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OpenGL A method to Gain the Z buffer, Device independent

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I forget to write the subject in my last thread, faint, so I have to post it again here: It's nearly a mission imporsible to gain the data in Z-Buffer directly with Direct9. Normally, you can set a RenderTarget, write a Pixel Shader which outputs Z/W per pixel. Or you can depend on Z-Buffer Readable graphic cards, and copy the z-buffer surface to new surfaces. Both of these method are tough to be utilized in a real game engine. I will explain why after I explain my method. My method is based on the fact that if Z buffer works, it should cull those pixels whichs depth are deeper than the corresponding pixels in Z-buffer. So I just test it by writing a bunch of surfaces with different depth to the back buffer with different colors, and acquire the result by render target. The steps are showed as follows: 1. Complete drawing everything that you want the depth. For example: your terrain and your buildings. 2. Replace the RenderTarget with a new surface which are used to read and gain the result later. It should be as small as it should be. I thought 256*128 is quit enough. 3. Draw 256 surfaces in the post projection space with w = 0, z = 1 to 0, color = 256 to 0, namely far to near. Remember to shut lights and textures. 4. Use the render target in your shader, such as a shadow map second pass. Cheer up, you can now get the Depth without an extra pass. There are tricks in step 3: You only need to build a Vertex Buffer once, then you can use it whenever you want to launch the "Depth Drawing"(Lets call this method like this for short). You must use the stencil buffer to accelerate this process. You can decide how the Z value increases through surfaces by what your scene looks like. Because in D3D projection matrix, 33 = F/(F-N), 43 = -FN/(F-N) (F=Far Clip, Near = Near Clip), Depth in the post projection space should equal Zw = F(1 - N (1/Zv))/(F-N). You can figure out this formular on your own, and you can find that Zw in Depth Space (post projection Space) is actually linear to 1/Zv (Zv is the Depth in View Space). As a result , you can set z like this : V1.z = (256.0 / (256.0 - 1.0)) * (1.0 - 1.0/(DOUBLE)(i+1)); So the Z are linear to 1/i (i = 256 to 0). Make sure the Z is in [0, 1], because it is in post projection space of directx(OpenGl is [-1,1],depending on the projection matrix). You can find out in my codes that the surfaces I drawn are not parallel to the Near clip plate, because I use the D3DPT_TRIANGLESTRIP in DrawPrimitive method in order to reduce bandwidth consumption. The surfaces are acctually looks lick overlapping Zs from the top. This trick has an extra benefit that the color values and the depths of pixels are interpolated automatically by the hardware. The result render target will be worked out by the graphic card like this : 1. The surfaces with z increasing are drawn from far to near. 2. Once a surface with less Z passes Z test, it also means it is the first surface pass the Z test. The depth (can gained by the color) of the surface is the closest one to the value in Z-buffer. 3. it writes the stencil buffer to 1, telling the following pixel to skip. As you can see, there are many drawbacks in this method. First, it is highly pixel fill rate comsuming. It can be alleviated partially by making the render target smaller. Second, the precision is very low, because it can only provide 256 grads. You can try gain more grads with more faces, while it will surely consume more fill rate. This method is more suitable for Z correctiong, point z detection, and some other stages that don't require high z accuracy. Getting Z buffer is too tough a job in DX9. It can only be copy to a surface with same size and same format, but how can I use it anyway if they are the same. If you try to use a lockable depth surface, you are doomed. I try this with D16_Lockable and D32_Lockable, and once I lock, the fps drop from 600 to 12, even I unlock it immediatly without doing nothing and even the lock is called before BeginScene. I dont know whether other graphic cards will suffer this problem. The Lockable buffer is not pratical at all because even it can be locked, we have to do format convertion at lease once to gain the data in it, and it may be more slower than just render the scene twice with lights and textures shutted. In my opinion, why didn't the PS provide a register called iDepth, when there are already a oDepth avallable. It's baffling that once a segment get through all the tests and reach the Pixel Shader, it's depth has already been compared with the Z-buffer, and is it so tough to just pass the compare value to PS? Then we can have iDepth. If there is iDepth register(or Semantic) in PS, we can spare the gpu time to calculate z/w in the shadow map algorithm. Moreover, in the second pass of shadow map, we can also spare the gpu time to calcualte and pass the value of z/w in view space again. Newer DX versions have provided much easier way to get access to the depth buffer, however, it's not very pratical to ask out customer to buy a 8800 before buying our game, isn't it? Any people who has any thought about this method, feel free to reply. I am eager to chat about methods to get the Z buffer. codes are shown as follows:(I omit most trivial details) 3.1 Build The Buffer struct TypeRectVertex { enum{fvf = D3DFVF_XYZRHW | D3DFVF_DIFFUSE,}; FLOAT x,y,z,w; D3DCOLOR color; } enum{ numquos = numlevel,//256 numvertices = numquos * 2 +2, vb_size = numvertices * sizeof(TypeRectVertex), }; ZeroMemory(m_VBInMemory, sizeof(TypeRectVertex) * _countof(m_VBInMemory)); _ASSERTE(pd3dDevice); _ASSERTE(numlevel %2 == 0 && numlevel <= 256); const D3DSURFACE_DESC* pSurfaceDesc = DXUTGetBackBufferSurfaceDesc(); if(!pSurfaceDesc) return; FLOAT fWidth = (FLOAT)pSurfaceDesc->Width; FLOAT fHeight = (FLOAT)pSurfaceDesc->Height; LPDIRECT3DVERTEXBUFFER9 lpVBTemp = NULL; HRESULT hr = pd3dDevice->CreateVertexBuffer(vb_size, 0, TypeRectVertex::fvf, D3DPOOL_MANAGED, &lpVBTemp, NULL); if(FAILED(hr)) return; LPVOID lpData = NULL; if(SUCCEEDED(lpVBTemp->Lock(0, vb_size, &lpData, 0))) { { TypeRectVertex * const pVertices = (TypeRectVertex*)m_VBInMemory; _ASSERTE(pVertices); for(int i = numvertices/2 - 1; i >= 0; i--) { TypeRectVertex V1; V1.x = i%2 == 0 ? 0 : fWidth; V1.y = 0; V1.w = 1; V1.z = (256.0 / (256.0 - 1.0)) * (1.0 - 1.0/(DOUBLE)(i+1)); int nColor = (INT)(V1.z * 256.0f); V1.color = D3DCOLOR_XRGB(nColor, nColor, nColor); TRACE2("X:%f, Z:%f\n",V1.x, V1.z); TypeRectVertex V2; V2.x = V1.x; V2.y = fHeight; V2.w = 1; V2.z = V1.z; V2.color = V1.color; TRACE2("X:%f, Z:%f\n",V2.x, V2.z); int nPlace = numvertices - 2 - i * 2; pVertices[nPlace] = V1; pVertices[nPlace+1] = V2; } memcpy_s(lpData, vb_size, pVertices, vb_size); } lpVBTemp->Unlock(); m_pVB = lpVBTemp; lpVBTemp = NULL; } SAFE_RELEASE(lpVBTemp); 3.2 State Setters: I use temporary struct which's constructor will record the states, and the destructor will apply the states. You should make sure these states are reverted to normal after the "Depth Drawing". You should understand these codes if you are familiar to those annoying D3DRS constants. ExtraStateApplying.m_pDevice = pd3dDevice; ExtraStateApplying.m_bZEnable = D3DZB_TRUE; ExtraStateApplying.m_bZWriteEnable = D3DZB_FALSE; ExtraStateApplying.m_Color = 0xffffffffff; ExtraStateApplying.tss_colorop = D3DTOP_SELECTARG1; ExtraStateApplying.tss_colorarg1 = D3DTA_DIFFUSE; ExtraStateApplying.dwCull = D3DCULL_NONE; StencilStateTemp.m_Enable = TRUE; StencilStateTemp.m_Fail = D3DSTENCILOP_KEEP; StencilStateTemp.m_ZFail = D3DSTENCILOP_ZERO; StencilStateTemp.m_Pass = D3DSTENCILOP_REPLACE; StencilStateTemp.m_Func = D3DCMP_GREATER; StencilStateTemp.m_Ref = 0x00000001; StencilStateTemp.m_Mask = 0xffffffff; StencilStateTemp.m_WriteMask = 0xffffffff; 3.3 Draw pd3dDevice->DrawPrimitive(D3DPT_TRIANGLESTRIP, 0, numquos*2);

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One way to get a depth texture with one pass is to simply render everything to a floating point surface, and always output the depth to the alpha channel.. do alpha testing with clip...Doesnt work with transparent polygons however.

I imagine you can fiddle with th numbers and pack it somewhere else also..

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I dont't think I am fiddling, man. I forgot to explain why I try to figure out such a tiresome method. As you say, you can simply get the depth by render the scene. You mean render every thing again with a PS outputs Z/W or use mul-render target, right?

What if there's no chance to render the scene again? That is the problem I am facing to. Believe me, I 've read lots of articles about shadows rendering.

I am now working on a complex program, which codes have been accumulated to an suffering height. It is extremly diffical for me to insert codes in those render functions, because most of them are written months ago by others without serious planned and most of them are nearly refraction incompatible. The best way to implement codes to launch a clean Z-buffer rendering, as you memsion, is to rewrite many codes to insert "RenderShadow" method in those model classes and every scene object classes. Moreover, some of our trees do not have a shader. That's why I try to implement such a bizarrerie method, when the boss is urging a realtime shadow.

I think few 3d programmers need to get z-buffer like this, if they have time to implement a depth rendering. I present this bizarrerie method just for exchanging ideas with you guys to figure out such adverse a situation.

At lease, my method has one advantage, isn't it? It only needs z-buffer :>

PS : who can tell me how to place an image on the thread?

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Original post by AlenWesker
I dont't think I am fiddling, man. I forgot to explain why I try to figure out such a tiresome method. As you say, you can simply get the depth by render the scene. You mean render every thing again with a PS outputs Z/W or use mul-render target, right?

What if there's no chance to render the scene again? That is the problem I am facing to. Believe me, I 've read lots of articles about shadows rendering.

I don't understand how your method solves the problem of not needing an extra pass. A normal shadow mapping algorithm works like this:

1. Render scene from the viewpoint of the light
2. Render the scene from the camera's viewpoint, comparing depth to the previous render

This inherently draws the scene twice.

If you're just talking about drawing step 1 twice, there's no need for this, since the scene itself need not be rendered. All you need is the Z buffer, and you can get that by rendering Z to a floating point texture.

Which is why I say that I don't understand what the exact problem is.

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Original post by AlenWeskerWhat if there's no chance to render the scene again?

Actually my method means that you only render your main scene just always render the depth to the alpha channel while rendering the colors...that's the point, as 'ET3D' says..

I was just considering the idea that you wanted a copy of the depth buffer only from the camera position, not for shadow mapping. But for shadow mapping you need to render the scene from the light's point of view, so there is nothing in the z-buffer stored already, so your method makes no sense at all.

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Hey, I think few guys have met my situation, so it's not surprising that it is so hard to explain. Normally, Shadow Map really needs render the scene twice. If you have fully control of your shaders and your models, just do as what you guys say. And if only the shadow is needed ,just render the shadow at the same time in the second pass with PS. We don't even need to render the depth into the alpha in this situation.

However, what if some objects are render with no shaders, and the codes have been messed up into great chaos? The best way is to sort them and add codes to do as what you suggests. I will do that some day, but not now, for the sake that the refration of this kind of mess is not a one-day job.

In order to just realize the shadow in a short time, I do like this:
1. Just let those messed-up codes do what they are supposed to do, even some objects are rendered without a shader.
2. Use the bizzare method I introduced above to get the depth.
3. Render the moving objects only to gain a shadow map.
4. Render the shadow using the depth map obtained in step 3,with every pixel being compared to the shadow map.

It does not save a pass, and what I mean is that I don't need to modify any previous codes to get the depth-----no need to modify shaders, and no need to dig a hole into those codes in chaos.

This bizzare method is temporary, however, it do provide a way to get the depth even you don't have shaders available, isn't it? I have no word to say if you insist I am fiddling.

Actually, I do not need to render my shadow like this right now, because I just implement a simply way to have soft shadow volumes yesterday. Let the depth go to hell.

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      As it was mentioned earlier, Diligent Engine follows next-gen APIs to configure the graphics/compute pipeline. One big Pipelines State Object (PSO) encompasses all required states (all shader stages, input layout description, depth stencil, rasterizer and blend state descriptions etc.). This approach maps directly to Direct3D12/Vulkan, but is also beneficial for older APIs as it eliminates pipeline misconfiguration errors. With many individual calls tweaking various GPU pipeline settings it is very easy to forget to set one of the states or assume the stage is already properly configured when in fact it is not. Using pipeline state object helps avoid these problems as all stages are configured at once.
      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 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 michaeldodis
      I've started building a small library, that can render pie menu GUI in legacy opengl, planning to add some traditional elements of course.
      It's interface is similar to something you'd see in IMGUI. It's written in C.
      Early version of the library
      I'd really love to hear anyone's thoughts on this, any suggestions on what features you'd want to see in a library like this? 
      Thanks in advance!
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