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• ### Similar Content

• By elect
Hi,
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?

• 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.

• Hello!
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.
Features:
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
Initialization
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.)
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:
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:
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:

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.
glBindVertexArray(g_pGame->m_VAO);
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?
Test.gltf
Test.bin

• 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?

# OpenGL understanding opengl

This topic is 3934 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

## Recommended Posts

I realy dont understand this for some reason, ive simplified it below, and have the whole code below that. I understand it all, apart from these glLoadidentity() functions, take for example the render() function,
void Render()
{
glEnable(GL_DEPTH_TEST);				// enable depth testing

// do rendering here
glClearColor(0.0f, 0.0f, 0.0f, 0.0f);					// clear to black
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);		// clear screen and depth buffer

angle = angle + 0.5f;					// increase our rotation angle counter
if (angle >= 360.0f)					// if we've gone in a circle, reset counter
angle = 0.0f;

glPushMatrix();							// put current matrix on stack
glTranslatef(0.0f, 0.0f, -30.0f);	// move to (0, 0, -30)
//glRotatef(angle, 0.0f, 1.0f, 0.0f);	// rotate the robot on its y-axis
//glRotatef(angle, 1.0f, 0.0f, 0.0f);	// rotate the robot on its y-axis

DrawBoxes(0.0f, 0.0f, 0.0f);		// draw the robot
glPopMatrix();							// dispose of current matrix

glFlush();

SwapBuffers(g_HDC);			// bring backbuffer to foreground
}
1.clears the colour to black 2.clears screen 3. i believ here it sets everything back to 0, so x,y,z are now back to the centre of the screen, x=0,y=0, z=0 4.sets angle for rotation. 5.puts current matrix on stack, which is currently x=0,y=0, z=0 6. loads current matrix to x=0,y=0, z=0, (which isn't it that allready??) 7. move the camear back 30 in z 8. rotate camera 9. draw boxes now howcome we see the boxes from 30 steps backwards, because after the we move 30 steps backwards, we draw the boxes, so shouldn't they be drawn where we currently are, in which case the camera and boxex would be in the same z position. Because after we say glTranslatef(0.0f, 0.0f, -30.0f); isn'nt saying move to DrawBoxes(0.0f, 0.0f, 0.0f); going to put you in the same position, as open gl is a state machine, so that once glTranslatef(0.0f, 0.0f, -30.0f); is carried out the, the current position is now the origan. so DrawBoxes(0.0f, 0.0f, 0.0f); is'nt going to move you anywhere glTranslatef(0.0f, 0.0f, -30.0f); // move to (0, 0, -30) DrawBoxes(0.0f, 0.0f, 0.0f); // draw the robot
#define WIN32_LEAN_AND_MEAN				// trim the excess fat from Windows

/*****************************************************

Chapter 5: Robot Example

OpenGL Game Programming
Kevin Hawkins, Dave Astle

Animates a walking robot-like figure.

******************************************************/

////// Includes
#include <windows.h>					// standard Windows app include
#include <gl/gl.h>						// standard OpenGL include
#include <gl/glu.h>						// OpenGL utilties
#include <gl/glaux.h>					// OpenGL auxiliary functions

////// Global Variables
float angle = 0.0f;						// current angle of the rotating triangle
HDC g_HDC;								// global device context
bool fullScreen = false;

////// Robot variables
float legAngle[2] = { 0.0f, 0.0f };		// each leg's current angle
float armAngle[2] = {0.0f, 0.0f };

// DrawCube
// desc: since each component of the robot is made up of
//       cubes, we will use a single function that will
//		 draw a cube at a specified location.
void DrawCube(float xPos, float yPos, float zPos)
{

glTranslatef(xPos, yPos, zPos);
glBegin(GL_POLYGON);

glColor3f(255,0,0);
glVertex3f(0.0f, 0.0f, 0.0f);	// top face
glVertex3f(0.0f, 0.0f, -1.0f);
glVertex3f(-1.0f, 0.0f, -1.0f);
glVertex3f(-1.0f, 0.0f, 0.0f);

glColor3f(0,255,0);
glVertex3f(0.0f, 0.0f, 0.0f);	// front face
glVertex3f(-1.0f, 0.0f, 0.0f);
glVertex3f(-1.0f, -1.0f, 0.0f);
glVertex3f(0.0f, -1.0f, 0.0f);

glColor3f(0,0,255);
glVertex3f(0.0f, 0.0f, 0.0f);	// right face
glVertex3f(0.0f, -1.0f, 0.0f);
glVertex3f(0.0f, -1.0f, -1.0f);
glVertex3f(0.0f, 0.0f, -1.0f);

glColor3f(255,0,255);
glVertex3f(-1.0f, 0.0f, 0.0f);	// left face
glVertex3f(-1.0f, 0.0f, -1.0f);
glVertex3f(-1.0f, -1.0f, -1.0f);
glVertex3f(-1.0f, -1.0f, 0.0f);

glColor3f(255,255,0);
glVertex3f(0.0f, 0.0f, 0.0f);	// bottom face
glVertex3f(0.0f, -1.0f, -1.0f);
glVertex3f(-1.0f, -1.0f, -1.0f);
glVertex3f(-1.0f, -1.0f, 0.0f);

glColor3f(100,0,0);
glVertex3f(0.0f, 0.0f, 0.0f);	// back face
glVertex3f(-1.0f, 0.0f, -1.0f);
glVertex3f(-1.0f, -1.0f, -1.0f);
glVertex3f(0.0f, -1.0f, -1.0f);
glEnd();

}

// DrawRobot
// desc: draws the robot located at (xpos,ypos,zpos)
void DrawBoxes(float xPos, float yPos, float zPos)
{

DrawCube(0,0,0);

DrawCube(10,0,0);

DrawCube(0,10,0);

DrawCube(10,10,0);

}

// Render
// desc: handles drawing of scene
void Render()
{
glEnable(GL_DEPTH_TEST);				// enable depth testing

// do rendering here
glClearColor(0.0f, 0.0f, 0.0f, 0.0f);					// clear to black
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);		// clear screen and depth buffer

angle = angle + 0.5f;					// increase our rotation angle counter
if (angle >= 360.0f)					// if we've gone in a circle, reset counter
angle = 0.0f;

glPushMatrix();							// put current matrix on stack
glTranslatef(0.0f, 0.0f, -30.0f);	// move to (0, 0, -30)
//glRotatef(angle, 0.0f, 1.0f, 0.0f);	// rotate the robot on its y-axis
//glRotatef(angle, 1.0f, 0.0f, 0.0f);	// rotate the robot on its y-axis

DrawBoxes(0.0f, 0.0f, 0.0f);		// draw the robot
glPopMatrix();							// dispose of current matrix

glFlush();

SwapBuffers(g_HDC);			// bring backbuffer to foreground
}

// function to set the pixel format for the device context
void SetupPixelFormat(HDC hDC)
{
int nPixelFormat;					// our pixel format index

static PIXELFORMATDESCRIPTOR pfd = {
sizeof(PIXELFORMATDESCRIPTOR),	// size of structure
1,								// default version
PFD_DRAW_TO_WINDOW |			// window drawing support
PFD_SUPPORT_OPENGL |			// OpenGL support
PFD_DOUBLEBUFFER,				// double buffering support
PFD_TYPE_RGBA,					// RGBA color mode
32,								// 32 bit color mode
0, 0, 0, 0, 0, 0,				// ignore color bits, non-palettized mode
0,								// no alpha buffer
0,								// ignore shift bit
0,								// no accumulation buffer
0, 0, 0, 0,						// ignore accumulation bits
16,								// 16 bit z-buffer size
0,								// no stencil buffer
0,								// no auxiliary buffer
PFD_MAIN_PLANE,					// main drawing plane
0,								// reserved
0, 0, 0 };						// layer masks ignored

nPixelFormat = ChoosePixelFormat(hDC, &pfd);	// choose best matching pixel format

SetPixelFormat(hDC, nPixelFormat, &pfd);		// set pixel format to device context
}

// the Windows Procedure event handler
LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
static HGLRC hRC;					// rendering context
static HDC hDC;						// device context
int width, height;					// window width and height

switch(message)
{
case WM_CREATE:					// window is being created

hDC = GetDC(hwnd);			// get current window's device context
g_HDC = hDC;
SetupPixelFormat(hDC);		// call our pixel format setup function

// create rendering context and make it current
hRC = wglCreateContext(hDC);
wglMakeCurrent(hDC, hRC);

return 0;
break;

case WM_CLOSE:					// windows is closing

// deselect rendering context and delete it
wglMakeCurrent(hDC, NULL);
wglDeleteContext(hRC);

// send WM_QUIT to message queue
PostQuitMessage(0);

return 0;
break;

case WM_SIZE:
height = HIWORD(lParam);		// retrieve width and height
width = LOWORD(lParam);

if (height==0)					// don't want a divide by zero
{
height=1;
}

glViewport(0, 0, width, height);		// reset the viewport to new dimensions
glMatrixMode(GL_PROJECTION);			// set projection matrix current matrix

//// calculate aspect ratio of window
gluPerspective(54.0f,(GLfloat)width/(GLfloat)height,1.0f,1000.0f);

glMatrixMode(GL_MODELVIEW);				// set modelview matrix

return 0;
break;

default:
break;
}

return (DefWindowProc(hwnd, message, wParam, lParam));
}

// the main windows entry point
int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nShowCmd)
{
WNDCLASSEX windowClass;		// window class
HWND	   hwnd;			// window handle
MSG		   msg;				// message
bool	   done;			// flag saying when our app is complete
DWORD	   dwExstyle;						// Window Extended style
DWORD	   dwstyle;						// Window style
RECT	   windowRect;

// temp var's
int width = 800;
int height = 600;
int bits = 32;

//fullScreen = TRUE;

windowRect.left=(long)0;						// Set Left Value To 0
windowRect.right=(long)width;						// Set Right Value To Requested Width
windowRect.top=(long)0;							// Set Top Value To 0
windowRect.bottom=(long)height;						// Set Bottom Value To Requested Height

// fill out the window class structure
windowClass.cbSize			= sizeof(WNDCLASSEX);
windowClass.style			= CS_HREDRAW | CS_VREDRAW;
windowClass.lpfnWndProc		= WndProc;
windowClass.cbClsExtra		= 0;
windowClass.cbWndExtra		= 0;
windowClass.hInstance		= hInstance;
windowClass.hIcon			= LoadIcon(NULL, IDI_APPLICATION);	// default icon
windowClass.hCursor			= LoadCursor(NULL, IDC_ARROW);		// default arrow
windowClass.hbrBackground	= NULL;								// don't need background
windowClass.lpszClassName	= "MyClass";
windowClass.hIconSm			= LoadIcon(NULL, IDI_WINLOGO);		// windows logo small icon

// register the windows class
if (!RegisterClassEx(&windowClass))
return 0;

if (fullScreen)								// fullscreen?
{
DEVMODE dmScreenSettings;					// device mode
memset(&dmScreenSettings,0,sizeof(dmScreenSettings));
dmScreenSettings.dmSize = sizeof(dmScreenSettings);
dmScreenSettings.dmPelsWidth = width;			// screen width
dmScreenSettings.dmPelsHeight = height;			// screen height
dmScreenSettings.dmBitsPerPel = bits;				// bits per pixel
dmScreenSettings.dmFields=DM_BITSPERPEL|DM_PELSWIDTH|DM_PELSHEIGHT;

//
if (ChangeDisplaySettings(&dmScreenSettings, CDS_FULLSCREEN) != DISP_CHANGE_SUCCESSFUL)
{
// setting display mode failed, switch to windowed
MessageBox(NULL, "Display mode failed", NULL, MB_OK);
fullScreen=FALSE;
}
}

if (fullScreen)								// Are We Still In Fullscreen Mode?
{
dwExstyle=WS_EX_APPWINDOW;					// Window Extended style
dwstyle=WS_POPUP;						// Windows style
ShowCursor(FALSE);						// Hide Mouse Pointer
}
else
{
dwExstyle=WS_EX_APPWINDOW | WS_EX_WINDOWEDGE;			// Window Extended style
dwstyle=WS_OVERLAPPEDWINDOW;					// Windows style
}

// class registered, so now create our window
hwnd = CreateWindowEx(NULL,									// extended style
"MyClass",							// class name
"OpenGL Robot",		// app name
dwstyle | WS_CLIPCHILDREN |
WS_CLIPSIBLINGS,
0, 0,								// x,y coordinate
windowRect.right - windowRect.left,
windowRect.bottom - windowRect.top, // width, height
NULL,									// handle to parent
hInstance,							// application instance
NULL);								// no extra params

// check if window creation failed (hwnd would equal NULL)
if (!hwnd)
return 0;

ShowWindow(hwnd, SW_SHOW);			// display the window
UpdateWindow(hwnd);					// update the window

done = false;						// intialize the loop condition variable

// main message loop
while (!done)
{
PeekMessage(&msg, hwnd, NULL, NULL, PM_REMOVE);

if (msg.message == WM_QUIT)		// do we receive a WM_QUIT message?
{
done = true;				// if so, time to quit the application
}
else
{
Render();

TranslateMessage(&msg);		// translate and dispatch to event queue
DispatchMessage(&msg);
}
}

if (fullScreen)
{
ChangeDisplaySettings(NULL,0);					// If So Switch Back To The Desktop
ShowCursor(TRUE);						// Show Mouse Pointer
}

return msg.wParam;
}



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Quote:
 Original post by wforl1.clears the colour to black2.clears screen3. i believ here it sets everything back to 0, so x,y,z are now back to the centre of the screen, x=0,y=0, z=04.sets angle for rotation.5.puts current matrix on stack, which is currently x=0,y=0, z=06. loads current matrix to x=0,y=0, z=0, (which isn't it that allready??)7. move the camear back 30 in z8. rotate camera9. draw boxesnow howcome we see the boxes from 30 steps backwards, because after the we move 30 steps backwards, we draw the boxes, so shouldn't they be drawn where we currently are, in which case the camera and boxex would be in the same z position.Because after we say glTranslatef(0.0f, 0.0f, -30.0f); isn'nt saying move to DrawBoxes(0.0f, 0.0f, 0.0f); going to put you in the same position, as open gl is a state machine, so that once glTranslatef(0.0f, 0.0f, -30.0f); is carried out the, the current position is now the origan. so DrawBoxes(0.0f, 0.0f, 0.0f); is'nt going to move you anywhereglTranslatef(0.0f, 0.0f, -30.0f); // move to (0, 0, -30) DrawBoxes(0.0f, 0.0f, 0.0f); // draw the robot

Except that there is no "camera", camera is just an illusion. You have one world transformation which transforms your vertices. You can think of the "camera" as stuck at the origin looking in one direction and the rest of the world moving around it. You don't actually move the "camera" you change how the vertices are transformed making it seem as if there is a camera.

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It's as Omid says.
When you do a glTranslate, you move the "origin of the world", and not the viewpoint/view frustum.

If you grab a pen and hold it in front of you (I'm serious... grab that pen, it'll help), and the tip of the pen is the origin of the world. A translate would move the tip of the pen, but you will stay in the same position. You stay fixed in your chair and all you are doing is move the tip of the pen around the screen.

So if you do a glTranslate(0,0, -30), you move the tip of the pen 30 units into the screen. Your view/camera/eyes will stay where they are. Whatever you draw now at position 0,0,0, the tip of the pen, will "appear" to be 30 units away from you.

Now, things get more complicated if you start doing multiple translations and rotations because they are additive, and it will become important that you understand how the world transformation matrix is manipulated, and how glPushMatrix and glPopMatrix are your best friends.

But I'll leave it with that. Try to understand how a translate and rotate affect the world, rather than the "view".