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DX11 Having support for DX9 , DX10 , DX11

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Hello. I want my game to support different software and hardware platforms automatically. Example of what I want to do: * User has Windows7 - DX11 Device will be created , if user has old hardware , the device will be created with the appropriate feature level. * User has Windows Vista - If user has a DX10 compatible hardware a DX10 device will be created , if the user has only DX9 compatible hardware than a DX9 device will be created. * User has Windows XP - Only a DX9 device will be created. My question is how I determine this? How do I determine using C++ the windows ( Or the Directx version installed ) the user is running and the hardware type so I can make this selection on the application start.

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Try to create the DX11 device, and if it doesn't work, jump down one level. DX11 is available on Vista too if you get the latest updates from Windows Update (SP2 and platform update).
The problem is that if you link to D3D11 in your app, it will fail to start if the D3D11 DLLs aren't available on the system. So to get the same app running on different systems like that, you need to dynamically load D3D11.dll etc. with the LoadLibrary Function.

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Quote:
Original post by Erik Rufelt
Try to create the DX11 device, and if it doesn't work, jump down one level. DX11 is available on Vista too if you get the latest updates from Windows Update (SP2 and platform update).
The problem is that if you link to D3D11 in your app, it will fail to start if the D3D11 DLLs aren't available on the system. So to get the same app running on different systems like that, you need to dynamically load D3D11.dll etc. with the LoadLibrary Function.


Ok that sounds simple enough. But what about people with Windows XP? Isn't XP missing a core component (WDDM) so even loading DX11 DLL's wont help , or would it?

Thank's for the fast reply :>

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What I mean is, D3D11.dll isn't available on XP, so LoadLibrary will return an error. Which is OK, you just handle that in your app. If you add D3D11.lib in your project link dependencies however, your app will fail to start with an error box. So you need to load it dynamically, and if it fails, you load D3D10.dll or D3D9.dll instead. (For D3D10/11 you might need to load DXGI.dll also, if you want to use those functions).
Once you have a library handle, you use the GetProcAddress Function, to get a function in that library. For example if you want the D3D11CreateDevice function, you use GetProcAddress(hD3D11Lib, "D3D11CreateDevice"). That will give you the function pointer, and you use that to create your D3D11 device. After that the usage of the ID3D11Device object is the same as before.
You also have to check the return code from the function of course, since someone could put the D3D11.dll DLL on their XP system, but the D3D11CreateDevice function would fail in that case.

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Quote:
Original post by Erik RufeltIf you add D3D11.lib in your project link dependencies however, your app will fail to start with an error box. So you need to load it dynamically, and if it fails, you load D3D10.dll or D3D9.dll instead.

This is not entirely true. Linking D3D11.lib technically has no bearing on what happens at runtime. It's statically linked to your program at compile time. If you also set a project setting to delay-load the appropriate DLLs (in this case, D3D11.dll and friends), the DLLs won't be loaded until they are called at runtime. You don't even need to use LoadLibrary.

In addition, D3D11 supports hardware all the way down to D3D9 level hardware, so as long as the appropriate drivers are installed you only have to write one version of your code that targets D3D11 and avoids using newer features if you're running on older hardware and you can avoid integrating at least D3D10.

D3D11 is still only supported on Vista and Win7 though, so you may still want a D3D9 renderer if XP support is crucial.

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There is no reason to support dx10. It is obsolete as of dx11 and dx11 feature levels since its supported by vista and 7. The real issue you will face is whether you will support the different features such as tesselation, geometry shaders, and compute shaders. None of these are supported in dx9 if you aren't using any of these features there is no reason to use anything other than dx9. If you are you will have a lot of issue with needing many different sets of shaders and software implementations of features not supported.

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Thank's everyone. Basically I figured out what to do. I found a function (http://msdn.microsoft.com/en-us/library/ms724451%28VS.85%29.aspx) to help me figure out what windows the machine is running. If it's XP , I initiate the DX9 Renderer , if it's Vista or 7 I initiate a DX11 Device with an appropriate feature level.

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Quote:
Original post by Mike.Popoloski
Quote:
Original post by Erik RufeltIf you add D3D11.lib in your project link dependencies however, your app will fail to start with an error box. So you need to load it dynamically, and if it fails, you load D3D10.dll or D3D9.dll instead.

This is not entirely true. Linking D3D11.lib technically has no bearing on what happens at runtime. It's statically linked to your program at compile time. If you also set a project setting to delay-load the appropriate DLLs (in this case, D3D11.dll and friends), the DLLs won't be loaded until they are called at runtime. You don't even need to use LoadLibrary.


How does this work if the appropriate DLLs aren't available, and the program should still run?
I have very limited experience with this so perhaps I just don't understand the process, but how would I write the following for example without LoadLibrary:

#include <DXGI.h>
#include <cstdio>

typedef HRESULT (WINAPI * LPCREATEDXGIFACTORY1)(REFIID, void**);

int main() {
HMODULE hDXGI = LoadLibrary(TEXT("dxgi.dll"));
if(hDXGI == NULL) {
DWORD dwErr = GetLastError();
printf("Failed to load dxgi.dll: %u\n", dwErr);
}
else {
LPCREATEDXGIFACTORY1 pCreateDXGIFactory1 = (LPCREATEDXGIFACTORY1)GetProcAddress(hDXGI, "CreateDXGIFactory1");
if(pCreateDXGIFactory1 == NULL) {
DWORD dwErr = GetLastError();
printf("Failed to get the CreateDXGIFactory1 function: %u\n", dwErr);
}
else {
IDXGIFactory1 *pFactory;

HRESULT hResult = pCreateDXGIFactory1(__uuidof(IDXGIFactory1), (void**)&pFactory);
if(FAILED(hResult)) {
printf("CreateDXGIFactory1 failed: 0x%08x\n", hResult);
}
else {
// Use pFactory
printf("IDXGIFactory1 created!\n");

pFactory->Release();
}
}

FreeLibrary(hDXGI);
}

return 0;
}

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You use a function like the one referenced above to determine which version of Windows you are running, and if you're on a non-supported system simply be sure to not call any D3D11 functions. As long as you never call a function from the DLL, it won't try to be loaded by the OS.

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I see. It doesn't work if the system could potentially have support though, as with D3D11. DXGI.dll in this case may or may not also be version 1.1.

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Note that while DX11 is available for Vista, it won't necessarily exist on all Vista machine. It'd be a good idea to detect this and recommend to the user to install the update.

As for DX9/DX11, I think that it's best to use just one API. Using both DX9 and DX11 will complicate your program's design and implementation considerably. Which one to use will depend on the target audience, but I think that for a game that's being started at this point in time, using DX11 is reasonable for a non-casual game, and making DX10 hardware the base requirement is also possible. The Steam Hardware Survey shows that 70% of users have DX10 hardware, and almost 50% have Vista/Win7. If you're doing an advanced game, it will take quite a bit of time to develop, and by then the majority of gamers are likely to have DX10 capable systems, IMO.

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As pointed out, you'd ship with, and install either the D3D11 or D3D9 runtimes based on which version of windows is present, so no error handling of delayload is technically required, but it's probably good practice to handle the error cases properly.

We use the delayload technique for XInput (since not everyone has a 360 controller... it's true!) If you attempt to use the DLL, and it cannot be loaded, an exception is thrown, at which point you can stop trying to use that library.

bool InitXInputAndCheckIfXInputAvailable()
{
__try
{
XInputEnable(true);
}
__except (EXCEPTION_EXECUTE_HANDLER)
{
return false;
}
return true;
}

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ET3D : Yes you are quiet right , some Vista users might still not have the DX11 update , I should definitely address that. About using multiple API's , it's a decision I made a while back because I want to share the game with friends and family , and most of them still only have XP , while a few got Vista and some got W7 ( Including myself ). So I started programming my game with support for several renderers in mind. I currently have a DX11 renderer and happily my design is abstracted enough so I can easily add a DX9 renderer with not much effort.

Namethatnobodyelsetook : Well handling errors is always a good practice , and this case is not an exception to the rule :)

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      m_pPSO->CreateShaderResourceBinding(&m_pSRB); Note that an SRB is only compatible with the pipeline state it was created from. SRB object inherits all static bindings from shaders in the pipeline, but is not allowed to change them.
      Mutable resources can only be set once for every instance of a shader resource binding. Such resources are intended to define specific material properties. For instance, a diffuse texture for a specific material is not expected to change once the material is defined and can be set right after the SRB object has been created:
      m_pSRB->GetVariable(SHADER_TYPE_PIXEL, "tex2DDiffuse")->Set(pDiffuseTexSRV); In some cases it is necessary to bind a new resource to a variable every time a draw command is invoked. Such variables should be labeled as dynamic, which will allow setting them multiple times through the same SRB object:
      m_pSRB->GetVariable(SHADER_TYPE_VERTEX, "cbRandomAttribs")->Set(pRandomAttrsCB); Under the hood, the engine pre-allocates descriptor tables for static and mutable resources when an SRB objcet is created. Space for dynamic resources is dynamically allocated at run time. Static and mutable resources are thus more efficient and should be used whenever possible.
      As you can see, Diligent Engine does not expose low-level details of how resources are bound to shader variables. One reason for this is that these details are very different for various APIs. The other reason is that using low-level binding methods is extremely error-prone: it is very easy to forget to bind some resource, or bind incorrect resource such as bind a buffer to the variable that is in fact a texture, especially during shader development when everything changes fast. Diligent Engine instead relies on shader reflection system to automatically query the list of all shader variables. Grouping variables based on three types mentioned above allows the engine to create optimized layout and take heavy lifting of matching resources to API-specific resource location, register or descriptor in the table.
      This post gives more details about the resource binding model in Diligent Engine.
      Setting the Pipeline State and Committing Shader Resources
      Before any draw or compute command can be invoked, the pipeline state needs to be bound to the context:
      m_pContext->SetPipelineState(m_pPSO); Under the hood, the engine sets the internal PSO object in the command list or calls all the required native API functions to properly configure all pipeline stages.
      The next step is to bind all required shader resources to the GPU pipeline, which is accomplished by IDeviceContext::CommitShaderResources() method:
      m_pContext->CommitShaderResources(m_pSRB, COMMIT_SHADER_RESOURCES_FLAG_TRANSITION_RESOURCES); The method takes a pointer to the shader resource binding object and makes all resources the object holds available for the shaders. In the case of D3D12, this only requires setting appropriate descriptor tables in the command list. For older APIs, this typically requires setting all resources individually.
      Next-generation APIs require the application to track the state of every resource and explicitly inform the system about all state transitions. For instance, if a texture was used as render target before, while the next draw command is going to use it as shader resource, a transition barrier needs to be executed. Diligent Engine does the heavy lifting of state tracking.  When CommitShaderResources() method is called with COMMIT_SHADER_RESOURCES_FLAG_TRANSITION_RESOURCES flag, the engine commits and transitions resources to correct states at the same time. Note that transitioning resources does introduce some overhead. The engine tracks state of every resource and it will not issue the barrier if the state is already correct. But checking resource state is an overhead that can sometimes be avoided. The engine provides IDeviceContext::TransitionShaderResources() method that only transitions resources:
      m_pContext->TransitionShaderResources(m_pPSO, m_pSRB); In some scenarios it is more efficient to transition resources once and then only commit them.
      Invoking Draw Command
      The final step is to set states that are not part of the PSO, such as render targets, vertex and index buffers. Diligent Engine uses Direct3D11-syle API that is translated to other native API calls under the hood:
      ITextureView *pRTVs[] = {m_pRTV}; m_pContext->SetRenderTargets(_countof( pRTVs ), pRTVs, m_pDSV); // Clear render target and depth buffer const float zero[4] = {0, 0, 0, 0}; m_pContext->ClearRenderTarget(nullptr, zero); m_pContext->ClearDepthStencil(nullptr, CLEAR_DEPTH_FLAG, 1.f); // Set vertex and index buffers IBuffer *buffer[] = {m_pVertexBuffer}; Uint32 offsets[] = {0}; Uint32 strides[] = {sizeof(MyVertex)}; m_pContext->SetVertexBuffers(0, 1, buffer, strides, offsets, SET_VERTEX_BUFFERS_FLAG_RESET); m_pContext->SetIndexBuffer(m_pIndexBuffer, 0); Different native APIs use various set of function to execute draw commands depending on command details (if the command is indexed, instanced or both, what offsets in the source buffers are used etc.). For instance, there are 5 draw commands in Direct3D11 and more than 9 commands in OpenGL with something like glDrawElementsInstancedBaseVertexBaseInstance not uncommon. Diligent Engine hides all details with single IDeviceContext::Draw() method that takes takes DrawAttribs structure as an argument. The structure members define all attributes required to perform the command (primitive topology, number of vertices or indices, if draw call is indexed or not, if draw call is instanced or not, if draw call is indirect or not, etc.). For example:
      DrawAttribs attrs; attrs.IsIndexed = true; attrs.IndexType = VT_UINT16; attrs.NumIndices = 36; attrs.Topology = PRIMITIVE_TOPOLOGY_TRIANGLE_LIST; pContext->Draw(attrs); For compute commands, there is IDeviceContext::DispatchCompute() method that takes DispatchComputeAttribs structure that defines compute grid dimension.
      Source Code
      Full engine source code is available on GitHub and is free to use. The repository contains tutorials, sample applications, asteroids performance benchmark and an example Unity project that uses Diligent Engine in native plugin.
      Atmospheric scattering sample demonstrates how Diligent Engine can be used to implement various rendering tasks: loading textures from files, using complex shaders, rendering to multiple render targets, using compute shaders and unordered access views, etc.

      Asteroids performance benchmark is based on this demo developed by Intel. It renders 50,000 unique textured asteroids and allows comparing performance of Direct3D11 and Direct3D12 implementations. Every asteroid is a combination of one of 1000 unique meshes and one of 10 unique textures.

      Finally, there is an example project that shows how Diligent Engine can be integrated with Unity.

      Future Work
      The engine is under active development. It currently supports Windows desktop, Universal Windows, Linux, Android, MacOS, and iOS platforms. Direct3D11, Direct3D12, OpenGL/GLES backends are now feature complete. Vulkan backend is coming next, and Metal backend is in the plan.
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