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DX11 high over 3d engine design

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Hi all,


For the last years (with pauses) I've been working on my own C++ 3d engine.

I'm using D3D9 for rendering up till today (DX11 later now, gathering knowledge and experience first).

 

Everything's done on a hobby basis and last months I've been working myself through basics, like brushing up C++ and 2d games.

For who's interested: http://www.crealysm.com/games/Asteroidz%20v0.3.zip.

 

With all knowledge gained and articles/ books read, I'm rethinking my high over 3d engine design.

I would really like to hear your thoughts and gather input, before adding more and more functionality.

 

Below I've tried to explain 'the basic layout'.

Any input is really appreciated, what would you do, what do you think is wrong as initial design etc.

 

Next steps will be

- implemening correct usage of 'const' (when passing objects by reference)

- adding an entity manager/class structure (with vectors instead of dynamic arrays, which I now do for the 'static scene')

- rethink/ design classes using inheritance, not done up till now

- make some simple demo's along the way, adjust and improvise along the way

 

(my apologies for using text, the VS class diagram doesn't work somehow, something about keys being added already)

 

TOP LEVEL: NAMESPACES (including classes, .....)

 

- d3drenderer (camera, font, light, mesh, mesh instance, scene, shader, skybox)

- dxinput

- dxmath (boundingbox, struct likes vectors, materials, vertices)

- game (player)

- general (FPS/ timer)

- IO (fileformat for scenes, classes for light, mesh, meshinstance etc., api independent)

- math (structs API independent, vector, indices for materials/ submeshes, colors etc.)

- renderer (scenegraph class and structs for effects/shaders, lights, materials, meshes, instances etc.)

- audio (FMod audio wrapper, class)

Edited by cozzie

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Here's my honest opinion. Focus on results, nothing else matters (especially correct usage of const). You see, all the end user is going to see is the results. Most likely nobody else but you will ever look at your source code, so don't waste time making it obsessively neat.

 

I downloaded and tried out your asteroidz game. Pretty decent asteroids game, good enough graphics. Very annoying that I ran out of ammunition so quickly. There was a sound bug when your shot hits two asteroids in rapid succession the sound effect is not played twice as I would have expected.

 

Overall, not a very impressive showing of DX9, could just as easily have been coded in SDL or WinGDI, but a good solid game and I spent about 5 minutes using it before I got bored (I reached 9th place on scoreboard).

Edited by Steve_Segreto

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Hi steve.
Thanks for your input and testing. Nice to hear, I'll do some changes in asteroidz v0.4.

The game was honestly just to see if I can finish somehing, no special d3d at all. I'll post a short demo of my engine next week.
On the engine side I'll just go on adding new cool stuff, maintaining clear code/structure, but not as a goal itself, thanks for that note.
Maybe I should also try to finish some simple demo using my engine, just to see how that goes (instead of blind staring at the structure/ design).

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Here's my honest opinion. Focus on results, nothing else matters (especially correct usage of const). You see, all the end user is going to see is the results. Most likely nobody else but you will ever look at your source code, so don't waste time making it obsessively neat.

I think you need to take this in context - results are what the end user will see, for sure.  However, if you are making an engine, that means you are planning on re-using it on more than one project.  That means that your end users will actually be other developers (or yourself if you keep it as a hobby).  In that case, I would highly, highly recommend going through the exercises that you are describing here and consider different aspects and designs that you could implement.

 

This makes you think more about how you are doing things, gives you more and more experience with the language that the engine is written in, and helps you learn more about the API you are using.  These benefits may not be tangible in the end result of a rendered frame, but they will certainly be tangible in your development experience as well as your debugging of issues during development.  So I would agree with Steve that output matters, but disagree that it is the only thing you should focus on!

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think you need to take this in context - results are what the end user will see, for sure. However, if you are making an engine, that means you are planning on re-using it on more than one project. That means that your end users will actually be other developers (or yourself if you keep it as a hobby). In that case, I would highly, highly recommend going through the exercises that you are describing here and consider different aspects and designs that you could implement.

This makes you think more about how you are doing things, gives you more and more experience with the language that the engine is written in, and helps you learn more about the API you are using. These benefits may not be tangible in the end result of a rendered frame, but they will certainly be tangible in your development experience as well as your debugging of issues during development. So I would agree with Steve that output matters, but disagree that it is the only thing you should focus on!


^ This, end result obviously matters, but if you write bad code, it makes it hard to add features to the game/engine, and it also makes it difficult to bring on new developers. Also bad code begets more bad code. Edited by metsfan

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@Jason/Metsfan; thanks, I also think that having the right base/ design will help me in adding future functionalities.

In this context, can you share your ideas on my highover design?

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Well I hate to take the ratings hit, but I think people who give you the opinion to work on your game as an engine don't ship many products.

 

I won't rate you down, as I think it is productive to discuss counter opinions - so I would also suggest that others don't rate you down either.  To be perfectly honest, I don't work in the games industry, so I haven't shipped any games.  I have however build and delivered many diverse applications that use 3D rendering functionality.  So you are right, I can't speak to game development, but I most certainly can speak to software development that utilizes reusable rendering routines and algorithms (i.e. an engine).

 

So are you implying that you don't have an engine?  You just work on one project, and when its time for another project you just take the existing project and modify it?  What if you find a bug in your rendering routines - do you have to go back and make the same changes to a bunch of different projects?

 

It seems a bit silly to me to make the leap that anyone that tries to properly design a reusable library somehow isn't successful at delivering the end product.  In fact, I would say the opposite - having discipline and considering a design aspect of a library has always driven higher productivity in my experience.  You mileage may vary, but when you have to support many simultaneous and different projects with some common functionality, then I think it only makes sense to consider that common functionality as an engine...

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Well I hate to take the ratings hit, but I think people who give you the opinion to work on your game as an engine don't ship many products.

 

I won't rate you down, as I think it is productive to discuss counter opinions - so I would also suggest that others don't rate you down either.  To be perfectly honest, I don't work in the games industry, so I haven't shipped any games.  I have however build and delivered many diverse applications that use 3D rendering functionality.  So you are right, I can't speak to game development, but I most certainly can speak to software development that utilizes reusable rendering routines and algorithms (i.e. an engine).

 

So are you implying that you don't have an engine?  You just work on one project, and when its time for another project you just take the existing project and modify it?  What if you find a bug in your rendering routines - do you have to go back and make the same changes to a bunch of different projects?

 

It seems a bit silly to me to make the leap that anyone that tries to properly design a reusable library somehow isn't successful at delivering the end product.  In fact, I would say the opposite - having discipline and considering a design aspect of a library has always driven higher productivity in my experience.  You mileage may vary, but when you have to support many simultaneous and different projects with some common functionality, then I think it only makes sense to consider that common functionality as an engine...

 

I also don't work in the games industry, so I personally haven't shipped any games either. My understanding of the engine space is limited to Microsoft platforms, specifically directX. I develop a game in my spare time. I hope to one day make money from the game I develop, but of course I haven't, mainly because I work alone and I don't move quickly enough to capitalize on any markets. :(

 

I've been working on my hobby game for about 5 years, in that time Microsoft (which is where my full-time job is ironically), has changed the directX APIs significantly. I haven't had time to adapt, simply because I'm trying to get my original game finished. I would imagine that a slightly larger team (< 100 people) might actually be able to crank out a shipping game product in less than a years time with a certain degree of quality and make some money from it.

 

My opinion is that if they spent any extra time doing "engine" work they would both lose that slim chance to make money and still not create the re-usability they are after as the industry would have passed them by.

 

My opinion is that larger teams (> 100 people?) could make a living out of developing engines, either as middleware or for a platform with reasonable (3-5 year) longevity. In that case, the investment of time and energy in perfecting a usable engine *might* actually pay off for those larger teams.

 

However, for the hobbyist, I would not recommend wasting any time in crafting an engine or designing for reusability or future use. The hobbyist in my opinion should be obsessively focused on just producing a result and getting it to market (even if its alpha), so they can MAKE MONEY from it :)

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The dilemma seems clear to me and is something I run into often.
I solve it very pragmatically:

- I work on my engine, keeping and expanding it in a structured way (keeping reusage in the back of my head)
- since it doesn't deliver direct results, when I have a difficult challenge, I make a fairly simple game to get some results and experience in gameplay (not even using the engine :))

The 2nd even helps me indirectly with challenges I face in my engine.
For example, I was stuck with my flexible point light management for weeks, so I made 'Asteroidz' and actually finished it. This gives me new experience on gameplay functions, audio etc.. And luckily yesterday I found the solution for my point light 'challenge', so now I can get into that and improve my engine. Between all this I try to read books and articles which can give me knowledge on both fields.

All from a hobby perspective for now. But from my daily job (not programming) I have quite some project and product management experience, which drives me to doing preparations and in this case makes me want to make a good design of the engine. Combine that with an upcoming 2 week holiday with just an iPad, some ibooks, a paper and pen... Makes me think, lets rethink the design of the engine, highover. What should it be able to do? How to split this in usefull namespaces? Including which classes and inheritances? Etc.

I could actually copy my timer (FPS management/ time delta) class including all functions, 1 to 1 directly to my Asteroidz game, saving me time. This also motivates me to have my engine include independent classes and parts, so I can reuse them anywhere (as far as possible of course). The same goes for my audio namespace/ classes (FMOD wrapper) and (dx)input wrapper.

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Is it a requirement for your engine to be cross-platform? If so, make sure to spend some time on creating platform independent abstractions for rendering and audio (including shaders .... HLSL is platform/render API specific).

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For directx will do, I'm trying to make my scenegraph, object, lights, scene etc. Classes API independent and have inherited classes to be able to use them for d3d. I think FMOD should be fairly simple if I move to another platform (a few other parameters).
Basically for now all d3d (keeping in mind upgrading to dx11) and where possible having data structures D3D independent

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However, for the hobbyist, I would not recommend wasting any time in crafting an engine or designing for reusability or future use. The hobbyist in my opinion should be obsessively focused on just producing a result and getting it to market (even if its alpha), so they can MAKE MONEY from it smile.png

 

I think you leave out an important point. See, there is hobbyists like me (well at least there is one), who don't have any skills in making even simply 3d graphics, and (for personal reasons) aren't willing to work in a team in their free time to create a game. What have we left to do? We could eigther write a game using shitty placeholder or ripped graphics, but we still won't be able to "sell" the game. I rather write my own engine, and even if it won't be something practical to make money off of, I at least HAD FUN creating it. Programming, unless you plan on making a living off of, shouldn't be all about the money, should it? How could something be a waste of time if you enjoyed doing it, let alone learned a few things from it?

 

Plus, even if the "industry passes you by" as you design an engine, you still get more reusability than if you just design game for game and only pick out some selected reusable components. Sure, you'll be missing some "state of the art" features, but hell - its better than having to basically start from scratch every time you start a new game. You can still improve your "engine" more easily than if you just built game after game using the "latest technologies". At least IMHO.

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@Steve: I think you are mixing two arguments, and that we are agreeing more than disagreeing.  Your experience is that you started out with one API (I guess D3D9) and now there is D3D11.1 - so your efforts are socked into the D3D9 level of effects.  If you were using a well designed engine, the pain of upgrading to a new API would be significantly decreased.  That is the whole point of an engine, to decouple the game itself from the reusable parts.  On a side note, I don't think there is any need to update in this case, as there are still quite a few D3D9 based games being released...

 

One other point that I wanted to make was regarding hobbyist vs. indie vs. professional (Juliean touched on this too).  If you are working on something as a hobbyist, then by definition you are doing it because you like the topic and want to do it.  If you are trying to create a product and sell it, then you are more like an indie, where you are making more of an investment and want to get monetary returns on it.  And of course, the professional makes their full-time paycheck from working in the area.

 

I have personally been a hobbyist for a very long time, and moved into doing professional work more recently - skipping the indie stage.  It sounds to me like you are more focused on being an indie developer, which takes a totally different perspective than a hobbyist.  The OP is looking for perspectives on hobbyist development, so I still think he should lean towards developing an engine as a learning exercise.  He clearly seems motivated enough to knock out a few games here and there, so it is also clear he is learning from doing.  I say, keep it going and enjoy the ride.

 

If you are having trouble finishing your game, is it because you don't have enough time to put on the project, or something more like feature creep?  Identify what the problem is, and take steps to handle it!  I want to see your game on the (digital perhaps) store shelves!

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      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 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.
    • By kan123
      Hello,
      DX9Ex. I have the problem with driver stability in time of serial renderings, which i try to use for image processing in memory with fragment shaders. For big bitmaps the video driver sometimes becomes unstable ("Display driver stopped responding and has recovered") and, for instance, if the media player runs video in background, it sometimes freezes and distorts. I tried to use next methods of IDirect3DDevice9Ex:
      SetGPUThreadPriority(-7);
      WaitForVBlank(0);
      EvictManagedResources();
      with purpose to give some time for GPU between scenes, but it seems to be has not notable effect in this case. I don't want to reinitilialize subsystem for every step to avoid performance loss.
      So, my question is next: does some common practice exists to avoid overloading of GPU by running tasks? Many thanks in advance.
       
    • By AxeGuywithanAxe
      I wanted to see how others are currently handling descriptor heap updates and management.
      I've read a few articles and there tends to be three major strategies :
      1 ) You split up descriptor heaps per shader stage ( i.e one for vertex shader , pixel , hull, etc)
      2) You have one descriptor heap for an entire pipeline
      3) You split up descriptor heaps for update each update frequency (i.e EResourceSet_PerInstance , EResourceSet_PerPass , EResourceSet_PerMaterial, etc)
      The benefits of the first two approaches is that it makes it easier to port current code, and descriptor / resource descriptor management and updating tends to be easier to manage, but it seems to be not as efficient.
      The benefits of the third approach seems to be that it's the most efficient because you only manage and update objects when they change.
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