# DX11 Locking lowest mip levels of a DXT texture

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Hi, I'm writing a cross platform engine (GL, GL ES, DX9, DX10, DX11), I've got a Texture class with a Lock and Unlock method, in directX, depending on the pool & usage some textures can be locked directly and some cannot and must use a temporary "staging" texture ( or surface for locking a single mip level ), this works perfectly, except with DX9...

In (more or less) pseudo code this look like this (Considering only the particular case of a DXT texture in D3DPOOL_DEFAULT which cannot be locked directly):

Texture::Lock( u32 _mipLevel ){      u32 mipWidth, mipHeight;      GetMipMapDimensions( _mipLevel, mipWidth, mipHeight );      #ifdef TRY_FORCING_MINIMUM_STAGING_TEX_SIZE                 //DX9 complains about creating DXT textures less than 4x4 in size     	 mipWidth = Max( mipWidth, 4 );     	 mipHeight = Max( mipHeight, 4 );      #endif      pDevice->CreateTexture( mipWidth, mipHeight,                                            1,//mip maps 		           0,//usage		           format,	                           D3DPOOL_SYSTEMMEM,                                          &m_pStagingTexture,  NULL );      m_pStagingTexture->Lock( ... );}Texture::Unlock( u32 _mipLevel ){	if( m_pStagingTexture )	{		m_pStagingTexture->UnlockRect( 0 );		IDirect3DSurface9* pStagingSurface;		IDirect3DSurface9* pDestSurface;		m_pStagingTexture->GetSurfaceLevel( 0, &pStagingSurface );		((IDirect3DTexture9*)m_pTex)->GetSurfaceLevel( _mipLevel, &pDestSurface );		//Here I also tried to call UpdateSurface with various parameters for pSourceRect and pDestinationPoint instead of NULL, with no success :(		pDevice->UpdateSurface( pStagingSurface, NULL, pDestSurface, NULL ); 		SAFE_RELEASE( m_pStagingTexture )	}}

This works nicely for uncompressed formats, but this breaks when locking the lowest mip levels (1x1 and 2x2) because of the DXT 4x4 block size

if TRY_FORCING_MINIMUM_STAGING_TEX_SIZE is NOT defined I get "Direct3D9: (ERROR) :DXT Formats require width/height to be a multiple of 4. CreateTexture failed." while creating the staging texture

if TRY_FORCING_MINIMUM_STAGING_TEX_SIZE is defined I get "Direct3D9: (ERROR) :pRect doesn't fit inside the surface" while calling UpdateSurface

I think I could get away by creating a staging texture with the full mip chain instead of only the mip level I'm locking and then using UpdateTexture instead of UpdateSurface but this would be very sub-optimal as well as making my code kind-of ugly

Do you know a solution to this problem ? ( I could eventually use D3DPOOL_MANAGED textures and lock them directly, but I'd rather avoid that solution if possible )

Nobody ?

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What if you specify NULL for the rect and point in UpdateSurface?

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Dispatch(32, 24, 1)

I'm attempting to implement some basic post-processing in my "engine" and the HLSL part of the Compute Shader and such I think I've understood, however I'm at a loss at how to actually get/use it's output for rendering to the screen.
Assume I'm doing something to a UAV in my CS:
RWTexture2D<float4> InputOutputMap : register(u0); I want that texture to essentially "be" the backbuffer.

I'm pretty certain I'm doing something wrong when I create the views (what I think I'm doing is having the backbuffer be bound as render target aswell as UAV and then using it in my CS):

DXGI_SWAP_CHAIN_DESC scd; ZeroMemory(&scd, sizeof(DXGI_SWAP_CHAIN_DESC)); scd.BufferCount = 1; scd.BufferDesc.Format = DXGI_FORMAT_R8G8B8A8_UNORM; scd.BufferUsage = DXGI_USAGE_RENDER_TARGET_OUTPUT | DXGI_USAGE_SHADER_INPUT | DXGI_USAGE_UNORDERED_ACCESS; scd.OutputWindow = wndHandle; scd.SampleDesc.Count = 1; scd.Windowed = TRUE; HRESULT hr = D3D11CreateDeviceAndSwapChain(NULL, D3D_DRIVER_TYPE_HARDWARE, NULL, NULL, NULL, NULL, D3D11_SDK_VERSION, &scd, &gSwapChain, &gDevice, NULL, &gDeviceContext); // get the address of the back buffer ID3D11Texture2D* pBackBuffer = nullptr; gSwapChain->GetBuffer(0, __uuidof(ID3D11Texture2D), (LPVOID*)&pBackBuffer); // use the back buffer address to create the render target gDevice->CreateRenderTargetView(pBackBuffer, NULL, &gBackbufferRTV); // set the render target as the back buffer CreateDepthStencilBuffer(); gDeviceContext->OMSetRenderTargets(1, &gBackbufferRTV, depthStencilView); //UAV for compute shader D3D11_UNORDERED_ACCESS_VIEW_DESC uavd; ZeroMemory(&uavd, sizeof(uavd)); uavd.Format = DXGI_FORMAT_R8G8B8A8_UNORM; uavd.ViewDimension = D3D11_UAV_DIMENSION_TEXTURE2D; uavd.Texture2D.MipSlice = 1; gDevice->CreateUnorderedAccessView(pBackBuffer, &uavd, &gUAV); pBackBuffer->Release();
After I render the scene, I dispatch like this:
gDeviceContext->OMSetRenderTargets(0, NULL, NULL); m_vShaders["cs1"]->Bind(); gDeviceContext->CSSetUnorderedAccessViews(0, 1, &gUAV, 0); gDeviceContext->Dispatch(32, 24, 0); //hard coded ID3D11UnorderedAccessView* nullview = { nullptr }; gDeviceContext->CSSetUnorderedAccessViews(0, 1, &nullview, 0); gDeviceContext->OMSetRenderTargets(1, &gBackbufferRTV, depthStencilView); gSwapChain->Present(0, 0); Worth noting is the scene is rendered as usual, but I dont get any results from the CS (simple gaussian blur)
I'm sure it's something fairly basic I'm doing wrong, perhaps my understanding of render targets / views / what have you is just completely wrong and my approach just makes no sense.

If someone with more experience could point me in the right direction I would really appreciate it!

On a side note, I'd really like to learn more about this kind of stuff. I can really see the potential of the CS aswell as rendering to textures and using them for whatever in the engine so I would love it if you know some good resources I can read about this!

Thank you <3

P.S I excluded the .hlsl since I cant imagine that being the issue, but if you think you need it to help me just ask

P:P:S. As you can see this is my first post however I do have another account, but I can't log in with it because gamedev.net just keeps asking me to accept terms and then logs me out when I do over and over

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• By mellinoe
Hi all,
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