Sign in to follow this  
Anand Baumunk

DX11 (Order Independent) Transparency

Recommended Posts

Hello guys,

I started implementing transparency in my engine, and I got stuck on the usualy problem, I think, even thought I can't find very much helpful stuff on this.

I use a classic blendmode for transparent objects, and order them by the distance from the cam before drawing. This works fine if they are just a bunch of objects on behind another, but as soon as I rotate them or a model contains multiple polygons which have to been blended over oneanother, it becomes problematic.

For the rotationpart, I suppose I need a way to check the point of the object closest to the cam, and order them by this point rather than by just their position.

But I can't see someone preordering the triangles inside a mesh to get which transparent one needs to get drawn first.

As a solution, I have read about Order Independent Transparency, which is only for dx11, but that would be fine with me. I can't seem to pick up a good tutorial on this, so I may aswell ask you for one.

Or do you have another way of fixing those two problems?

 

Thanks so much!

-gnomgrol

Share this post


Link to post
Share on other sites

I had some help earlier on a similar issue, if you search for the topic "Rendering Intersecting Premultiplied Transparent Planes" and look at the Billboard example in the Microsoft XNA samples site they show how two passes can be used to prevent intersecting planes from creating weird depth effects.

Share this post


Link to post
Share on other sites

Additive blending is the only blending that can be drawn without drawing back to front, yes, for everything else I always implemented a simple binary tree that receives all the triangles being sent to the renderer, inserting them into the tree based on their distance, and then when its time to draw them to the screen I just walk the tree drawing from back to front, deconstructing the tree as the triangles are rendered. This entails building a new tree each frame, but it could be set up to only build a new tree once things have moved around enough to require a new tree being built. Also, for large triangles that could be intersecting eachother this won't work properly, but it works well enough for most cases. If you have a lot of triangles in your scene, its better to precompute something like a BSP tree for the static geometry, as it wouldn't be very efficient to rebuild a distance binary tree every frame (or even every couple of frames) for tens-of-thousands of triangles.

Share this post


Link to post
Share on other sites

Hi!

 

What you ended up using is called „alpha test“ and is not truly a solution to the blending of many transparent objects, though it is a common hack to avoid the problem.

Whenever you really need to approach true order-independent transparency, there are a number of methods:

  • Depth peeling [Everitt 01, Bavoil & Myers 08] (Requires to know the number of layers, but was used quite often in research papers. Also works on Dx9.)
  • Concurrent linked list construction [Yang et al. 10, Yakiimo 10]-> do not look into the DxSDK sample (OIT11). Last time I looked, it was poorly implemented (didn’t use shared memory at all).  Check the version of Yakiimo. He implemented it faster, even with multi-sampling. This technique grew more useful by the recent advances of the graphics hardware. Requires Dx11.
  • Stochastic transparency [Enderton et al. 10] (also rather a research thingy. It can handle an arbitrary number of layers, but consumes much performance to get it frame-to-frame coherent). Needs Dx 10.1 if I recall correctly, as it works on the coverage mask.
  • The list goes on... stencil routing etc... (Look into the related work of the papers I linked, if you want to learn more.)

AFAIK, true order-independent transparency was yet too expensive for games. (If someone knows a game that used OIT, please let me know!) It is easier to work around it or just sort the transparent objects by depth. (Of course, this doesn’t work in all cases, but you can tell your artist to circumvent the ugly cases.)
I’m creating technical demos and prototypes, so I can afford to use the concurrent linked list construction.

 

Best regards!
 

PS: Links don't seem to work at the moment, so I post the URLs.

Everitt 01: http://gamedevs.org/uploads/interactive-order-independent-transparency.pdf

Baviol & Myers 08: http://developer.download.nvidia.com/SDK/10/opengl/src/dual_depth_peeling/doc/DualDepthPeeling.pdf

Yang et al. 10: http://onlinelibrary.wiley.com/doi/10.1111/j.1467-8659.2010.01725.x/abstract

Yakiimo 10: http://www.yakiimo3d.com/2010/07/19/dx11-order-independent-transparency/

Enderton et al. 10: http://www.enderton.org/eric/pub/StochasticTransparency_I3D2010.pdf

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this  

  • Forum Statistics

    • Total Topics
      628293
    • Total Posts
      2981870
  • Similar Content

    • By GreenGodDiary
      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
    • By noodleBowl
      I was wondering if anyone could explain the depth buffer and the depth stencil state comparison function to me as I'm a little confused
      So I have set up a depth stencil state where the DepthFunc is set to D3D11_COMPARISON_LESS, but what am I actually comparing here? What is actually written to the buffer, the pixel that should show up in the front?
      I have these 2 quad faces, a Red Face and a Blue Face. The Blue Face is further away from the Viewer with a Z index value of -100.0f. Where the Red Face is close to the Viewer with a Z index value of 0.0f.
      When DepthFunc is set to D3D11_COMPARISON_LESS the Red Face shows up in front of the Blue Face like it should based on the Z index values. BUT if I change the DepthFunc to D3D11_COMPARISON_LESS_EQUAL the Blue Face shows in front of the Red Face. Which does not make sense to me, I would think that when the function is set to D3D11_COMPARISON_LESS_EQUAL the Red Face would still show up in front of the Blue Face as the Z index for the Red Face is still closer to the viewer
      Am I thinking of this comparison function all wrong?
      Vertex data just in case
      //Vertex date that make up the 2 faces Vertex verts[] = { //Red face Vertex(Vector4(0.0f, 0.0f, 0.0f), Color(1.0f, 0.0f, 0.0f)), Vertex(Vector4(100.0f, 100.0f, 0.0f), Color(1.0f, 0.0f, 0.0f)), Vertex(Vector4(100.0f, 0.0f, 0.0f), Color(1.0f, 0.0f, 0.0f)), Vertex(Vector4(0.0f, 0.0f, 0.0f), Color(1.0f, 0.0f, 0.0f)), Vertex(Vector4(0.0f, 100.0f, 0.0f), Color(1.0f, 0.0f, 0.0f)), Vertex(Vector4(100.0f, 100.0f, 0.0f), Color(1.0f, 0.0f, 0.0f)), //Blue face Vertex(Vector4(0.0f, 0.0f, -100.0f), Color(0.0f, 0.0f, 1.0f)), Vertex(Vector4(100.0f, 100.0f, -100.0f), Color(0.0f, 0.0f, 1.0f)), Vertex(Vector4(100.0f, 0.0f, -100.0f), Color(0.0f, 0.0f, 1.0f)), Vertex(Vector4(0.0f, 0.0f, -100.0f), Color(0.0f, 0.0f, 1.0f)), Vertex(Vector4(0.0f, 100.0f, -100.0f), Color(0.0f, 0.0f, 1.0f)), Vertex(Vector4(100.0f, 100.0f, -100.0f), Color(0.0f, 0.0f, 1.0f)), };  
    • By mellinoe
      Hi all,
      First time poster here, although I've been reading posts here for quite a while. This place has been invaluable for learning graphics programming -- thanks for a great resource!
      Right now, I'm working on a graphics abstraction layer for .NET which supports D3D11, Vulkan, and OpenGL at the moment. I have implemented most of my planned features already, and things are working well. Some remaining features that I am planning are Compute Shaders, and some flavor of read-write shader resources. At the moment, my shaders can just get simple read-only access to a uniform (or constant) buffer, a texture, or a sampler. Unfortunately, I'm having a tough time grasping the distinctions between all of the different kinds of read-write resources that are available. In D3D alone, there seem to be 5 or 6 different kinds of resources with similar but different characteristics. On top of that, I get the impression that some of them are more or less "obsoleted" by the newer kinds, and don't have much of a place in modern code. There seem to be a few pivots:
      The data source/destination (buffer or texture) Read-write or read-only Structured or unstructured (?) Ordered vs unordered (?) These are just my observations based on a lot of MSDN and OpenGL doc reading. For my library, I'm not interested in exposing every possibility to the user -- just trying to find a good "middle-ground" that can be represented cleanly across API's which is good enough for common scenarios.
      Can anyone give a sort of "overview" of the different options, and perhaps compare/contrast the concepts between Direct3D, OpenGL, and Vulkan? I'd also be very interested in hearing how other folks have abstracted these concepts in their libraries.
    • By turanszkij
      If I do a buffer update with MAP_NO_OVERWRITE or MAP_DISCARD, can I just write to the buffer after I called Unmap() on the buffer? It seems to work fine for me (Nvidia driver), but is it actually legal to do so? I have a graphics device wrapper and I don't want to expose Map/Unmap, but just have a function like void* AllocateFromRingBuffer(GPUBuffer* buffer, uint size, uint& offset); This function would just call Map on the buffer, then Unmap immediately and then return the address of the buffer. It usually does a MAP_NO_OVERWRITE, but sometimes it is a WRITE_DISCARD (when the buffer wraps around). Previously I have been using it so that the function expected the data upfront and would copy to the buffer between Map/Unmap, but now I want to extend functionality of it so that it would just return an address to write to.
    • By mister345
      Trying to write a multitexturing shader in DirectX11 - 3 textures work fine, but adding 4th gets sampled as black!
      Could you please look at the textureClass.cpp line 79? - I'm guess its D3D11_TEXTURE2D_DESC settings are wrong, 
      but no idea how to set it up right. I tried changing ArraySize from 1 to 4, but does nothing. If thats not the issue, please look
      at the LightShader_ps - maybe doing something wrong there? Otherwise, no idea.
          // Setup the description of the texture.
          textureDesc.Height = height;
          textureDesc.Width = width;
          textureDesc.MipLevels = 0;
          textureDesc.ArraySize = 1;
          textureDesc.Format = DXGI_FORMAT_R8G8B8A8_UNORM;
          textureDesc.SampleDesc.Count = 1;
          textureDesc.SampleDesc.Quality = 0;
          textureDesc.Usage = D3D11_USAGE_DEFAULT;
          textureDesc.BindFlags = D3D11_BIND_SHADER_RESOURCE | D3D11_BIND_RENDER_TARGET;
          textureDesc.CPUAccessFlags = 0;
          textureDesc.MiscFlags = D3D11_RESOURCE_MISC_GENERATE_MIPS;
      Please help, thanks.
      https://github.com/mister51213/DirectX11Engine/blob/master/DirectX11Engine/Texture.cpp
       
  • Popular Now