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    • By elect
      ok, so, we are having problems with our current mirror reflection implementation.
      At the moment we are doing it very simple, so for the i-th frame, we calculate the reflection vectors given the viewPoint and some predefined points on the mirror surface (position and normal).
      Then, using the least squared algorithm, we find the point that has the minimum distance from all these reflections vectors. This is going to be our virtual viewPoint (with the right orientation).
      After that, we render offscreen to a texture by setting the OpenGL camera on the virtual viewPoint.
      And finally we use the rendered texture on the mirror surface.
      So far this has always been fine, but now we are having some more strong constraints on accuracy.
      What are our best options given that:
      - we have a dynamic scene, the mirror and parts of the scene can change continuously from frame to frame
      - we have about 3k points (with normals) per mirror, calculated offline using some cad program (such as Catia)
      - all the mirror are always perfectly spherical (with different radius vertically and horizontally) and they are always convex
      - a scene can have up to 10 mirror
      - it should be fast enough also for vr (Htc Vive) on fastest gpus (only desktops)

      Looking around, some papers talk about calculating some caustic surface derivation offline, but I don't know if this suits my case
      Also, another paper, used some acceleration structures to detect the intersection between the reflection vectors and the scene, and then adjust the corresponding texture coordinate. This looks the most accurate but also very heavy from a computational point of view.

      Other than that, I couldn't find anything updated/exhaustive around, can you help me?
      Thanks in advance
    • 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?
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OpenGL depth peeling for transparency?

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Last few days I have been looking into rendering techniques that I could use for creating a new game. Deferred rendering looks very appealing to me, because implementing it seems relatively simple. Things like multiple render targets I've already encountered, so I should be able to implement this (certainly because I found several good sources describing the technique, like the articles in GPU gems 2 and GPU gems 3 about deferred rendering). The biggest problem for me seems translucency. Both articles in GPU gems say they use a forward renderer for this, but they mention depth peeling as a possible solution. So I've been looking into depth peeling and I found a few articles: Interactive Order-Independent Transparency (nvidia, 2001) Multi-Layer Depth Peeling via Fragment Sort (microsoft, 2006) It seems an interesting technique, but then I see the performance measures from the second article: only 2 fps for a scene containing only several hundreds polygons and about 20 layers (it also mentions 4-5 fps for a scene with 15.000 polys and about 30 layers, so the results look very strange to me)!? Obviously, this is way too slow to be useful, probably even if you use only about 4 layers (I don't think you'll encounter 20 layers of transparency often). So, what is the current status about depth peeling? Is it considered as a useful technique? Are there alternatives that are better? And what kind of techniques are usual used for handling transparency? I couldn't find that much about it on the internet, does anybody know some more recent resources on the technique? [edit] Perhaps I should add the following: Target hardware is OpenGL 3.0/DirectX 10 capable graphics cards. Perhaps also (but this is less important) nVidia 7xxx and Ati 1xxx series. [/edit]

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The usual way of handling transparency is to render your transparent geometry after your opaque geometry in back-to-front order with z-buffer writing turned off. Thus, you have to calculate the transparent geometry's distance (along the camera's look axis) from the camera and sort by this z-depth. More complex transparent geometry might have to be split into smaller pieces to sort and draw correctly.

I don't believe depth peeling is a viable technique for a real game and it's not more useful in a deferred renderer than in a forward renderer.

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I've never implemented depth peeling myself, but since I read about it for the first time I've never really considered it a good solution for transparency - because of its efficiency issues and limitation of max. N transparent layers.

It's not acceptable for games even on highest end GPUs today. It's probably fine for some demos or other non-real time applications where perfect inter-translucency intersections are critical.

I'd definitely go with traditional forward renderer for translucency nowadays. Also because in a "typical" (thinking about games) scenario you don't have too many translucent surfaces.

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Original post by kek_miyu
I don't believe depth peeling is a viable technique for a real game and it's not more useful in a deferred renderer than in a forward renderer.

Well, depth peeling combined with deferred renderer for translucency has same advantage as it has with opaque geometry. You could theoretically light translucent geometry in deferred manner the same way as you light opaque geometry because each transparency layer contains single surface layer (although that would be overkill, hence you'd need separate depth buffer for each transparency layer as well).

But, yeah, depth peeling was mainly invented to handle problem of sorting translucent geometry back to front which can't be solved even if you sort per triangle.

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Original post by MickeyMouse
Original post by kek_miyu
I don't believe depth peeling is a viable technique for a real game and it's not more useful in a deferred renderer than in a forward renderer.

Well, depth peeling combined with deferred renderer for translucency has same advantage as it has with opaque geometry. You could theoretically light translucent geometry in deferred manner the same way as you light opaque geometry because each transparency layer contains single surface layer (although that would be overkill, hence you'd need separate depth buffer for each transparency layer as well).

But, yeah, depth peeling was mainly invented to handle problem of sorting translucent geometry back to front which can't be solved even if you sort per triangle.

I was thinking something like that. The idea was (more or less):
- create a G-Buffer for all opaque geometry, the usual way, this also fills the depth-buffer
- now start rendering transparent geometry, using the depth buffer you already created, this way you will only encounter transparent geometry that is actually visible
- the difference between the initial z buffer and the z buffer after a first transparency pass tells you the locations in which transparent geometry is visible, and this could perhaps be used for culling
- start depth peeling until you are on the same z level as the opaque geometry
- to do deferred rendering on the depth peeled geometry, you could use a second G-Buffer, for the transparent geometry, this G-buffer might be a bit simpler then your first one, because you might not need as much information for transparent geometry (depends on your needs).
- another option might be, using a G-buffer that is actually larger then your screen, and use the remaining space for transparent surfaces. Off course this means that you only have so much room for transparent surfaces. Advantage is that you could do deferred rendering for opaque and transparent geometry the same pass.

possible problems:
- what if you are standing just in face of a window, that would mean almost your entire screen is filled up with transparent geometry and that would mean a large (second) G-Buffer.

So this depends largely on the speed of the depth peeling for a typical scene, which depends on the amount of transparency in the scene and the number of levels of transparency. I might just try this approach and see how well it scales, depending on how hard it would be to implement (don't want to spend weeks, just to test how well it scales and probably find out it is way to complex and absolutely unusable).

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I should think it would be sufficient to do your normal, opaque-only deferred shading render first, as normal, and then with the Z-buffer still filled, do your translucent-surface rendering sorted back to front by objects; if you don't use double-sided surfaces and use only convex shapes, you should have few to no problems.

One issue tangled in is particle systems; particles can get everywhere, and it can completely ruin your scene if, say, the emitter for a particle stream gets sorted in front of a window, but some of its particles are behind it, causing them to be not rendered (Z-occlusion), or rendered as though the window wasn't there (insufficient data to reconstruct the window's effect on what's behind it).

Depth peeling resolves this by targetting that second issue; by rendering and saving enough data to reconstruct the window's effect, and then doing a composition pass of all the layers afterwards. But that doesn't mean it's an elegant solution, because you will still get artifacts if your scene gets viewed from an angle that lines up more transparent surfaces than you have layers.

My approach is simple, even if it does restrict the art of a scene a little bit; I don't organize my particles and dynamic transparent geometry by emitter, but by their 'sector' in a world made out of BSP-like planar slices, which are made from the relatively-static transparent geometry, like windows. My visible set of transparent surfaces is found by walking that tree and intersecting each sector with the viewing frustrum. I sort the visible sectors containing particles back to front, and render sector, partitions, sector, partitions, until I get back to the camera's sector.

This technique works fine for buildings, even somewhat curved ones, but I killed my poor CPU once when I, without thinking about the implication, made a dome-shaped glass greenhouse, and then raised a few dozen dust-cloud particles blowing around it. Just 120 or so surfaces to make the greenhouse, a subdivided icosahedron, but because of their orientation I was getting one dust-cloud every once in a while, while walking nearly 6,000 sectors.

On the plus side, it worked correctly. Not a single dust-cloud pixel was visible on the inside the greenhouse; you could see them blowing past outside, but the particles, though large, tried to intersect with the greenhouse walls and were clip-planed back to their rightful side. Because I could rely on particles staying in their sector on the far side of each partition (the greenhouse walls), I could do a distortion through the windows using the view rendered thus far, as well.

I give no promises to the performance of my technique; I am not a good optimizer, was not using deferred shading for the opaque geometry (though I don't see how it would change anything), and did everything by-the-book, using normal, unmodified algorithms instead of specializing everything to the problem domain. I think on my Radeon HD2600 & AMD Turion X2 2.0 GHz I just managed to break 9 frames per on a simple city scene, with transparent slice planes in the walls of buildings and a single unmoving car's windows (~20 slice planes).

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Original post by MJP
You should definitely have a look at this.

Ah, I had a quick look (tab still open, so I will look further) and I see it says texture array and Direct3D 10. Problem is: I work with OpenGL. You can't render to a 3D texture, or texture array's yet. I had a look into this yesterday, there is a very recent extension for OpenGL 2.1, which has texture arrays and it will be core functionality for OpenGL 3. So this might indeed be a very good solution, but not until my drivers support it.

I'll look further into this, to see what they say exactly.

As far as I could see, they exactly do what I thought, use an array of textures so that G-buffers can be created for multiple layers. The biggest drawback, besides it is not supported in OpenGL yet, is that it takes up huge amounts of memory, for example: a normal 128 bits G-buffer for a resolution of 1680x1050 (fairly common nowadays) takes up 27Mb of memory. Multiply this with the number of transparency layers you want to support and you know how much video memory your g-buffer uses.

I think it might be better to create a separate g-buffer for transparent surfaces. Because they mostly don't cover up your whole screen, you can use a stack of significantly smaller g-buffers for the transparent surfaces.

I'll think this whole thing true a bit better and see if I can implement it and see how it performs.

[Edited by - TheFlyingDutchman on September 15, 2008 5:21:14 PM]

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