedTex2DArray[]: register(t0, space4);
VK_BINDING(2, 2) RWTexture2D<float4> FixedRWTex2D[]: register(u0, space1);
VK_BINDING(3, 2) RWTexture2DArray<float4> FixedRWTex2DArray[]: register(u0, space2);

In C++ program side, two bindless layouts are created as following;

    nvrhi::BindlessLayoutDesc bindlessLayoutDesc;
    bindlessLayoutDesc.visibility = nvrhi::ShaderType::All;
    bindlessLayoutDesc.firstSlot = 0;
    bindlessLayoutDesc.maxCapacity = 1024;
    bindlessLayoutDesc.registerSpaces = {nvrhi::BindingLayoutItem::RawBuffer_SRV(1),
                                         nvrhi::BindingLayoutItem::Texture_SRV(2)};
    BindlessLayout = Device->createBindlessLayout(bindlessLayoutDesc);

    bindlessLayoutDesc.registerSpaces = {nvrhi::BindingLayoutItem::Texture_SRV(3),
                                         nvrhi::BindingLayoutItem::Texture_SRV(4),
                                         nvrhi::BindingLayoutItem::Texture_UAV(1),
                                         nvrhi::BindingLayoutItem::Texture_UAV(2)};
    FixedBindlessLayout = Device->createBindlessLayout(bindlessLayoutDesc);

and use two descriptor tables to map resource to bindless layout in rendering loop.

For D3D12 backend, it works fine, but vulkan backend does not. So my question is whether more than one descriptor table is allowed for vulkan backend?

[HuazyYang]

After look around vulkan descriptor layout and descriptor set document, I finally make it by adjusting vulkan binding set and binding point of vulkan RHI layer.

In HLSL source:

// Scene Bindless Resources
VK_BINDING(0, 1) ByteAddressBuffer SceneBuffers[] : register(t0, space1);
VK_BINDING(1, 1) Texture2D SceneTex2D[] : register(t0, space2);

// Fixed Bindless Resources
// ---------------------------------------------------------------------------------------
VK_BINDING(0, 2) Texture2D<float4> FixedTex2D[]: register(t0, space3);
VK_BINDING(0, 2) Texture2DArray<float4> FixedTex2DArray[]: register(t0, space4);
VK_BINDING(1, 2) RWTexture2D<float4> FixedRWTex2D[]: register(u0, space1);
VK_BINDING(1, 2) RWTexture2DArray<float4> FixedRWTex2DArray[]: register(u0, space2);

In C++ source:
Descriptor table construction:

    nvrhi::BindlessLayoutDesc bindlessLayoutDesc;
    bindlessLayoutDesc.visibility = nvrhi::ShaderType::All;
    bindlessLayoutDesc.firstSlot = 0;
    bindlessLayoutDesc.maxCapacity = 1024;
    bindlessLayoutDesc.registerSpaces = {nvrhi::BindingLayoutItem::RawBuffer_SRV(1),
                                         nvrhi::BindingLayoutItem::Texture_SRV(2)};
    BindlessLayout = Device->createBindlessLayout(bindlessLayoutDesc);

    if (Device->getGraphicsAPI() == nvrhi::GraphicsAPI::D3D12) {
        bindlessLayoutDesc.registerSpaces = {nvrhi::BindingLayoutItem::Texture_SRV(3),
                                             nvrhi::BindingLayoutItem::Texture_SRV(4),
                                             nvrhi::BindingLayoutItem::Texture_UAV(1),
                                             nvrhi::BindingLayoutItem::Texture_UAV(2)};
    } else {
        bindlessLayoutDesc.registerSpaces = {nvrhi::BindingLayoutItem::Texture_SRV(0),
                                             nvrhi::BindingLayoutItem::Texture_UAV(1)};
    }
    FixedBindlessLayout = Device->createBindlessLayout(bindlessLayoutDesc);

Pipeline creation:

    psoDesc.bindingLayouts = { m_GlobalResources->BindingLayout, nullptr, m_GlobalResources->FixedBindlessLayout };

Descriptor set(heap) binding:

    psoDesc.bindingLayouts = { m_GlobalResources->BindingLayout, nullptr, m_GlobalResources->FixedBindlessLayout };

Note I use null as placeholder for descriptor layout and binding set. which is not necessary for D3D12, but increment binding set index for vulkan. In order to support this convention, I also modified some nvrhi-d3d12-compute source, but may subject to UB for other circumstances.