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• 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.

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:
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 Text-rendering and forward-compatibility

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I am creating my own game engine, and I am trying to make it as forward-compatible with opengl as possible. This means not using depreciated features of opengl like the modelview matrix and display lists and the like. While I'm ok with using vertex attribute arrays for everything, I'm at a loss of how to reproduce the functionality that display lists give me. For example, text rendering. The way I currently render text is to store the font faces as a bunch of textures (or perhaps one big one) and map that texture on to a quad, one quad for each character. I draw each character at a 'cursor position' and then advance the cursor position by the width of the character. I currently store these texture quad calls and cursor advancement in a display list, one for each glyph in the font. This makes it convenient to draw text because all I have to do now is use glCallLists() with the text string itself. But now display lists are depreciated, and there is no way to store uniform matrix multiplication operations (i.e. how I advance the 'cursor' every character) into a sort of buffer you can call repeatedly anymore. What am I to do to keep this forward-compatible, yet fast? Perhaps I could use instanced draw calls and put every glyph dimensions and texture offsets into a uniform buffer, and use the text string as a uniform array to use gl_InstanceID for the character being rendered, and use the string to determine which character we are rendering in that instance, but the font would have to be monospace. Something tells me I'm overthinking this and perhaps I'm trying too hard to avoid legacy coding. [Edited by - Cathbadh on February 8, 2010 1:28:16 PM]

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You could create a vertex buffer and index buffer. Load the index buffer such that every 6 indices draws two triangles. Before drawing, load the vertex buffer so that every 4 vertices (indexed by 6 indices) will draw a character quad. Loop the vertex buffer adjust the positions for each set of 4 vertices to be where you want the character drawn, the next 4 vertices, will be character 2, so on, also adjust the texture coordinates to pull the correct character coordinates from one large texture. The index buffer wouldnt need to be updated. You could load the vertex buffer with enough space to draw, a single 64 or 128 character line at a time, If you need more less or in a different position, adjust your draw calls and call counts. Once the first 4 vertices are in the correct place, the second character position and size can be adjusted based on the one before it.

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This won't be particularly easy, but I would recommend something along the following lines:

3. Use the instancing extension to render a single quad N times, where N is the number of characters.
4. Use the instance ID to calculate the position the quad should be rendered (in the vertex shader).
5. Use the instance ID to find the character in the string texture (in the fragment shader).
6. Use the character to render the correct portion of the font texture.

I am pretty sure that this is the fastest possible approach to text rendering, although variations are possible, for instance: using a geometry shader or histopyramid expansion, rather than the instancing extension.

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That's just it-- I know how to use element arrays and vertex buffers, I just miss the ability to just be able to (after some lengthy setup with generating font bitmaps and display lists) give opengl my text string and nothing more, and have it draw the text to the screen correctly. I'd like to not have the cpu involved in anything more during runtime. Is this a pipe dream? I know I can get monospace fonts to work like I stated above because I know that characters are all the same width, so I can figure out where to place a quad simply by gl_InstanceID * glyph_width, but the moment glyph_width is not constant across all characters, all bets are off.

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Quote:
 Original post by CathbadhThat's just it-- I know how to use element arrays and vertex buffers, I just miss the ability to just be able to (after some lengthy setup with generating font bitmaps and display lists) give opengl my text string and nothing more, and have it draw the text to the screen correctly.
My method will do that. Upload the string as a 1D texture, bind the shader and a single call to drawInstanced
Quote:
 I'd like to not have the cpu involved in anything more during runtime. Is this a pipe dream?
Nope, just a fair amount of work to implement.
Quote:
 I know I can get monospace fonts to work like I stated above because I know that characters are all the same width, so I can figure out where to place a quad simply by gl_InstanceID * glyph_width, but the moment glyph_width is not constant across all characters, all bets are off.
Use a second texture containing widths for each glyph.

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I think I am already saving a lot of cycles by rendering the text to an offscreen framebuffer and just plastering that framebuffer on top of the view as just a single big quad. On-screen text doesn't change very often, so I figure it would be redundant to have it draw that string of text over and over again. The text is processed and rendered to the FBO only when the text changes.

It is just bugging me that I can get legacy opengl to do variable-width fonts, and I can't figure out a way to get the core spec to do it too with the same runtime complexity.

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Quote:
Original post by swiftcoder
Quote:
 Original post by CathbadhThat's just it-- I know how to use element arrays and vertex buffers, I just miss the ability to just be able to (after some lengthy setup with generating font bitmaps and display lists) give opengl my text string and nothing more, and have it draw the text to the screen correctly.
My method will do that. Upload the string as a 1D texture, bind the shader and a single call to drawInstanced
Quote:
 I'd like to not have the cpu involved in anything more during runtime. Is this a pipe dream?
Nope, just a fair amount of work to implement.
Quote:
 I know I can get monospace fonts to work like I stated above because I know that characters are all the same width, so I can figure out where to place a quad simply by gl_InstanceID * glyph_width, but the moment glyph_width is not constant across all characters, all bets are off.
Use a second texture containing widths for each glyph.

Your method is essentially what I was thinking about in the OP, but using uniform buffers and uniform blocks instead of 1D textures. I can specify character width in a uniform block just fine, but the problem is that I cannot sum up the widths of all the previous characters to determine where the shader should place the instanced quad. It'd be great if I could somehow store the progress of the cursor across the screen in a uniform during shader execution, but as we all know uniforms are read-only in shaderland.

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Quote:
 Original post by CathbadhI can specify character width in a uniform block just fine, but the problem is that I cannot sum up the widths of all the previous characters to determine where the shader should place the instanced quad. It'd be great if I could somehow store the progress of the cursor across the screen in a uniform during shader execution, but as we all know uniforms are read-only in shaderland.
Uniforms aren't the only way to pass data around. Either geometry shaders or a variation on histopyramid expansion would allow you to sum up the variable distances for each character.

If you want an even simpler solution, and you know the length of the string on the CPU, use a multi-pass approach. Attach an empty 1D texture to a framebuffer object, and in the first pass, render the width of each character into its location. Then in consecutive passes, shift the texture containing the string one character to the right, and add to the existing value. For a string of length N, after N-1 passes you will have the correct offset of each character.

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Since the text change rarely, I think it's better to calculate those offsets on the cpu. It's indeed simpler to implement and easier to understand than the above gpu-based methods. Moreover, you only have to do it when the text change and only once, so it will never be your bottleneck.

EDIT: It's also a lot simpler to implement multi-line layouts or features like kerning doing it in the cpu.

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Quote:
 Original post by apatriarcaSince the text change rarely, I think it's better to calculate those offsets on the cpu.

Not only the offsets, but the entire text rendering. Rendering bitmap fonts on the CPU is dirt cheap, and vector fonts aren't slow either. Both are highly multithreadable. And since text usually doesn't change multiple times per frame, it's a rather low frequency operation. It's a waste to use GPU geometry shaders or similar to recomposite something 60 times per second that changes once every ten minutes or so.

Just render all text on the CPU (if possible in parallel to the GPU doing something else) into a cache texture, and upload the new data on-demand to the GPU. The latter would then render entire words or rows using a single quad.

BTW, just to clear up a misconception here: the 'old style' one glyph per display list call thing was maybe convenient for the developer, but it was anything but fast. It was (and is) one of the least efficient ways to render text short of plotting glyphs using large amounts of GL_POINTS... (which ironically could even be faster than the display list thing on modern GPUs !)