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    • By kanageddaamen
      Hello all,
      I am currently working on a game engine for use with my game development that I would like to be as flexible as possible.  As such the exact requirements for how things should work can't be nailed down to a specific implementation and I am looking for, at least now, a default good average case scenario design.
      Here is what I have implemented:
      Deferred rendering using OpenGL Arbitrary number of lights and shadow mapping Each rendered object, as defined by a set of geometry, textures, animation data, and a model matrix is rendered with its own draw call Skeletal animations implemented on the GPU.   Model matrix transformation implemented on the GPU Frustum and octree culling for optimization Here are my questions and concerns:
      Doing the skeletal animation on the GPU, currently, requires doing the skinning for each object multiple times per frame: once for the initial geometry rendering and once for the shadow map rendering for each light for which it is not culled.  This seems very inefficient.  Is there a way to do skeletal animation on the GPU only once across these render calls? Without doing the model matrix transformation on the CPU, I fail to see how I can easily batch objects with the same textures and shaders in a single draw call without passing a ton of matrix data to the GPU (an array of model matrices then an index for each vertex into that array for transformation purposes?) If I do the matrix transformations on the CPU, It seems I can't really do the skinning on the GPU as the pre-transformed vertexes will wreck havoc with the calculations, so this seems not viable unless I am missing something Overall it seems like simplest solution is to just do all of the vertex manipulation on the CPU and pass the pre-transformed data to the GPU, using vertex shaders that do basically nothing.  This doesn't seem the most efficient use of the graphics hardware, but could potentially reduce the number of draw calls needed.

      Really, I am looking for some advice on how to proceed with this, how something like this is typically handled.  Are the multiple draw calls and skinning calculations not a huge deal?  I would LIKE to save as much of the CPU's time per frame so it can be tasked with other things, as to keep CPU resources open to the implementation of the engine.  However, that becomes a moot point if the GPU becomes a bottleneck.
    • By DiligentDev
      I would like to introduce Diligent Engine, a project that I've been recently working on. Diligent Engine is a light-weight cross-platform abstraction layer between the application and the platform-specific graphics API. Its main goal is to take advantages of the next-generation APIs such as Direct3D12 and Vulkan, but at the same time provide support for older platforms via Direct3D11, OpenGL and OpenGLES. Diligent Engine exposes common front-end for all supported platforms and provides interoperability with underlying native API. Shader source code converter allows shaders authored in HLSL to be translated to GLSL and used on all platforms. Diligent Engine supports integration with Unity and is designed to be used as a graphics subsystem in a standalone game engine, Unity native plugin or any other 3D application. It is distributed under Apache 2.0 license and is free to use. Full source code is available for download on GitHub.
      True cross-platform Exact same client code for all supported platforms and rendering backends No #if defined(_WIN32) ... #elif defined(LINUX) ... #elif defined(ANDROID) ... No #if defined(D3D11) ... #elif defined(D3D12) ... #elif defined(OPENGL) ... Exact same HLSL shaders run on all platforms and all backends Modular design Components are clearly separated logically and physically and can be used as needed Only take what you need for your project (do not want to keep samples and tutorials in your codebase? Simply remove Samples submodule. Only need core functionality? Use only Core submodule) No 15000 lines-of-code files Clear object-based interface No global states Key graphics features: Automatic shader resource binding designed to leverage the next-generation rendering APIs Multithreaded command buffer generation 50,000 draw calls at 300 fps with D3D12 backend Descriptor, memory and resource state management Modern c++ features to make code fast and reliable The following platforms and low-level APIs are currently supported:
      Windows Desktop: Direct3D11, Direct3D12, OpenGL Universal Windows: Direct3D11, Direct3D12 Linux: OpenGL Android: OpenGLES MacOS: OpenGL iOS: OpenGLES API Basics
      The engine can perform initialization of the API or attach to already existing D3D11/D3D12 device or OpenGL/GLES context. For instance, the following code shows how the engine can be initialized in D3D12 mode:
      #include "RenderDeviceFactoryD3D12.h" using namespace Diligent; // ...  GetEngineFactoryD3D12Type GetEngineFactoryD3D12 = nullptr; // Load the dll and import GetEngineFactoryD3D12() function LoadGraphicsEngineD3D12(GetEngineFactoryD3D12); auto *pFactoryD3D11 = GetEngineFactoryD3D12(); EngineD3D12Attribs EngD3D12Attribs; EngD3D12Attribs.CPUDescriptorHeapAllocationSize[0] = 1024; EngD3D12Attribs.CPUDescriptorHeapAllocationSize[1] = 32; EngD3D12Attribs.CPUDescriptorHeapAllocationSize[2] = 16; EngD3D12Attribs.CPUDescriptorHeapAllocationSize[3] = 16; EngD3D12Attribs.NumCommandsToFlushCmdList = 64; RefCntAutoPtr<IRenderDevice> pRenderDevice; RefCntAutoPtr<IDeviceContext> pImmediateContext; SwapChainDesc SwapChainDesc; RefCntAutoPtr<ISwapChain> pSwapChain; pFactoryD3D11->CreateDeviceAndContextsD3D12( EngD3D12Attribs, &pRenderDevice, &pImmediateContext, 0 ); pFactoryD3D11->CreateSwapChainD3D12( pRenderDevice, pImmediateContext, SwapChainDesc, hWnd, &pSwapChain ); Creating Resources
      Device resources are created by the render device. The two main resource types are buffers, which represent linear memory, and textures, which use memory layouts optimized for fast filtering. To create a buffer, you need to populate BufferDesc structure and call IRenderDevice::CreateBuffer(). The following code creates a uniform (constant) buffer:
      BufferDesc BuffDesc; BufferDesc.Name = "Uniform buffer"; BuffDesc.BindFlags = BIND_UNIFORM_BUFFER; BuffDesc.Usage = USAGE_DYNAMIC; BuffDesc.uiSizeInBytes = sizeof(ShaderConstants); BuffDesc.CPUAccessFlags = CPU_ACCESS_WRITE; m_pDevice->CreateBuffer( BuffDesc, BufferData(), &m_pConstantBuffer ); Similar, to create a texture, populate TextureDesc structure and call IRenderDevice::CreateTexture() as in the following example:
      TextureDesc TexDesc; TexDesc.Name = "My texture 2D"; TexDesc.Type = TEXTURE_TYPE_2D; TexDesc.Width = 1024; TexDesc.Height = 1024; TexDesc.Format = TEX_FORMAT_RGBA8_UNORM; TexDesc.Usage = USAGE_DEFAULT; TexDesc.BindFlags = BIND_SHADER_RESOURCE | BIND_RENDER_TARGET | BIND_UNORDERED_ACCESS; TexDesc.Name = "Sample 2D Texture"; m_pRenderDevice->CreateTexture( TexDesc, TextureData(), &m_pTestTex ); Initializing Pipeline State
      Diligent Engine follows Direct3D12 style 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.)
      Creating Shaders
      To create a shader, populate ShaderCreationAttribs structure. An important member is ShaderCreationAttribs::SourceLanguage. The following are valid values for this member:
      SHADER_SOURCE_LANGUAGE_DEFAULT  - The shader source format matches the underlying graphics API: HLSL for D3D11 or D3D12 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. See shader converter for details. SHADER_SOURCE_LANGUAGE_GLSL  - The shader source is in GLSL. There is currently no GLSL to HLSL converter. To allow grouping of resources based on the frequency of expected change, Diligent Engine introduces classification of shader variables:
      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. This post describes the resource binding model in Diligent Engine.
      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
      To create a pipeline state object, define instance of PipelineStateDesc structure. The structure defines the pipeline specifics such as if the pipeline is a compute pipeline, number and format of render targets as well as depth-stencil format:
      // This is a graphics pipeline PSODesc.IsComputePipeline = false; PSODesc.GraphicsPipeline.NumRenderTargets = 1; PSODesc.GraphicsPipeline.RTVFormats[0] = TEX_FORMAT_RGBA8_UNORM_SRGB; PSODesc.GraphicsPipeline.DSVFormat = TEX_FORMAT_D32_FLOAT; The structure also defines depth-stencil, rasterizer, blend state, input layout and other parameters. For instance, rasterizer state can be defined as in the code snippet below:
      // Init rasterizer state RasterizerStateDesc &RasterizerDesc = PSODesc.GraphicsPipeline.RasterizerDesc; RasterizerDesc.FillMode = FILL_MODE_SOLID; RasterizerDesc.CullMode = CULL_MODE_NONE; RasterizerDesc.FrontCounterClockwise = True; RasterizerDesc.ScissorEnable = True; //RSDesc.MultisampleEnable = false; // do not allow msaa (fonts would be degraded) RasterizerDesc.AntialiasedLineEnable = False; When all fields are populated, call IRenderDevice::CreatePipelineState() to create the PSO:
      m_pDev->CreatePipelineState(PSODesc, &m_pPSO); Binding Shader Resources
      Shader resource binding in Diligent Engine is based on grouping variables in 3 different groups (static, mutable and dynamic). Static variables 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. They are bound directly to the shader object:
      PixelShader->GetShaderVariable( "g_tex2DShadowMap" )->Set( pShadowMapSRV ); Mutable and dynamic variables are bound via a new object called Shader Resource Binding (SRB), which is created by the pipeline state:
      m_pPSO->CreateShaderResourceBinding(&m_pSRB); Dynamic and mutable resources are then bound through SRB object:
      m_pSRB->GetVariable(SHADER_TYPE_VERTEX, "tex2DDiffuse")->Set(pDiffuseTexSRV); m_pSRB->GetVariable(SHADER_TYPE_VERTEX, "cbRandomAttribs")->Set(pRandomAttrsCB); The difference between mutable and dynamic resources is that mutable ones can only be set once for every instance of a shader resource binding. Dynamic resources can be set multiple times. It is important to properly set the variable type as this may affect performance. Static variables are generally most efficient, followed by mutable. Dynamic variables are most expensive from performance point of view. This post explains shader resource binding in more details.
      Setting the Pipeline State and Invoking Draw Command
      Before any draw command can be invoked, all required vertex and index buffers as well as the pipeline state should be bound to the device context:
      // Clear render target const float zero[4] = {0, 0, 0, 0}; m_pContext->ClearRenderTarget(nullptr, zero); // 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); m_pContext->SetPipelineState(m_pPSO); Also, all shader resources must be committed to the device context:
      m_pContext->CommitShaderResources(m_pSRB, COMMIT_SHADER_RESOURCES_FLAG_TRANSITION_RESOURCES); When all required states and resources are bound, IDeviceContext::Draw() can be used to execute draw command or IDeviceContext::DispatchCompute() can be used to execute compute command. Note that for a draw command, graphics pipeline must be bound, and for dispatch command, compute pipeline must be bound. Draw() 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); Tutorials and Samples
      The GitHub repository contains a number of tutorials and sample applications that demonstrate the API usage.
      Tutorial 01 - Hello Triangle This tutorial shows how to render a simple triangle using Diligent Engine API.   Tutorial 02 - Cube This tutorial demonstrates how to render an actual 3D object, a cube. It shows how to load shaders from files, create and use vertex, index and uniform buffers.   Tutorial 03 - Texturing This tutorial demonstrates how to apply a texture to a 3D object. It shows how to load a texture from file, create shader resource binding object and how to sample a texture in the shader.   Tutorial 04 - Instancing This tutorial demonstrates how to use instancing to render multiple copies of one object using unique transformation matrix for every copy.   Tutorial 05 - Texture Array This tutorial demonstrates how to combine instancing with texture arrays to use unique texture for every instance.   Tutorial 06 - Multithreading This tutorial shows how to generate command lists in parallel from multiple threads.   Tutorial 07 - Geometry Shader This tutorial shows how to use geometry shader to render smooth wireframe.   Tutorial 08 - Tessellation This tutorial shows how to use hardware tessellation to implement simple adaptive terrain rendering algorithm.   Tutorial_09 - Quads This tutorial shows how to render multiple 2D quads, frequently swithcing textures and blend modes.
      AntTweakBar sample demonstrates how to use AntTweakBar library to create simple user interface.

      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 textures, using compute shaders and unordered access views, etc. 

      The repository includes Asteroids performance benchmark based on this demo developed by Intel. It renders 50,000 unique textured asteroids and lets compare performance of D3D11 and D3D12 implementations. Every asteroid is a combination of one of 1000 unique meshes and one of 10 unique textures. 

      Integration with Unity
      Diligent Engine supports integration with Unity through Unity low-level native plugin interface. The engine relies on Native API Interoperability to attach to the graphics API initialized by Unity. After Diligent Engine device and context are created, they can be used us usual to create resources and issue rendering commands. GhostCubePlugin shows an example how Diligent Engine can be used to render a ghost cube only visible as a reflection in a mirror.

    • By Yxjmir
      I'm trying to load data from a .gltf file into a struct to use to load a .bin file. I don't think there is a problem with how the vertex positions are loaded, but with the indices. This is what I get when drawing with glDrawArrays(GL_LINES, ...):

      Also, using glDrawElements gives a similar result. Since it looks like its drawing triangles using the wrong vertices for each face, I'm assuming it needs an index buffer/element buffer. (I'm not sure why there is a line going through part of it, it doesn't look like it belongs to a side, re-exported it without texture coordinates checked, and its not there)
      I'm using jsoncpp to load the GLTF file, its format is based on JSON. Here is the gltf struct I'm using, and how I parse the file:
      #define GLTF_TARGET_ARRAY_BUFFER (34962) #define GLTF_TARGET_ELEMENT_ARRAY_BUFFER (34963) #define GLTF_COMPONENT_TYPE_BYTE (5120) #define GLTF_COMPONENT_TYPE_UNSIGNED_BYTE (5121) #define GLTF_COMPONENT_TYPE_SHORT (5122) #define GLTF_COMPONENT_TYPE_UNSIGNED_SHORT (5123) #define GLTF_COMPONENT_TYPE_INT (5124) #define GLTF_COMPONENT_TYPE_UNSIGNED_INT (5125) #define GLTF_COMPONENT_TYPE_FLOAT (5126) #define GLTF_COMPONENT_TYPE_DOUBLE (5127) #define GLTF_PARAMETER_TYPE_BYTE (5120) #define GLTF_PARAMETER_TYPE_UNSIGNED_BYTE (5121) #define GLTF_PARAMETER_TYPE_SHORT (5122) #define GLTF_PARAMETER_TYPE_UNSIGNED_SHORT (5123) #define GLTF_PARAMETER_TYPE_INT (5124) #define GLTF_PARAMETER_TYPE_UNSIGNED_INT (5125) #define GLTF_PARAMETER_TYPE_FLOAT (5126) #define GLTF_PARAMETER_TYPE_FLOAT_VEC2 (35664) #define GLTF_PARAMETER_TYPE_FLOAT_VEC3 (35665) #define GLTF_PARAMETER_TYPE_FLOAT_VEC4 (35666) struct GLTF { struct Accessor { USHORT bufferView; USHORT componentType; UINT count; vector<INT> max; vector<INT> min; string type; }; vector<Accessor> m_accessors; struct Asset { string copyright; string generator; string version; }m_asset; struct BufferView { UINT buffer; UINT byteLength; UINT byteOffset; UINT target; }; vector<BufferView> m_bufferViews; struct Buffer { UINT byteLength; string uri; }; vector<Buffer> m_buffers; vector<string> m_Images; struct Material { string name; string alphaMode; Vec4 baseColorFactor; UINT baseColorTexture; UINT normalTexture; float metallicFactor; }; vector<Material> m_materials; struct Meshes { string name; struct Primitive { vector<UINT> attributes_indices; UINT indices; UINT material; }; vector<Primitive> primitives; }; vector<Meshes> m_meshes; struct Nodes { int mesh; string name; Vec3 translation; }; vector<Nodes> m_nodes; struct Scenes { UINT index; string name; vector<UINT> nodes; }; vector<Scenes> m_scenes; vector<UINT> samplers; struct Textures { UINT sampler; UINT source; }; vector<Textures> m_textures; map<UINT, string> attributes_map; map<UINT, string> textures_map; }; GLTF m_gltf; // This is actually in the Mesh class bool Mesh::Load(string sFilename) { string sFileAsString; stringstream sStream; ifstream fin(sFilename); sStream << fin.rdbuf(); fin.close(); sFileAsString = sStream.str(); Json::Reader r; Json::Value root; if (!r.parse(sFileAsString, root)) { string errors = r.getFormatedErrorMessages(); if (errors != "") { // TODO: Log errors return false; } } if (root.isNull()) return false; Json::Value object; Json::Value value; // Load Accessors array, these are referenced by attributes with their index value object = root.get("accessors", Json::Value()); // store object with key "accessors", if not found it will default to Json::Value() if (!object.isNull()) { for (Json::ValueIterator it = object.begin(); it != object.end(); it++) { GLTF::Accessor accessor; value = (*it).get("bufferView", Json::Value()); if (!value.isNull()) accessor.bufferView = value.asUINT(); else return false; value = (*it).get("componentType", Json::Value()); if (!value.isNull()) accessor.componentType = value.asUINT(); else return false; value = (*it).get("count", Json::Value()); if (!value.isNull()) accessor.count = value.asUINT(); else return false; value = (*it).get("type", Json::Value()); if (!value.isNull()) accessor.type = value.asString(); else return false; m_gltf.accessors.push_back(accessor); } } else return false; object = root.get("bufferViews", Json::Value()); if(!object.isNull()) { for (Json::ValueIterator it = object.begin(); it != object.end(); it++) { GLTF::BufferView bufferView; value = (*it).get("buffer", Json::Value()); if(!value.isNull()) bufferView.buffer = value.asUInt(); else return false; value = (*it).get("byteLength", Json::Value()); if(!value.isNull()) bufferView.byteLength = value.asUInt(); else return false; value = (*it).get("byteOffset", Json::Value()); if(!value.isNull()) bufferView.byteOffset = value.asUInt(); else return false; value = (*it).get("target", Json::Value()); if(!value.isNull()) bufferView.target = value.asUInt(); else return false; m_gltf.m_bufferViews.push_back(bufferView); } } else return false; object = root.get("buffers", Json::Value()); if(!object.isNull()) { for (Json::ValueIterator it = object.begin(); it != object.end(); it++) { GLTF::Buffer buffer; value = (*it).get("byteLength", Json::Value()); if(!value.isNull()) buffer.byteLength = value.asUInt(); else return false; // Store the filename of the .bin file value = (*it).get("uri", Json::Value()); if(!value.isNull()) buffer.uri = value.asString(); else return false; } } else return false; object = root.get("meshes", Json::Value()); if(!object.isNull()) { for(Json::ValueIterator it = object.begin(); it != object.end(); it++) { GLTF::Meshes mesh; value = (*it).get("primitives", Json::Value()); for(Json::ValueIterator value_it = value.begin(); value_it != value.end(); value_it++) { GLTF::Meshes::Primitive primitive; Json::Value attributes; attributes = (*value_it).get("attributes", Json::Value()); vector<string> memberNames = attributes.getMemberNames(); for(size_t i = 0; i < memberNames.size(); i++) { Json::Value member; member = attributes.get(memeberNames[i], Json::Value()); if(!member.isNull()) { primitive.attributes_indices.push_back(member.asUInt()); m_gltf.attributes_map[member.asUInt()] = memberNames[i]; // Each of these referes to an accessor by indice, so each indice should be unique, and they are when loading a cube } else return false; } // Indice of the accessor used for indices Json::Value indices; indices = (*value_it).get("indices", Json::Value()); primitive.indices = indices.asUInt(); mesh.primitives.push_back(primitive); } m_gltf.m_meshes.push_back(mesh); } } vector<float> vertexData; vector<USHORT> indiceData; int vertexBufferSizeTotal = 0; int elementBufferSizeTotal = 0; GLTF::Meshes mesh = m_gltf.m_meshes[0]; vector<GLTF::Meshes::Primitive> primitives = mesh.primitives; // trying to make the code easier to read for (size_t p = 0; p < primitive.size(); p++) { vector<UINT> attributes = primitives[p].attributes_indices; for(size_t a = 0; a < attributes.size(); a++) { GLTF::Accessor accessor = m_gltf.m_accessors[attributes[a]]; GLTF::BufferView bufferView = m_gltf.m_bufferViews[accessor.bufferView]; UINT target = bufferView.target; if(target == GLTF_TARGET_ARRAY_BUFFER) vertexBufferSizeTotal += bufferView.byteLength; } UINT indice = primitives[p].indices; GLTF::BufferView bufferView = m_gltf.m_bufferViews[indice]; UINT target = bufferView.target; if(target == GLTF_TARGET_ELEMENT_ARRAY_BUFFER) elementBufferSizeTotal += bufferView.byteLength; } // These have already been generated glBindVertexArray(g_pGame->m_VAO); glBindBuffer(GL_ARRAY_BUFFER, g_pGame->m_VBO); glBufferData(GL_ARRAY_BUFFER, vertexBufferSizeTotal, nullptr, GL_STATIC_DRAW); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, g_pGame->m_EBO); glBufferData(GL_ELEMENT_ARRAY_BUFFER, elementBufferSizeTotal, nullptr, GL_STATIC_DRAW); int offset = 0; int offset_indice = 0; for (size_t p = 0; p < primitive.size(); p++) { vector<UINT> attributes = primitives[p].attributes_indices; int pos = sFilename.find_last_of('\\') + 1; string sFolder = sFilename.substr(0, pos); for (size_t a = 0; a < attributes.size(); a++) { LoadBufferView(sFolder, attributes[a], data, offset); } UINT indice = primitives[p].indices; GLTF::BufferView bufferView_indice = m_gltf.m_bufferViews[indice]; UINT target_indice = bufferView_indice.target; bool result = LoadBufferView(sFolder, indice, data, offset_indice); if(!result) return false; } return true; } bool Mesh::LoadBufferView(string sFolder, UINT a, vector<float> &vertexData, vector<float> &indiceData, int &offset_indice) { ifstream fin; GLTF::Accessor accessor = m_gltf.m_accessors[a]; GLTF::BufferView bufferView = m_gltf.m_bufferViews[accessor.bufferView]; GLTF::Buffer buffer = m_gltf.m_buffers[bufferView.buffer]; const size_t count = accessor.count; UINT target = bufferView.target; int elementSize; int componentSize; int numComponents; string sFilename_bin = sFolder + buffer.uri; fin.open(sFilename_bin, ios::binary); if (fin.fail()) { return false; } fin.seekg(bufferView.byteOffset, ios::beg); switch (accessor.componentType) { case GLTF_COMPONENT_TYPE_BYTE: componentSize = sizeof(GLbyte); break; case GLTF_COMPONENT_TYPE_UNSIGNED_BYTE: componentSize = sizeof(GLubyte); break; case GLTF_COMPONENT_TYPE_SHORT: componentSize = sizeof(GLshort); break; case GLTF_COMPONENT_TYPE_UNSIGNED_SHORT: componentSize = sizeof(GLushort); break; case GLTF_COMPONENT_TYPE_INT: componentSize = sizeof(GLint); break; case GLTF_COMPONENT_TYPE_UNSIGNED_INT: componentSize = sizeof(GLuint); break; case GLTF_COMPONENT_TYPE_FLOAT: componentSize = sizeof(GLfloat); break; case GLTF_COMPONENT_TYPE_DOUBLE: componentSize = sizeof(GLfloat); break; default: componentSize = 0; break; } if (accessor.type == "SCALAR") numComponents = 1; else if (accessor.type == "VEC2") numComponents = 2; else if (accessor.type == "VEC3") numComponents = 3; else if (accessor.type == "VEC4") numComponents = 4; else if (accessor.type == "MAT2") numComponents = 4; else if (accessor.type == "MAT3") numComponents = 9; else if (accessor.type == "MAT4") numComponents = 16; else return false; vector<float> fSubdata; // I'm pretty sure this is one of the problems, or related to it. If I use vector<USHORT> only half of the vector if filled, if I use GLubyte, the entire vector is filled, but the data might not be right vector<GLubyte> nSubdata; elementSize = (componentSize) * (numComponents); // Only fill the vector I'm using if (accessor.type == "SCALAR") { nSubdata.resize(count * numComponents); fin.read(reinterpret_cast<char*>(&nSubdata[0]), count/* * elementSize*/); // I commented this out since I'm not sure which size the .bin is storing the indice values, and I kept getting runtime errors, no matter what type I used for nSubdata } else { fSubdata.resize(count * numComponents); fin.read(reinterpret_cast<char*>(&fSubdata[0]), count * elementSize); } switch (target) { case GLTF_TARGET_ARRAY_BUFFER: { vertexData.insert(vertexData.end(), fSubdata.begin(), fSubdata.end()); glBindBuffer(GL_ARRAY_BUFFER, g_pGame->m_VBO); glBufferSubData(GL_ARRAY_BUFFER, offset, fSubdata.size() * componentSize, &fSubdata[0]); int attribute_index = 0; // I'm only loading vertex positions, the only attribute stored in the files for now glEnableVertexAttribArray(attribute_index); glVertexAttribPointer(0, numComponents, GL_FLOAT, GL_FALSE, componentSize * numComponents, (void*)(offset)); }break; case GLTF_TARGET_ELEMENT_ARRAY_BUFFER: { indiceData.insert(indiceData.end(), nSubdata.begin(), nSubdata.end()); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, g_pGame->m_EBO); // This is another area where I'm not sure of the correct values, but if componentSize is the correct size for the type being used it should be correct glBufferSubData is expecting the size in bytes, right? glBufferSubData(GL_ELEMENT_ARRAY_BUFFER, offset, nSubdata.size() * componentSize, &nSubdata[0]); }break; default: return false; } if (accessor.type == "SCALAR") offset += nSubdata.size() * componentSize; else offset += fSubdata.size() * componentSize; fin.close(); return true; } these are the draw calls, I only use one at a time, but neither is currently display properly, g_pGame->m_indices is the same as indiceData vector, and vertexCount contains the correct vertex count, but I forgot to copy the lines of code containing where I set them, which is at the end of Mesh::Load(), I double checked the values to make sure.
      glDrawElements(GL_LINES, g_pGame->m_indices.size(), GL_UNSIGNED_BYTE, (void*)0); // Only shows with GL_UNSIGNED_BYTE
      glDrawArrays(GL_LINES, 0, g_pGame->m_vertexCount);
      So, I'm asking what type should I use for the indices? it doesn't seem to be unsigned short, which is what I selected with the Khronos Group Exporter for blender. Also, am I reading part or all of the .bin file wrong?
    • By ritzmax72
      That means how do I use base DirectX or OpenGL api's to make a physics based destruction simulation? 
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    • By jsquare89
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      i’ve been stuck on this for far too long. any help would be much appreciated
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OpenGL Annoying jerkiness on OpenGL

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Hi I've wrote a fairly basic OpenGL program in C++. It has standard Windows code and also makes use of DirectInput and the performance counter to control the speed of animation. I'm planning to write a 2D platform game. At the moment I have 1 textured polygon (quad) which bounces around the edges of the screen. I'm not happy though cos the sprite movement is just not acceptable at all. Every 3 to 4 seconds it seems to jump a few pixels. The movement of the polygon should be smooth around the screen but it isn't. Surely my 700Mhz celeron is up to the task of moving a single polygon around a screen?? Could it maybe be my firewall software getting in the way? I've got no idea. Steve

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Could it be your code? Can't tell. - How are you moving it your polygon? What kind of graphics card do you have? Etc...

Specifically I am interested in your performance counter to "control the speed of animation."

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Hello, reaktor,

I'm not entirely sure what the problem is. But try turning on Vsync manually in your graphics control panel and see if that solves the problem. What is your FPS when running the program? Is the movement time-based or frame-based?
If it is time-based, it could be that some frames are skipped for the quad to reach it's destination in time.

Just some quick thoughts though. Please explain the problem a bit more in-depth if you want a better solution.


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It's probably some random background task running in Windows. Try closing background applications and services and you should see your FPS come back :-)

Just a quick note - it can sometimes be useful to use a low level tool to diagnose what software exactly is eating up your CPU time. Task manager can help find CPU hogs, but services are slightly trickier. Often disk access is the main culprit for slow speed and a tool like Filemon can be very useful to help diagnose problem software.

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Original post by reaktor

I've wrote a fairly basic OpenGL program in C++. It has standard Windows code and also makes use of DirectInput and the performance counter to control the speed of animation. I'm planning to write a 2D platform game.

At the moment I have 1 textured polygon (quad) which bounces around the edges of the screen. I'm not happy though cos the sprite movement is just not acceptable at all. Every 3 to 4 seconds it seems to jump a few pixels. The movement of the polygon should be smooth around the screen but it isn't. Surely my 700Mhz celeron is up to the task of moving a single polygon around a screen??

Could it maybe be my firewall software getting in the way? I've got no idea.


I had the same problem where the animations and entities in the game would jerk a bit sometimes and this would occur randomly. I fought with it for days and weeks eventually it turned out that the effect would go away when I shutdown the antivirus scanner (AVG) and OpenOffice quickstart from the taskbar in Windows. It could very well be your firewall or some other software running in the background.

Hope that helps.

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Thanks for the replies. I've just tried outputting my framerate to the screen and its a bit erratic to say the least. I get between 60 to 180 fps. Its constantly changing. I guess this is due to the graphics card not using vsync.

I'm borrowing this computer from a mate and it isn't particularly great. The graphics card is an on-board thingy and doesn't seem to have any vsync settings in the control panel so I can't lock the framerate. Plus the mouse is knackered so I am forced to use the keyboard for navigating around windows. Not much fun!

As someone mentioned, the jerking does seem to occur during hard drive access so maybe it is one of the programs running in the background. Its gona be pretty annoying though if I have to turn off my virus checker/firewall everytime I want to test my application.

Strange that other programs (such as emulators) seem to run fine with no jerking graphics.

I remember reading in the OpenGL superbible that you can get around Windows background tasks by using threading in your program. Hs anyone tried this? It looked a little complex so I ignored it. Maybe I should take another look.


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Ok, I've had a bit of a play and...

...It was the firewall. Seemed to be knocking a few fps off the framerate every few seconds which causes the jerky motion. How bloody annoying! I tried turning it off and I got a nice solid 191 frames per second. The animation is now nice and smooth and I'm quite happy with it.

Interesting that if I moved the polygon off the screen it added an extra 9 frames per second to my framerate! So when nothing was on the screen I got a result of 200 fps. I didn't think 1 stinking polygon would use up that many frames! lol.

Anyway thanks for your help. Looks like I'll just have to disable the firewall and unplug myself from the modem every time I want to test my program. Sheesh. :(


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Interesting that if I moved the polygon off the screen it added an extra 9 frames per second to my framerate! So when nothing was on the screen I got a result of 200 fps. I didn't think 1 stinking polygon would use up that many frames! lol.

Ah the common misconception that 9 FPS for a single polygon is alot of performance. I had the same misconception when i started out, you see 9 frames less with a framerate of 200FPS scene is probably less costly than 2 frames less in a 30FPS scene.

There is alot of other work done to render each frame such as
Clearing color/depth buffers
Submission of geometry
Entire Game loop/render loop

With 200FPS, your overhead per frame is very low, almost 0 in your case which is why a single polygon takes away 9 frames. In a proper game running at 30FPS, it will take much more additional detail/code in your scene to take away even a single frame of performance. Which is why many people will tell you that framerate is not a good gauge of performance.

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To add some numbers to GamerSg's post...
200 fps = 0.005 s/f (seconds per frame) = 5 ms/f (milliseconds per frame)
191 fps ~ 0.00524 s/f = 5.24 ms/f
So rendering your scene with that extra quad takes about 24 hundredths of a millisecond longer than rendering without it.
30 fps ~ 0.033 s/f = 33 ms/f
33.24 ms/f = 0.03324 s/f ~ 30.08 fps
With my rounding through those calculations we actually lose enough accuracy to show an increase in FPS. Without rounding we get...
30 fps = 0.0333... s/f = 33.333... ms/f
33.5689... ms/f = 0.0335689... s/f = 29.7894... fps
where ... doesn't necessarily mean those displayed digits repeat, just that there are more digits than I feel like pasting. [grin]

So if we're rendering at 30fps and we lose the same amount of time that we lost previously we would now be rendering at about 29.7894 fps. If we were rendering at 60 fps, the same difference in rendering speed corresponds to a new fps of about 59.16.

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Hey interesting stuff.

The program does practically nothing apart from checking direct input every frame, updating the performance counter and rendering the text and sprite. Next I'm gonna be adding physics and collision detection so I expect the framerate to drop fairly dramatically. Hopefully I can keep it around the 60fps mark. That is a nice frame rate to aim for.


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