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OpenGL OpenGL and Windows Vista

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On some forums i've been suggested to switch to DirectX since Windows Vista will have a very poor support for Opengl API's. I recall also seeing a sort of "petition" against MS regarding this subject at opengl.org, but unfortunately i couldn't understand all of that document (english is not my first language). I really hope it won't be like that, i love OpenGL and i don't want to start to study another graphics programming API. No words to say that if all this is true, well it seems very unfair to me.

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Original post by Alessandro
On some forums i've been suggested to switch to DirectX since Windows Vista will have a very poor support for Opengl API's.
I recall also seeing a sort of "petition" against MS regarding this subject at opengl.org, but unfortunately i couldn't understand all of that document (english is not my first language).
I really hope it won't be like that, i love OpenGL and i don't want to start to study another graphics programming API. No words to say that if all this is true, well it seems very unfair to me.


an alternative would be suse 10 + nvidia drivers *they got an installer for suse* :)

I will try this out in 2 months when my exams are over

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Microsoft is doing, with Vista, what they did with XP. On XP, Microsoft only provided version 1.1 of OpenGL, and third party companies were left to provide additional versions and support. With Vista, Microsoft made the decision to provide support up until 1.4. And, again, other people would have to give the additional support.

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Original post by Dorvo
Microsoft is doing, with Vista, what they did with XP. On XP, Microsoft only provided version 1.1 of OpenGL, and third party companies were left to provide additional versions and support. With Vista, Microsoft made the decision to provide support up until 1.4. And, again, other people would have to give the additional support.

Not really. It's a little more complex than that. In XP, while Microsofts OpenGL support was obsolete beyond belief, the interface to it - the ICD interface - was well documented for hardware manufacturers.

In Vista, the LDDM compatible interface to the Aero desktop compositor is not documented, and LDDM is more complex than the old XP driver ICD interface model (due to WGF, but also due to TC related issues). In other words, external vendors were not able to support OpenGL, even if they wanted to. They still cannot to the full extend (ie. fully composited Aeroglass OpenGL), but a compromise solution was found (ie. uncomposited window, without requiring to turn off Aero entirely).

This solution is good for me, as it is acceptable for both games and professional CAD software. Although it would be nice, if we could eventually get a full LDDM compatible OpenGL driver for Aero.

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I still don't understand why Microsoft 'thinks' they have a decision in impeding OpenGL in Vista. If Nvidia or ATI write their drivers to circumvent anything Microsoft has put in place, won't that just enable full support for OpenGL?

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Original post by oconnellseanm
If Nvidia or ATI write their drivers to circumvent anything Microsoft has put in place, won't that just enable full support for OpenGL?
If that were to happen, MS could refuse to sign the drivers, and I gather that the current state of Vista is that no unsigned drivers are allowed without explicitly booting into a special mode.

Besides, MS haven't directly done anything to destroy OpenGL, in much the same way that Apple haven't directly done anything to prevent Windows from running on the Mactels. It's just that the technology was built in such a way (intentionally or not) that the state of affairs is as such.

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Original post by oconnellseanm
So do most people in the industry. Check out the thread at OpenGL.org
Personally I think they're idiots, excluding the few guys from 3D Labs, who have been most helpful in providing actual facts, and not making up bullshit about the performance numbers and not using a popular website to spread Fear, Uncertainty, and Doubt.

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Indeed, there is some correct information in that thread, but the signal to noise ratio is terrible, people mouthing off left and right about MS being evil and how we should all just use Linux and blah blah blah.

Most of the people posting certainly arent in the industry, I can tell you that much..

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well, this is just my opinion, it maybe alittle bit strange.
MS won't be able to do anything that breaks support for existing Applications and Games(or makes it harder for developers to make Apps or Games).
OpenGL has alot of supporters(Carmack, NVidia, etc...), MS can't just leave all of them behind.
so, I think they'll change their mind right before releasing Vista, and if this didn't happen, we can use an uncomposited window after all :)

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Original post by Expandable
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Original post by Xeee
OpenGL has alot of supporters(Carmack, NVidia, etc...),


Though Carmack is thinking about switching to Direct3D, AFAIK...


Who knows, but if he is planning on doing stuff with Cell phones and PS3 ect... DX wouldn't be a wise choice. I know in the latest PC gamer he said xbox 360 is their target platform now not PC... They also are going to make their games for PS3. So DX would seem a waste of time IMO if you want to sell games on PS3. I for one am sick of hearing about PC game companies selling out to the console market and seem to be ditching the PC crowd. If PC games are done with then I will be done playing games. Sorry for rant. :(

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Eh, the API simply doesn't matter that much anymore. Flipping from one to the other is easy now, with the slight catch of being forced to switch up all your shaders. Surely you don't think that Doom 3 on Xbox and Quake 4 on X360 are running OpenGL?

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Original post by MARS_999
I for one am sick of hearing about PC game companies selling out to the console market and seem to be ditching the PC crowd. If PC games are done with then I will be done playing games. Sorry for rant. :(


You needn't be afraid of that. Epic are still targetting PC's as their primary platform. And regarding that article, if I remember correctly, their *primary* target platform is now XBox360. However, due to the nature of it, it is easier to port from there to PC than developing for PC and then porting to 360.

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Original post by rick_appleton
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Original post by MARS_999
I for one am sick of hearing about PC game companies selling out to the console market and seem to be ditching the PC crowd. If PC games are done with then I will be done playing games. Sorry for rant. :(


You needn't be afraid of that. Epic are still targetting PC's as their primary platform. And regarding that article, if I remember correctly, their *primary* target platform is now XBox360. However, due to the nature of it, it is easier to port from there to PC than developing for PC and then porting to 360.


Great! So that means we PC users will have to settle for crappy graphics.

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Original post by rick_appleton
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Original post by MARS_999
I for one am sick of hearing about PC game companies selling out to the console market and seem to be ditching the PC crowd. If PC games are done with then I will be done playing games. Sorry for rant. :(


You needn't be afraid of that. Epic are still targetting PC's as their primary platform. And regarding that article, if I remember correctly, their *primary* target platform is now XBox360. However, due to the nature of it, it is easier to port from there to PC than developing for PC and then porting to 360.


Great! So that means we PC users will have to settle for crappy graphics.


How do you figure? The graphics we have now are great, so you are implying they will get worse in the future?

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Original post by cherryhouse
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Original post by oconnellseanm
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Original post by rick_appleton
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Original post by MARS_999
I for one am sick of hearing about PC game companies selling out to the console market and seem to be ditching the PC crowd. If PC games are done with then I will be done playing games. Sorry for rant. :(

You needn't be afraid of that. Epic are still targetting PC's as their primary platform. And regarding that article, if I remember correctly, their *primary* target platform is now XBox360. However, due to the nature of it, it is easier to port from there to PC than developing for PC and then porting to 360.

Great! So that means we PC users will have to settle for crappy graphics.

How do you figure? The graphics we have now are great, so you are implying they will get worse in the future?

He's implying that if Epic continue to target Xbox 360 (a static platform), the Unreal Engine will be bound to the 360's hardware constraints, and won't take full advantage of the power of PCs which will evolve over the lifetime of the 360.

Personally, I don't think that will happen, even if two versions of the engine are required in the end: an almost fully-developed Xbox 360 version, and a more open, less constrained PC version.

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That's not a very likely case. Look at pretty much all the other games ported from console to pc, they have different graphic engines, or at least upgraded to look better. Grand theft auto:sa for example, halo is another example. List goes on. You have to remember, a lot of reasons games are created for console, then later for pc is because they do have better quality games for pc due to the expanding resource limit on pc's compared to consoles. The developers aren't brain dead, they are paid to think about these kinds of things.

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      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 two samples, asteroids performance benchmark and example Unity project that uses Diligent Engine in native plugin.
      AntTweakBar sample is Diligent Engine’s “Hello World” example.

       
      Atmospheric scattering sample is a more advanced example. It 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 and Android platforms. Direct3D11, Direct3D12, OpenGL/GLES backends are now feature complete. Vulkan backend is coming next, and support for more platforms is planned.
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