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OpenGL Re-Learn DX10?

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Hey guys, I've been wanting to ask this question for a while, it might've already been discussed but I found no reference of it, sorry. If I learn DX9 (D3D), would I have to relearn DX10 when it comes out? What I mean is, would it have a completely different API? Or would it be the same (obviously with add ons). I'm sorry if I dont state this clearly, please ask me to elaborate if I didn't. This is a reason why I want to use OpenGL instead, but then again I'm not very fond of OpenGL's extensions.

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DirectX 10 won't be in your hands for a very long time. Anyway, as a software developer you will have to learn new languages and APIs for the rest of your life (the most valuable thing you can learn is how to learn, then you'll be infinately adaptable). Only the people working on DX10 will be able to tell you exactly how much the API will change, but if you accept the fact that, as a software developer, you'll have to frequently learn new things, you'll be able to handle it when it comes. That said, they're planning on some big changes, that's not to say your DX9 experience won't be useful when DX10 comes around though.

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Learning DX9 will help you out with DX10 *a lot*. There are changes in DX10, but all can be taken in stride if you already know the fundamentals of it. I recommend taking a look at some intro DX9 tutorials and getting familiar with the API. Then, when the beta for DX10 comes out, get it and start looking at that stuff. It shouldn't be too long at all.

If you don't really know too much about graphics programming, now would be a perfect time to pick up the fundamentals of it (underlying math and techniques). Remember that in D3D10, there will be no FFP, so you will have to write all of your own shaders, so you must have the necessary background for that, too.

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if you accept the fact that, as a software developer, you'll have to frequently learn new things, you'll be able to handle it

That's some good advice there. DirectX10 is a WindowsVista only component, so you won't see it in a 'final' form until it's released (currently 2H-06). You've got *plenty* of time to learn DX9. Learning DX9 will not be a waste of time.

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Remember that in D3D10, there will be no FFP, so you will have to write all of your own shaders, so you must have the necessary background for that, too.

If you're learning D3D9, you really want to focus on the programmable pipeline. If there is one implementation skill that you'll be able to take from D3D9->D3D10 it'll be the concepts/methods of the programmable pipeline [smile]

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when the beta for DX10 comes out, get it and start looking at that stuff. It shouldn't be too long at all.

A relevant quote from Chuck Walbourn:
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The runtime components will be inbox for Windows Vista Beta 2. The Direct3D 10 documentation, samples, headers, libs, reference rasterizer, etc will be entering public beta in a DirectX SDK release in sync with Beta 2.

Which basically leaves the question as to when Windows Vista Beta 2 is out [wink]. I'll refrain from commenting, but I've seen enough talk online that seems to be fairly logical/'accurate'.

hth
Jack

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Thanks guys, of course I understand learning new APIs, I was just curious if the API would change all that much (functions, etc.) But you're right, there's lots of time anyways.

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Original post by jollyjeffers
Quote:
Remember that in D3D10, there will be no FFP, so you will have to write all of your own shaders, so you must have the necessary background for that, too.

If you're learning D3D9, you really want to focus on the programmable pipeline. If there is one implementation skill that you'll be able to take from D3D9->D3D10 it'll be the concepts/methods of the programmable pipeline [smile]

I'd be a little wary of that logic. Not that there's anything wrong with the programmable pipeline, but I've noticed a fair number of people coming up who don't understand what the programmable pipeline is, because they don't understand what preceeded it and what precisely is replaces. I'm not saying you should spend a huge amount of time working with fixed function, but get to know it as well.

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Original post by Promit
Quote:
Original post by jollyjeffers
Quote:
Remember that in D3D10, there will be no FFP, so you will have to write all of your own shaders, so you must have the necessary background for that, too.

If you're learning D3D9, you really want to focus on the programmable pipeline. If there is one implementation skill that you'll be able to take from D3D9->D3D10 it'll be the concepts/methods of the programmable pipeline [smile]

I'd be a little wary of that logic. Not that there's anything wrong with the programmable pipeline, but I've noticed a fair number of people coming up who don't understand what the programmable pipeline is, because they don't understand what preceeded it and what precisely is replaces. I'm not saying you should spend a huge amount of time working with fixed function, but get to know it as well.

If you don't intend to be using D3D9 for a long duration of time, I'm not quite sure why one would learn a deprecated technology such as the FFP. Many of the challenges people have with the programmable pipeline are the result of them not understanding fundamental concepts of graphics programming. The FFP allows for this lack of knowledge, which is exactly where people get into trouble. For example, learning how to use the FFP to enable fog (for instance) isn't going to help you implement a fog shader.

I don't think that the PP is necessarily replacing the FFP, because for a while now, the FFP has existed more or less as a library of shaders that D3D just set up for you. Of course, the API for this library wasn't the best, as it was layered directly into the other API (as a result from when programmable shaders weren't available).

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Is it 100% confirmed they are going to cut out the FFP? If it is, I hope there will be some alternative API rolled in to replace the FFP...

Shaders are all nice and dandy, but there is so much funtionality stowed away in the FFP which is gonna require additional effort to code in shaders (anything having to do with multiple texture stages, alpha operations etc). As an alternative, more powerful API for the pipeline shaders are just fine, but if it's gonna be the complete replacement for the FFP it needs more work... A new API shouldn't make things more complex by taking away levels of abstraction IMHO.

The FFP for example works out of the box, while you'll have to code your own shader to get started with DX10, at least from the sound of it. That's not too much work, but a number of simple default shaders, that perform the same functionality as much used FFP settings, would really be nice... especially for beginners who want to focus on getting things rendered in the first place and NOT HOW on earth to render them.

But since...

Quote:
...the FFP has existed more or less as a library of shaders that D3D just set up for you.


...I guess they'll at least release these FFP shaders for use to get started with. Come to think of it, how will DX10 support non-DX9 (< ps2) hardware? Guess not at all then, right?

[edit]

Seems I got worried again for nothing, going from the PDC talk on ZBuffer. Since at least Vista will still ship with DX9, we can still use it, right? ZMan also said in the article that no DX10 hardware exists yet, so I reckon it's gonna be 1 or 2 years before it gets really accepted and used, no?

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Guest Anonymous Poster

Hi,

Biggest changes in DX came around DX5-DX7 to DX8. After DX8 the changes has been more like refining and tuning little things. Difference between DX9 and DX8 aren't so big anymore.

When ever there has been a new DX available, I have upgraded my DX part of the code and it has been worth it.

Cheers






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Thanks for your feedback, since I'm now also very much interested in this :)

However, I read that DX10 will completely break backward compatibility with DX9 (introducing the geometry shader and numerous other features), so I guess we're looking at something similar to the DX5-DX7 to DX8 shift. Would anyone happen to have some good links on what is going to change with DX10 exactly, so I can read it firsthand? :)

On a releated note, I just came across Shadergen for OpenGL, which converts OpenGL FFP settings to a shader for you, complete with compatibility checks against OpenGL versions and video drivers. Does anyone know if something similar exists for DirectX / HLSL? It looks like a great tool, even more so with DX10's reported lack of the FFP.

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Just to re-iterate and to express my views on the subject.
Learning an API is trivial, what is important though is that you understand the fundamentals such as the pipeline and how everything ties in and some hardware knowledge. With this knowledge you can extend and use different API's and still be comfortable.

The reason I am saying this is the following...
When coding anything you need to understand what you are coding. Take for example a simple direct3d app. You know the rendering pipeline goes in the following order

Stage #1 -> Input Vertex data...
Stage #2 -> Transform and Lighting
Stage #3 -> Clipping/ Culling/ Rasterization
Stage #4 -> Pixel processing
Stage #5 -> Testing (Alpha, depth, stencil...)
Stage #6 -> Output to FrameBuffer

When you are comfortable with this knowledge and how each stage interacts with another you can easily understand that in the start of your app (excluding initializing the rendering device etc...) you need to store your data in a vertex buffer or a storage buffer. You then can using a vertex shader in the vertex processing stage do transform and lighting etc.

PS: It's always good to study the theory and then look at the implementation as it always works well when you understand what you want to do and when it comes to learning a new API you basically just bridge/extend your knowledge and plug in new parts of the pipeline like geometry shaders and input semantics...

I hope this helps.
Take care.

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Original post by remigius
However, I read that DX10 will completely break backward compatibility with DX9 (introducing the geometry shader and numerous other features)
As a general concept, introducing new features never breaks backwards compatability - it's removing old features that does that.

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Would anyone happen to have some good links on what is going to change with DX10 exactly, so I can read it firsthand? :)
Seek out the Meltdown 2005 slides, or the PDC stuff. They contain a decent overview of what's changing.

In short summary: learning DX9 with a focus on the programmable pipeline (instead of the FFP) will put you in good stead for DX10. Names of functions will change, but the important stuff - the way the API gets used - will be familiar. (Learning an API shouldn't mean memorising the function names anyway).

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Original post by superpig
As a general concept, introducing new features never breaks backwards compatability - it's removing old features that does that.


For good measure I'll submit that the accursed Java foreach loop almost did. In regard to platform changes, new features CAN render old code obsolete or disfunctional when the behaviour of statements/API calls changes, failing to replicate the old behaviour using the new features/approaches.

This might well be the case with the introduction of geometry shaders, as this fundamentally alters the pipeline. It shouldn't have to be breaking backward compatibilty, but it just might be. Just to expand your general concept :)

Quote:
In short summary: learning DX9 with a focus on the programmable pipeline (instead of the FFP) will put you in good stead for DX10. Names of functions will change, but the important stuff - the way the API gets used - will be familiar.


I agree, but the current PP still is not as 'fleshed out' as the FFP. When doing some texture blending I can use the texture stages in the FFP without any additional effort, but with the PP I'll have to write a new shader from scratch (or am I missing something here?). It's inconvenient, but it's not my main problem with solely focussing on the PP.

The FFP serves as a layer of abstraction between the application and the graphics pipeline. Setting lights, fog or texture states on a device will perform some documented behaviour, which is easy to understand and predictable. When you're working directly with shaders, you don't know what's going on inside the shader until you take a look at it, which makes it harder to understand, predict and re-use than the FFP.

It may be a purist's discussion, but I feel this is a downside to the pure-PP approach. This might be where SAS compliant fx files come in, but information on this is a bit sketchy from what I've seen... Or maybe I didn't look in the right place and someone also has a link for that? :)

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With regards to the push for use of the PP - in all fairness it's not a new concept. we've had 4 (5?) years of being able to use both FF and PP, and it was always a matter of time before it became the dominant feature.

For absolute beginners to graphics theory I can see why the FF might be useful - you can, within reason, get a long way without knowing much about the inner workings of graphics algorithms. However, this is probably a bad thing - knowing how something works can be quite important (at the very least, a useful skill) and hiding it all away can introduce other problems.

My favourite example of this is the texture cascade / fixed function texture blending. I *hate* that with a passion. It effectively masks a simple tree of possibilities and, when written down, isn't that complicated... but I find it ridiculously slow (development time, not runtime!) to work with. Hardware support for it is fairly good, but it's far from perfect - so you still have to be careful using any obscure components in your code. OTOH you can usually express exactly what you want very concisely, very clearly, using a pixel shader. You write it how you want to, in a way that makes more sense than setting 10-20 render states and leaving the implementation details hidden.

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When you're working directly with shaders, you don't know what's going on inside the shader until you take a look at it, which makes it harder to understand, predict and re-use than the FFP.

Strictly my opinion of course, but I completely disagree with this statement. I got pointed to this article yesterday, which shows a way in which to build lighting models from fundamental component functions. Using the effect interface you can then wrap it all up with a single technique name: OrenNayarWithBlinnPhongSpecular. You call a SetTechnique() in your code and you know what you're going to get. Strikes me as much more elegant than all the configuration and potential problems you can get via the render state system.


One thing to bare in mind though is that Microsoft are aware that a lot of people are fairly familiar with the FF method, and given the huge differences with D3D10 they're bound to include some stuff to help people migrate. It's simply not in their interest to kick everyone back to square-1 [smile]

Quote:
Since at least Vista will still ship with DX9, we can still use it, right?

You'll still be able to run applications compiled against previous versions of DirectX. Microsoft would be shooting themselves in the foot if they culled that much backwards compatability. Whilst it might not be the preferred route, developing for current 9.0c under WinXP should yield an executable that is compatable with current OS's as well as Vista. Could well be the best choice for some people.
Quote:
ZMan also said in the article that no DX10 hardware exists yet, so I reckon it's gonna be 1 or 2 years before it gets really accepted and used, no?

Yeah, there's always a transition period. There's even DX9.L thats the Vista-specific version of DirectX9 to consider. As for the DX10 hardware - I'd expect some DX10 parts to be available at time of release, or very soon after it. New OS's tend to drive a new investment in hardware, so for money alone it's good for IHV's to have something ready for us to spend our money on [grin]

hth
Jack

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It is in the interest of both Microsoft as well as the IHV's to have hardware available when a major product that makes extensive use of it is released. I would be surprised if there WASN'T hardware available when Vista launches.

As far as the FFP goes, I think it boils down to what your background is. If you have a graphics theory background, then shaders are much more understandable because you can just type in the math equations you already know. If your background is not in graphics, then the FFP masks away a lot of details that you would normally have to worry about. The downside to this is that the FFP then becomes a black-box, in which you don't really understand what's going on underneath.

For example, say you wanted to blend two textures together based on the alpha value of a material. To do this in a shader, you would just do:

vTextureColor0 * fMaterialAlpha + vTextureColor1*(1.0f-fMaterialAlpha)

This is easy to see conceptually. But doing this in using the FFP requires around 5 or 6 SetSamplerState calls with a ton of different parameters to select the appropriate texture, channel, blending mode, and alpha mode.

One of the reasons for the move to a programmable pipeline was that the moment you start to do anything even remotely complicated in FFP, you easily get mired down in a sea of renderstate settings that takes an expert to configure properly. Not only does the developer need to know the conceptual operation they want to do, but they also need to understand how to translate that into a ton of renderstate settings to get it working.

Seeing that DirectX was originally, and still is intended mainly for graphics professionals, it makes sense for Microsoft to let developers specify their rendering techniques in the way that is most natural to them: graphics theory. The DirectX docs are meant to show professional developers how to implement the graphics techniques they know from a theoretical point of view in the DirectX API. They aren't really meant to teach graphics programming to beginners, although there are some sections of the SDK docs that do cover a few of the basics.

neneboricua

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      Creating Shaders
      While in earlier APIs shaders were bound separately, in the next-generation APIs as well as in Diligent Engine shaders are part of the pipeline state object. The biggest challenge when authoring shaders is that Direct3D and OpenGL/Vulkan use different shader languages (while Apple uses yet another language in their Metal API). Maintaining two versions of every shader is not an option for real applications and Diligent Engine implements shader source code converter that allows shaders authored in HLSL to be translated to GLSL. To create a shader, one needs to populate ShaderCreationAttribs structure. SourceLanguage member of this structure tells the system which language the shader is authored in:
      SHADER_SOURCE_LANGUAGE_DEFAULT - The shader source language matches the underlying graphics API: HLSL for Direct3D11/Direct3D12 mode, and GLSL for OpenGL and OpenGLES modes. SHADER_SOURCE_LANGUAGE_HLSL - The shader source is in HLSL. For OpenGL and OpenGLES modes, the source code will be converted to GLSL. SHADER_SOURCE_LANGUAGE_GLSL - The shader source is in GLSL. There is currently no GLSL to HLSL converter, so this value should only be used for OpenGL and OpenGLES modes. There are two ways to provide the shader source code. The first way is to use Source member. The second way is to provide a file path in FilePath member. Since the engine is entirely decoupled from the platform and the host file system is platform-dependent, the structure exposes pShaderSourceStreamFactory member that is intended to provide the engine access to the file system. If FilePath is provided, shader source factory must also be provided. If the shader source contains any #include directives, the source stream factory will also be used to load these files. The engine provides default implementation for every supported platform that should be sufficient in most cases. Custom implementation can be provided when needed.
      When sampling a texture in a shader, the texture sampler was traditionally specified as separate object that was bound to the pipeline at run time or set as part of the texture object itself. However, in most cases it is known beforehand what kind of sampler will be used in the shader. Next-generation APIs expose new type of sampler called static sampler that can be initialized directly in the pipeline state. Diligent Engine exposes this functionality: when creating a shader, textures can be assigned static samplers. If static sampler is assigned, it will always be used instead of the one initialized in the texture shader resource view. To initialize static samplers, prepare an array of StaticSamplerDesc structures and initialize StaticSamplers and NumStaticSamplers members. Static samplers are more efficient and it is highly recommended to use them whenever possible. On older APIs, static samplers are emulated via generic sampler objects.
      The following is an example of shader initialization:
      ShaderCreationAttribs Attrs; Attrs.Desc.Name = "MyPixelShader"; Attrs.FilePath = "MyShaderFile.fx"; Attrs.SearchDirectories = "shaders;shaders\\inc;"; Attrs.EntryPoint = "MyPixelShader"; Attrs.Desc.ShaderType = SHADER_TYPE_PIXEL; Attrs.SourceLanguage = SHADER_SOURCE_LANGUAGE_HLSL; BasicShaderSourceStreamFactory BasicSSSFactory(Attrs.SearchDirectories); Attrs.pShaderSourceStreamFactory = &BasicSSSFactory; ShaderVariableDesc ShaderVars[] = {     {"g_StaticTexture", SHADER_VARIABLE_TYPE_STATIC},     {"g_MutableTexture", SHADER_VARIABLE_TYPE_MUTABLE},     {"g_DynamicTexture", SHADER_VARIABLE_TYPE_DYNAMIC} }; Attrs.Desc.VariableDesc = ShaderVars; Attrs.Desc.NumVariables = _countof(ShaderVars); Attrs.Desc.DefaultVariableType = SHADER_VARIABLE_TYPE_STATIC; StaticSamplerDesc StaticSampler; StaticSampler.Desc.MinFilter = FILTER_TYPE_LINEAR; StaticSampler.Desc.MagFilter = FILTER_TYPE_LINEAR; StaticSampler.Desc.MipFilter = FILTER_TYPE_LINEAR; StaticSampler.TextureName = "g_MutableTexture"; Attrs.Desc.NumStaticSamplers = 1; Attrs.Desc.StaticSamplers = &StaticSampler; ShaderMacroHelper Macros; Macros.AddShaderMacro("USE_SHADOWS", 1); Macros.AddShaderMacro("NUM_SHADOW_SAMPLES", 4); Macros.Finalize(); Attrs.Macros = Macros; RefCntAutoPtr<IShader> pShader; m_pDevice->CreateShader( Attrs, &pShader );
      Creating the Pipeline State Object
      After all required shaders are created, the rest of the fields of the PipelineStateDesc structure provide depth-stencil, rasterizer, and blend state descriptions, the number and format of render targets, input layout format, etc. For instance, rasterizer state can be described as follows:
      PipelineStateDesc PSODesc; RasterizerStateDesc &RasterizerDesc = PSODesc.GraphicsPipeline.RasterizerDesc; RasterizerDesc.FillMode = FILL_MODE_SOLID; RasterizerDesc.CullMode = CULL_MODE_NONE; RasterizerDesc.FrontCounterClockwise = True; RasterizerDesc.ScissorEnable = True; RasterizerDesc.AntialiasedLineEnable = False; Depth-stencil and blend states are defined in a similar fashion.
      Another important thing that pipeline state object encompasses is the input layout description that defines how inputs to the vertex shader, which is the very first shader stage, should be read from the memory. Input layout may define several vertex streams that contain values of different formats and sizes:
      // Define input layout InputLayoutDesc &Layout = PSODesc.GraphicsPipeline.InputLayout; LayoutElement TextLayoutElems[] = {     LayoutElement( 0, 0, 3, VT_FLOAT32, False ),     LayoutElement( 1, 0, 4, VT_UINT8, True ),     LayoutElement( 2, 0, 2, VT_FLOAT32, False ), }; Layout.LayoutElements = TextLayoutElems; Layout.NumElements = _countof( TextLayoutElems ); Finally, pipeline state defines primitive topology type. When all required members are initialized, a pipeline state object can be created by IRenderDevice::CreatePipelineState() method:
      // Define shader and primitive topology PSODesc.GraphicsPipeline.PrimitiveTopologyType = PRIMITIVE_TOPOLOGY_TYPE_TRIANGLE; PSODesc.GraphicsPipeline.pVS = pVertexShader; PSODesc.GraphicsPipeline.pPS = pPixelShader; PSODesc.Name = "My pipeline state"; m_pDev->CreatePipelineState(PSODesc, &m_pPSO); When PSO object is bound to the pipeline, the engine invokes all API-specific commands to set all states specified by the object. In case of Direct3D12 this maps directly to setting the D3D12 PSO object. In case of Direct3D11, this involves setting individual state objects (such as rasterizer and blend states), shaders, input layout etc. In case of OpenGL, this requires a number of fine-grain state tweaking calls. Diligent Engine keeps track of currently bound states and only calls functions to update these states that have actually changed.
      Binding Shader Resources
      Direct3D11 and OpenGL utilize fine-grain resource binding models, where an application binds individual buffers and textures to certain shader or program resource binding slots. Direct3D12 uses a very different approach, where resource descriptors are grouped into tables, and an application can bind all resources in the table at once by setting the table in the command list. Resource binding model in Diligent Engine is designed to leverage this new method. It introduces a new object called shader resource binding that encapsulates all resource bindings required for all shaders in a certain pipeline state. It also introduces the classification of shader variables based on the frequency of expected change that helps the engine group them into tables under the hood:
      Static variables (SHADER_VARIABLE_TYPE_STATIC) are variables that are expected to be set only once. They may not be changed once a resource is bound to the variable. Such variables are intended to hold global constants such as camera attributes or global light attributes constant buffers. Mutable variables (SHADER_VARIABLE_TYPE_MUTABLE) define resources that are expected to change on a per-material frequency. Examples may include diffuse textures, normal maps etc. Dynamic variables (SHADER_VARIABLE_TYPE_DYNAMIC) are expected to change frequently and randomly. Shader variable type must be specified during shader creation by populating an array of ShaderVariableDesc structures and initializing ShaderCreationAttribs::Desc::VariableDesc and ShaderCreationAttribs::Desc::NumVariables members (see example of shader creation above).
      Static variables cannot be changed once a resource is bound to the variable. They are bound directly to the shader object. For instance, a shadow map texture is not expected to change after it is created, so it can be bound directly to the shader:
      PixelShader->GetShaderVariable( "g_tex2DShadowMap" )->Set( pShadowMapSRV ); Mutable and dynamic variables are bound via a new Shader Resource Binding object (SRB) that is created by the pipeline state (IPipelineState::CreateShaderResourceBinding()):
      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.
    • By LifeArtist
      Good Evening,
      I want to make a 2D game which involves displaying some debug information. Especially for collision, enemy sights and so on ...
      First of I was thinking about all those shapes which I need will need for debugging purposes: circles, rectangles, lines, polygons.
      I am really stucked right now because of the fundamental question:
      Where do I store my vertices positions for each line (object)? Currently I am not using a model matrix because I am using orthographic projection and set the final position within the VBO. That means that if I add a new line I would have to expand the "points" array and re-upload (recall glBufferData) it every time. The other method would be to use a model matrix and a fixed vbo for a line but it would be also messy to exactly create a line from (0,0) to (100,20) calculating the rotation and scale to make it fit.
      If I proceed with option 1 "updating the array each frame" I was thinking of having 4 draw calls every frame for the lines vao, polygons vao and so on. 
      In addition to that I am planning to use some sort of ECS based architecture. So the other question would be:
      Should I treat those debug objects as entities/components?
      For me it would make sense to treat them as entities but that's creates a new issue with the previous array approach because it would have for example a transform and render component. A special render component for debug objects (no texture etc) ... For me the transform component is also just a matrix but how would I then define a line?
      Treating them as components would'nt be a good idea in my eyes because then I would always need an entity. Well entity is just an id !? So maybe its a component?
      Regards,
      LifeArtist
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