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Hey All, I have been creating a game engine using OpenGL for a while. It''s going fairly well. I have written a model loader, that loads a custom model format, I have shadows, and lighting, tons of other snazy fetures, and things are lookin great. I pull in wonderfull framerates.. whatever... I only say this cuz I''m proud of my little creation it being my first serious OpenGL endevour since I learned the API :D Anyway, one thing I don''t know how to do is any sort of model animation and I was hopeing some of you guys might point me in the right direction so that I may learn more about it. I have been toying around with various aproaches, I was considering saving my model in a series of "frames", that is, intermediate poses and cycling thrugh them during animation as you would a 2D sprite. Is this a simple, and fesable way of doing this? What is the best way to get your feet wet in what is obviously a very complicated part of 3D programming. Thank you very much.

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quote:

I was considering saving my model in a series of "frames", that is, intermediate poses and cycling thrugh them during animation as you would a 2D sprite. Is this a simple, and fesable way of doing this?



Certainly. This is the form that the Quake2 MD2 animations take. With this method (sometimes called vertex key-framing) you can use interpolation to smoothly transition from one frame to the next. Keyframes can be generated for, say, every 4 or 5 game display frames, then an interpolant between 0 and 1 is used to smoothly morph from the previous keyframe to the next keyframe. This eliminates the jerkiness that is inherent to key-framed animation (very visible with 2D sprite graphics, as interpolation is not feasible). To start with, this is a good animation route to take.

Another (more advanced) method is skeletal animation. In vertex-keyframing, memory usage can get out of hand for large models and long animations, as each keyframe requires a local copy of vertex data. In skeletal animation, a model is constructed and animated as a "skin" attached to a hierarchical frame or skeleton of "bones". Each vertex is transformed by a bone or a set of bones with weighting factors applied. Bones are represented as quaternions or some other form of rotation, a location relative to the parent hierarchy, and an endpoint to which any children in the chain are attached. With skeletal animation, instead of storing each vertex per key-frame, you can instead merely store the key-frame''s bone orientations, and maintin one reference copy of the mesh in it''s rest pose. Vertex transformations are performed on the fly, generated by transforming the reference copy of the mesh either into a temporary buffer or with the use of a vertex shader, and displaying the transformed geometry.

Skeletal animation offers additional benefits besides just decreased memory usage. With vertex key-framing, interpolation from one keyframe to the next is fastest accomplished with linear interpolation. However, in the case of mesh components that are hierarchical in nature and constrained, this can result in visual artifacts. Instead of, say, an arm rotating around an elbow joint, the mesh instead linearly morphs from one orientation to the next, causing shortening of the arm over the course of the movement. With keyframes that are spaced closely together this sort of shortening is not obvious. But in the case of rapidly moving animation with keyframes far apart, it becomes more apparent. Skeletal animation interpolates the orientation of the mesh sections, not their final positions, so that the arm is seen to rotate around the elbow joint rather than trying to morph "through" it.

With skeletal animation, it is also easier to compose different animation sequences together. For instance, it is easy to generate an animation sequence for walking, which modifies only the leg bones and perhaps the torso to a slight degree. Other animations might affect only the head, for head turning or gaze tracking, or the arms such as when a sword or other weapon is swung. With vertex key-framing, character multi-tasking in this manner is limited, but with skeletal animation these different animations which affect different parts of the body can easily be combined together, so that the character is seen to walk, turn his head, and swing his sword all at once.

Skeletal animation also allows the possibility of realistic physics, such as ragdoll physics and the like, wherein the members of a body are subject to real-time effects of impact, gravity, application of force, etc... Animations can then be generated that are not limited to what the designer creates in an animation package, but instead follow more (hopefully) realistic sequences created by the laws of the physics system applied.

As is to be expected, these latter methods can get to be extremely complex, and are not always suited to the application. Skeletal animation itself is far more complex, and thus more resource intensive, than simple vertex interpolation. Shaders and vertex programs can offload the grunt work of vertex transformation to the GPU, as long as programs are hardware supported. Realistic physics, too, add their complications, though some of these difficulties can be overcome by using pre-made physics packages such as OpenDE or Tokamak or others, which can handle many of the tricky calculations and allow you to concentrate on the big picture.

But not all games require realistic, powerful physics or modelling simulations. If you are willing to constrain animation to pre-packaged movements, ala traditional 2D animation, vertex key-framing can be more than sufficient for your needs. Even in fantastically modelled simulations, simple vertex morphing can have its place, in animations not so well suited to hierarchical skeletal arrangement.


Golem
Blender--The Gimp--Python--Lua--SDL
Nethack--Crawl--ADOM--Angband--Dungeondweller

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VertexNormal,

Thanks allot for that excellent, well thought out, and articulate reply. Because of your thurough explanation, I realize that Linear interpolation sounds like the way I want to go.

My game is a turn-based RPG, so it dosn''t need fancy physycs or anything like that. My models are also not incredibly complex either, so I don''t think the memory usage will be too over the top.

I found some tutorials using .md2 models over at DigiBen. It has a good explanation of how it''s done in the header file. Though my game dosn''t use md2s, rather a much simpler format devised by myself, the tutorial still gives a good understanding to hack thugh it for my personal needs.

However, if anyone has any advice, links, or relevant suggestions concerning Liniar Interpolation please, by all means, let me know.

Thank you very much.

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Linear interpolation is really very simple.

Say you have two points: PointA and PointB. Each is a vertex in a mesh (x,y, and z components). The standard linear interp. function is:

c = a + t*(b-a)

Where t is a number in the range of [ 0,1].

So, if PointA=(5, 2, 12) and PointB=(18, 4, 20) then we can find any location in between using the above formula. For instance, at t=0.5 (the exact midpoint between the two points):

PointC = PointA + t*(PointB-PointA);

PointC.x = 5 + 0.5*(18-5) = 11.5
PointC.y = 2 + 0.5*(4-2) = 3
PointC.z = 12 + 0.5*(20-12) = 16

So, PointC at t=0.5 is equal to (11.5, 3, 16)

Now, each keyframe of the animation is going to consist of an array or list of vertices for the entire mesh for that frame. An animating object needs to keep track of two keyframes: Previous and Next. It will also track a current value for t, which will increase in small increments each time the game logic updates. Each object will also track a Previous and Next Location as well.

Now, when you render the scene you need to generate a current "snapshot" of the object as it stands at that point in time, using it''s t value. You apply the linear interpolation equation above to the PreviousLocation and NextLocation to generate an intermediate location-- the object''s location at that point in time. By the same token, you apply the linear interpolation equation to each vertex in PreviousFrame and NextFrame, to generate the in-between frame for time=t.

t can be updated and manipulated to increase in increments as fine as you need or as the frame-rate will allow. Each time it is incremented, you check to see if it goes greater than 1. If so, then you need to wrap it back around by subtracting one, then advance your animation and positional data. PreviousFrame is set to NextFrame, and a new NextFrame is generated to continue the animation. PreviousLocation is set to NextLocation, and a new location is generated for NextLocation. And so on, and so on.

The way I do it is I space all of my key-frames a constant number of frames apart (say, 4 logic frames per keyframe). This way, each time the game logic updates, I can advance t by 0.25 (1 / UpdateRate, or 1/4 for UpdateRate=4) to generate the in between frames. So, in sequence the render will draw frames at t=0 (or, PreviousFrame), t=0.25, t=0.5, t=0.75, t=1.0 (or, NextFrame). At t=1.0, I advance a frame and wrap t back around to 0 to start again.

There are other methods for interpolation besides linear. Linear interpolation, as the name implies, can determine arbitrary points along a straight line between point a and point b-- thus the flattening or shortening of rotating arms and the like. Other forms of interpolation can approximate a curve between points rather than a straight line, thus possibly resulting in smoother, more realistic animation with less flattening and distortion.

Cosine interpolation is calculated thus:

float ft = t * 3.1415927f;
float f = (1 - cos(ft)) * 0.5f;
return a*(1-f) + b*f;


This form of interpolation connects two points with an approximation of a curve. I say approximation, because that is all it is. A true curve takes into account more information to generate a smoother path. Such a true curve might be cubic interpolation:

Given: Points a, b, c, d as control points (keyframes) on the curve

Point e = (d - c) - (a - b);
Point f = (a - b) - e;
Point g = c - a;
Point h = b;

return e*t*t*t + f*t*t + g*t + h;


This gives a much smoother, more continuous curve connecting the points, but at the cost of having to remember 4 points: two Previous and two Next points. This may not be suitable for animation which can change state between one frame and the next, so it probably is not appropriate for vertex keyframing.

But, like I said before, if you generate your key-frames close enough together, any distortion from linear interpolation can be minimized so as to be nearly undetectable. More complex interpolation requires more processing time, which can have an effect on framerate when you need to do several hundred thousand interpolations per frame for a lot of objects.




If you structure your game loop correctly, it is possible to not only interpolate from one key frame to the next by frames (ie, advancing t by 0.25 each time, or whatever); it is also possible to go even finer, interpolating between even these intermediate frames to a degree allowed by the video frame rate.

For example, say I am running my simulation logic updating at 25 frames per second, advancing the game logic one step every 40 ms. That means that every 40 ms, t for all object animations advances by 0.25 (assuming, of course, that is the update interval I chose). 25 fps is great for complicated logic, as it gives a decent CPU plenty of time to calculate a frame and do all of the AI, but the drawback is it locks the video frame rate to 25 fps as well. t only increments every 40ms, so in the meantime we are just drawing the same exact scene over and over until t increments again. Our video card might be capable of 900 fps, but the game locks it to 25 by forcing it to redraw the same scene over and over for most of the time.

What we want to be able to do instead is interpolate from Previous keyframe to Next keyframe to generate the current frame, then advance the animation even further based on how far into the next frame we are. It''s a little complicated, so I won''t describe it in depth here. The implementation I use is pretty much exactly as Javier Arevalo details in his Tip of the Day at Flipcode.com. In his algorithm, he performs game logic updates at a fixed time step, and in the meantime calculates an interpolation factor (PercentWithinTick) to calculate how far along we are between this tick and the next. All rendering functions can use this factor to further interpolate animation and smooth things out.

Consider the case where we advance t for a model by 0.25 each tick. Now, say at a given point in time the loop calculates PercentWithinTick to be 0.5, meaning we are halfway to the next update tick. We can apply this PercentWithinTick to the update rate (PercentWithinTick * 0.25) and add this to an object''s current t value to account for how far into the next tick we are. This has the effect of smoothing out our 25 fps video framerate to take advantage of all the fps the card can pile on. 25fps jerks or steps in animation are interpolated and smoothed. It works very nicely, but can be a little difficult to understand at first.

Anyway, I hope this helps and I hope my wandering all over the place hasn''t confused you. Good luck and have fun.



Golem
Blender--The Gimp--Python--Lua--SDL
Nethack--Crawl--ADOM--Angband--Dungeondweller

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VN,

I just had to reply with a tremendous thank you!

Your fantastic post totaly gor my model animated and walking around my 3D world!

Thank you so much.

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Guest Anonymous Poster
Superb post, Vertex Normal. Very informative.

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      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.
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