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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? 
      Will it be just smart rendering or something else is required?
    • By jsquare89
      I am somewhat new to game development and trying to create a basic 3d engine. I have managed to set up a first person camera and it seems to be working fine for the most part. While I am able to look up, down, left and right just fine the camera is constrained to the mouse movement in the window (i.e when the mouse reaches edges of the window it discontinues camera rotation and mouse is out of window bounds. I tried to use SDL_WarpMouseInWindow(window, center.x,center.y) but when I do this then it messes up the camera and the camera is stuck, even though there is some slight movement of the camera, it keeps going back to the center.
      void Camera::UpdateViewByMouse(SDL_Window &window, glm::vec2 mousePosition)
      float xDistanceFromWindowCenter = mousePosition.x - ((float)1024 / 2) ;
      float yDistanceFromWindowCenter = ((float)720 / 2) - mousePosition.y;
      yaw = xDistanceFromWindowCenter * cameraRotationSpeed;
      pitch = yDistanceFromWindowCenter * cameraRotationSpeed;
      SDL_WarpMouseInWindow(&window, 1024 / 2, 768 / 2); }
      i’ve been stuck on this for far too long. any help would be much appreciated
      i have also tried relative mouse movement,  and .xrel and .yrel to avail. polling mouse state with sdl_event. I do also know that SDL_WarpMouseInWindow makes change to event and have tried also ignore and reenabling to no avail
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OpenGL Problems with camera movement and rotation.

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Hi guys. I am trying to learn how to operate my camera in OpenGL. However I think I have problems with understaind the translations in local \ global coordinate system. I want to move my camera freearly around a cube which is located at (0,0,-5). However instead of moving my camera the sceene looks like the cube is moved to the orgin of global coordinate system. Also the rotation of my camera doesn't look "natural" to me. Something is wrong with that also. Here is a crucial part of my code: procedure ReSizeGLScene(Width, Height: Integer); cdecl; begin if Height = 0 then Height := 1; glViewport(0, 0, Width, Height); glMatrixMode(GL_PROJECTION); glLoadIdentity; gluPerspective(45, Width / Height, 0.1, 1000); glMatrixMode(GL_MODELVIEW); glLoadIdentity; end; procedure GLKeyboard(Key: Byte; X, Y: Longint); cdecl; begin if Key = 27 then Halt(0); case Key of 97: CameraPosition.Z := CameraPosition.Z + 1; 122: CameraPosition.Z := CameraPosition.Z - 1; end; end; procedure GLSpecialKeyboard(Key: Longint; X, Y: Longint); cdecl; begin case Key of GLUT_KEY_LEFT: CameraAngle.Y := CameraAngle.Y - 1; GLUT_KEY_RIGHT: CameraAngle.Y := CameraAngle.Y + 1; GLUT_KEY_DOWN: CameraAngle.X := CameraAngle.X + 1; GLUT_KEY_UP: CameraAngle.X := CameraAngle.X - 1; end; end; procedure DrawGLScene; cdecl; begin glClear(GL_COLOR_BUFFER_BIT or GL_DEPTH_BUFFER_BIT); glLoadIdentity; glRotatef(CameraAngle.Y, 0, 1, 0); glRotatef(CameraAngle.X, 1, 0, 0); glTranslatef(CameraPosition.X, CameraPosition.Y, CameraPosition.Z); glutWireCube(1); glutSwapBuffers; end; Also, the full working program can be downloaded here: http://www.speedyshare.com/files/21386187/MyCamera.zip The effect which I want to achive is to point my camera towards some point in scene and move camera towards that point. Thanks for your time.

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If you want to look at a specific object/position, you can just use the glLookAt() at function. However, if you're trying to freely rotate your camera, the rotation matrix based on the rotation of the camera won't do. You must use the inverted matrix of the camera's rotation.

EDIT: If the inverted matrix is your solution, let me know. It's a bit of a pain in the ass and I've got a working implementation here somewhere that I can post.

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Thank you for your reply.

I want to move my camera freerly like in a 3D Space game.

Could yu give me an example how to use such inverted matrix?

Firstly I need to create a rotation matrix umm...from my angles?
Than I need to converted it to the inverted matrix?
And than I need to multiply that matrix by the current view matrix?

EDIT: Yes, that is exactly what I need, thank you for your help. But will I be able to understand your implementation? I mean I need to learn how to use such matrix to achieve a given result.

[Edited by - Wodzu on March 12, 2010 8:40:14 AM]

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I'm probably jumping ahead and should be careful not to make this more confusing than it really is. It's been a while since I've had to delve into OpenGL so I need to get my bearings.

Okay, I see you're using a glRotatef() call for each axis. This is a pretty straightforward method so you can scratch my earlier comment about inverted matrices. This method (for me anyway) tends to require some trial and error. For instance, (and this is going on memory alone) you may need to negate the coordinates before translating:
glTranslatef(-CameraPosition.X, -CameraPosition.Y, -CameraPosition.Z);

instead of:
glTranslatef(CameraPosition.X, CameraPosition.Y, CameraPosition.Z);

If you think about this logically, the objects in your screen space appear to move in the opposite direction of the camera movement. Looking out of a train window (left) as the train moves forward (right), the train station appears to move opposite (left).

Also, I don't see where you're cube's position is being set and it appears that the cube should be at origin. To shift the position:

glPushMatrix (); //preserve the camera rotation matrix
glTranslatef (0.0, 0.0, -5.0); //shift the cube position
glMultMatrixf (Obj->GetRotation()); //if you need to rotate the cube, do it here
glutWireCube (1); //same as before
glPopMatrix (); //retrieve the camera rotation matrix

Hope this helps!

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In case you need it at any time in the future, here's an implementation of the invert matrix function in BASIC:

DIM Adjoint(11) AS SINGLE
DIM AS SINGLE Determinant = Source[0] * (Source[5] * Source[10] - Source[9] * Source[6]) - _
Source[4] * (Source[1] * Source[10] - Source[9] * Source[2]) + _
Source[8] * (Source[1] * Source[6] - Source[5] * Source[2])
DIM AS SINGLE DetRec = 1.0 / Determinant 'Determinant reciprocal

'Calculate minors of source matrix
Minor(0) = Source[5] * Source[10] - Source[9] * Source[6]
Minor(1) = Source[4] * Source[10] - Source[8] * Source[6]
Minor(2) = Source[4] * Source[9] - Source[8] * Source[5]
Minor(4) = Source[1] * Source[10] - Source[9] * Source[2]
Minor(5) = Source[0] * Source[10] - Source[8] * Source[2]
Minor(6) = Source[0] * Source[9] - Source[8] * Source[1]
Minor(8) = Source[1] * Source[6] - Source[5] * Source[2]
Minor(9) = Source[0] * Source[6] - Source[4] * Source[2]
Minor(10) = Source[0] * Source[5] - Source[4] * Source[1]

'Calculate cofactors and adjoint in one shot
Adjoint(0) = Minor(0)
Adjoint(1) = -Minor(4)
Adjoint(2) = Minor(8)
Adjoint(4) = -Minor(1)
Adjoint(5) = Minor(5)
Adjoint(6) = -Minor(9)
Adjoint(8) = Minor(2)
Adjoint(9) = -Minor(6)
Adjoint(10) = Minor(10)

'Finally, we find the inverse by dividing the adjoint by
'the determinant |A|. Since you can't divide a matrix,
'we simply multiply each value by the reciprocal.
FOR Y = 0 TO 2
FOR X = 0 TO 2
Index = Y * 4 + X
Dest[Index] = DetRec * Adjoint(Index)

'Last column can simply be copied
Dest[3] = Source[3]
Dest[7] = Source[7]
Dest[11] = Source[11]

This inverts ODE (physics) matrices so the format is different than OpenGL. Here's another function that performs the conversion:

SUB RenderConvertODEMatrix (Source AS dReal PTR, Dest AS GLFloat PTR)
Dest[0] = Source[0]:Dest[1] = Source[4]:Dest[2] = Source[8]:Dest[3] = 0
Dest[4] = Source[1]:Dest[5] = Source[5]:Dest[6] = Source[9]:Dest[7] = 0
Dest[8] = Source[2]:Dest[9] = Source[6]:Dest[10] = Source[10]:Dest[11] = 0
Dest[12] = 0:Dest[13] = 0:Dest[14] = 0:Dest[15] = 1

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Thank you codrex75 for the answers.

However you said that I do not need the inversion matrix but then you propose me to use glMultMatrixf(). So I am totaly lost now...

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A little primer to help your understanding:

So when dealing with cameras and objects, you have two matrices that you need to worry about. One is the Model Matrix, and the other is the View matrix. These are often combined together to get the "ModelView" matrix that you will often hear of.

When you define a mesh, all of the coordinates will typically be in "Object Space". This defines the location of vertices relative to the origin of your object. The object space coordinates have no information about where the object is in the "World" (or Global Coordinate System). If you have a cube at 0,0,0 and you translate the cube to another position, the object space coordinates are always the same, because they only define vertices relative to the object.

So if we want to move our cube to a new location, we need to find a way to move each vertex from "Object Space" into "World Space". This is done via a Model Matrix. If you want to translate your object 5 units to the right, then you define a Transformation Matrix that defines a translation to the right by five units. This matrix can be 'M', or our model matrix. So now if we have a point 'p' in object space, and we want to move it into world space 'P', we transform it with the Model matrix like so: P = Mp. Your model matrix can contain as many translations, rotations, scalings as you need. If you want to Translate, then rotate, then scale your model, via matrices To (T object), Ro, So, then your modelview matrix is constructed M = To*Ro*So.

But what about the view matrix? Because there is no camera construct in OpenGL, we must transform our vertices again into a new space called "Eye Space". The viewport in opengl always looks out from 0,0,0 in the negative z direction, so we must "transform the entire world" so that it looks accurate from that space.

As coderx was describing with the train analogy, you move your view in openGL by moving the entire world in the opposite direction. When you turn your head to the right, this is exactly the same thing as if the entire world is rotating to the left. When you move your eyes up, it is also as if the entire world is moving down. So however we want to move our "camera", we must transform the world by the inverse of this movement.

So we need to come up with a matrix V (view matrix), that transforms our world coordinates into eye coordinates. Using our original point p and model matrix M, the equation now looks like this: P = VMp, where P is now in eye space.

Now remember that V is supposed to be the inverse of the camera movement that we want. Lets say what we really want to do is move our camera up and then rotate it 45 degrees downward to get a birds eye view of our world. If we treat the camera like an object, then we want to transform our camera by a translation (Tc) and a rotation (Rc): C = Tc*Rc.

Now transform matrix C will take an object and translate it up and rotate it. But what we really want is the inverse of C, which will be our view matrix. inverse(C) = C' = V

Now to find C' (also known as V), you can either invert the matrix C using matrix inversion methods, or you can just compute it from the original transformations. Because of the properties of matrices, this holds true:

C' = (TcRc)' = Rc'Tc'

Where Tc and Rc are our camera transforms. However Tc' and Rc' are very easy to calculate. The inverse of a translation is just a translation in the opposite direction, and the inverse of a rotation is just a rotation in the opposite direction.

So now you can transform your original vertex into eye space like so:

P = Rc' * Tc' * To * Ro * So * p


P = VMp

You can either construct this by building the "VM" matrix yourself, or you can build it with opengl transform functions. For example:

glLoadIdentity(); //Modelview matrix now identity
//Setup the camera
glRotatef(negative camera rotation) //Modelview matrix now = Rc'
glTranslatef(negative camera movement) //Rc' * Tc'
//Setup the model matrix
glTranslatef(object translation) //Rc' * Tc' * To
glRotatef(object rotation) //Rc' * Tc' * To * Ro
glScalef(object scale)//Rc' * Tc' * To * Ro * So

//Now send your object space vercices, which are translated into eye space
glVertex(p) // P = Rc' * Tc' * To * Ro * So * p

And that concludes the basics of opengl cameras :)

I know it is confusing at first, but after you work at it for a while it will make more sense.

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Thank you karwosts for you explanation and your time.

You expleined it very nicely even nicer the the OpenGL book itself ;)

There is one thing strictly mathematical which I do not know how to calculate.
I have some ideas but I do not want to reinvent the wheel.

Lets assume that I've rotated mine camera view about three angles. So I have now new vector pointing in space. I would like to move my camera along this vector by some unit distance. So I need to know how much I must translate in X,Y,Z-plane.

I know how to do this in 2D-space but I do not know how to do this in 3D, atleast in easy way.

The idea which I have is that:

I have old vector and 3 angles. I need to rotate this vector and calculate it's new coordinates. When I have new coordinates I normalize the vector and multiply by the unit distance. Then I add this value to the calculated vector.

But this is a lot of work and I am redoing some thing which is already done by the OpenGL.

How to do it in a simpler way? The ideal way would be to know only how much I need to translate without calculating the new vector by myself.


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Actually this information is stored inside the model matrix for you and easy to pull out. When you look at the actual elements of the matrix, this is what they represent:

0 4 8 12
1 5 9 13
2 6 10 14
3 7 11 15

Rx Ux Ox Px
Ry Uy Oy Py
Rz Uz Oz Pz
0 0 0 1

So elements 0,1,2 are the Right Vector (Rx, Ry, Rz), 4,5,6 is the Up Vector, and 8, 9, 10 is the Out Vector (or direction). 12,13,14 contain your translation. So whenever you perform the matrix math you already have your out vector. If you want to use the OpenGL transformations instead of performing the matrix op's yourself (preferred way is to do it yourself, but that is more advanced), you can download the matrix with glGetFloatfv and examine it's elements.

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Thank you karwosts :)

I have now a working camera however it is made after trials and errors and I feel that i know only in half how it works :|

I know that the order of command isue is crucial due to the matrix multiplication.
Howeve I can not find a logic in it. I wanted to compare two thhe most simple cases to observe how to rotation occurs.

Here are the cases:


gluLookAt(0,0,5, 0, 0, 0, 0, 1, 0);
glRotatef(90, 1, 0, 0);
glRotatef(90, 0, 1, 0);


gluLookAt(0,0,5, 0, 0, 0, 0, 1, 0);
glRotatef(90, 0, 1, 0);
glRotatef(90, 1, 0, 0);

So I only switched the order of rotation commands.

What I find illogical and impossible to understand (after rotating this damn cube for hours;)) is that:

In first case when I am thinking in terms of grand fixed orgin the command are issued in the reversed order, so:

1. Cube is drawn
2. Cube is rotated around OY counterclockwise by 90 degrees.
3. Cube is rotated around OX counterclockwise by 90 degrees.
4. Cube is translated -5 units in Z direction from the orgin.

Am I thinking correct?

But the same thinking in CASE two fails me, here it is:

1. Cube is drawn.
2. Cube is rotated around OX counterclockwise by 90 degrees.
3. Cube is rotated around OY counterclockwise by 90 degrees.
However the effect is different from expected! It looks like the step 2 (rotation around OX) also rotated the OY axis by 90 degrees! But in first case rotation around OY did not rotate the OX axis. This is the thing which I do not udenrstand.

Why in the first case the coordinate system has not been rotated with object and in the second case coordinate system has been rotated.

I can not see the logic here. Eiter in both cases the coordinate systems should be rotated with an object or they should stay fixed.

I am lost... :|

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