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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 fastest way to render lots of small changing objects

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I am developing a 2d-like graphics system for games, using lots of different algoritms for creating nice dynamic graphics. Up till now, I have always used glBegin and so forth for the rendering, and learned fairly recently that this was not the way to go for optimal performance. So, I learned about VBO, and just now got it working - but it was wayyy slower, probably because am I not doing it right. My current approach is this: * creation Create VBO for all objects (if may be thousands) I use GL_STREAM_DRAW_ARB setting because I will update the data each frame. No matrix transformations is used. I put data for vertice, color and texture coords next to each other in the vbo for each object. * update I use glBindBufferARB and glMapBufferARB to get the gpu pointer, and then iterate the datavalues for vectors, colors and texturecoordinates and insert them into the pointer, then glUnmapBufferARB. * draw glEnableClientState for GL_VERTEX_ARRAY, GL_COLOR_ARRAY and GL_TEXTURE_COORD_ARRAY, specify pointers for them with the correct offset and then glDrawArrays. DisableClientState and BindBuffer to id 0. --- now, this was very slow compared to my usual approach using glBegin/glEnd. What am I doing wrong? Since I have seperate opengl drawing/blending settings for each gfx-object, I can't just put out all VBO-s at the same time using one large VBO.( can I? ) Does the gpu choke because of my large number of VBOs? I have another idea (based on how I THINK things work). I create _one_ VBO with the largest amount of data I think I will use for each gfx-object (usually about 20 vertices). Then, I use the same VBO all the time when inserting data and rendering, instead of thousands of small ones because I will not render them all at once anyway. Is the VBO-aproach suitable for loads of small objects with different opengl-settings? thanks for any help and suggestions!

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Quote:
 Original post by RockardSince I have seperate opengl drawing/blending settings for each gfx-object...
Herein lies your problem. The main benefit of VBO (or vertex arrays) is to allow you to render as much geometry as possible with a single draw call. If your objects really do need different drawing/blending settings (and they probably shouldn't), you should group them by matching settings, and collect each group in a VBO, and then render each group with a single call.

Unless you are doing something really strange though, you shouldn't need to set the blend equations more than a couple of times per frame - in a typical game, you disable blending, render all opaque objects, and then re-enable blending to render all the transparent objects.

Also, how many objects are we talking about, and what target hardware? I render 200-300 objects per frame, each with their own VBO, containing around 100 vertices, and my rendering is so far overshadowed by AI and physics, that it doesn't provide noticeable overhead.

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First, glBegin is quite fast compared to what people usually say.
But if you want to be cross-API it's not a good idea to use them anyway :)

VBO is the standard way of rendering. The solution for you I would be to create a big VBO. Like 400 vertices.

Then render your sprites by changing values in it incrementally.

BatchVBO[offset + 0].x = ...
... offset + 1
etc

Then when everything is ready for render, draw BatchVBO with the number of vertices you want to render. You dont have to render it all :)

This was, you update only once into the video card, it's very fast.

If you run out of vertices (400, or whatver max you put), just render it, and continue by starting at 0 again.

Using that technic you might want to sort by texture though. Or if order is important, render the batchVBO when you need to switch texture and start again at 0.

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This is something that's come up a few times before, and no one has mentioned this: when you have a large VBO shared by many objects (sprites), you can no longer use GL's rotate/translate -- you have to transform all the verts on the CPU.

Doesn't this somewhat undermine the speed gained by using VBOs? Especially since simpler 2D games are most likely not GPU-bound..

[Edited by - raigan on July 13, 2008 11:09:06 AM]

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Quote:
 Original post by raiganThis is something that's come up a few times before, and no one has mentioned this: when you have a large VBO shared by many objects (sprites), you can no longer use GL's rotate/translate -- you have to transform all the verts on the CPU.

Yes, you can use GL's rotate/translate and glLoadMatrixf, etc even when you have multiple objects in 1 VBO. That's what I do and have been doing for years.

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Quote:
 Original post by V-manYes, you can use GL's rotate/translate and glLoadMatrixf, etc even when you have multiple objects in 1 VBO. That's what I do and have been doing for years.

Could you explain how?

I can understand how this would work if you only had a few complex objects sharing a buffer -- as long as you have few objects, you have few draw calls and this makes sense.

But in the context of drawing a lot of 20-vertex objects (as the OP is doing) or Daivuk's suggestion, I'm confused about how this would work -- wouldn't you have to issue a separate DrawElements call for each unique transform? And doesn't this undermine the whole reason for using VBOs?

Each sprite in a 2D engine will have a unique transform, so that's one draw call per quad -- just as bad as immediate mode.

If you're using VBOs to get proper large-batch 2D drawing as swiftcoder described ("The main benefit of VBO (or vertex arrays) is to allow you to render as much geometry as possible with a single draw call") then I don't see how you can avoid transforming the geometry on the CPU. But I'm hoping that I'm missing something obvious..

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1. I've found that if you've got completely dynamic objects (like sprites) then there's no performance difference between VBOs and regular vertex arrays. (Unless you're re-rendering the same sprites multiple times a frame, like for some kind of post process).

2. Yes, that means you have to do the transformations yourself. This ends up being trivial in the large scale of things though.

3. I find the following works very well:
- Find all visible sprites/objects
- Sort by depth/texture/gl state as appropriate.
- Go through the sorted list, adding to a single big vertex array. Keep adding sprites that have the same GL state. When the state changes, flush the array (draw it) then continue adding sprites to it. Repeat until out of sprites.

This means you build up batches on the fly for each frame. You'll usually only use a few different blending modes, so that helps keep batches large. Also use sprite sheets/texture atlases so you can draw lots of different sprites without having to flush the list to change texture.

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Quote:
 Original post by raiganCould you explain how? I can understand how this would work if you only had a few complex objects sharing a buffer -- as long as you have few objects, you have few draw calls and this makes sense.But in the context of drawing a lot of 20-vertex objects (as the OP is doing) or Daivuk's suggestion, I'm confused about how this would work -- wouldn't you have to issue a separate DrawElements call for each unique transform? And doesn't this undermine the whole reason for using VBOs? Each sprite in a 2D engine will have a unique transform, so that's one draw call per quad -- just as bad as immediate mode.If you're using VBOs to get proper large-batch 2D drawing as swiftcoder described ("The main benefit of VBO (or vertex arrays) is to allow you to render as much geometry as possible with a single draw call") then I don't see how you can avoid transforming the geometry on the CPU. But I'm hoping that I'm missing something obvious..

Yes, you would issue a DrawElements call per object.

Quote:
 And doesn't this undermine the whole reason for using VBOs?

The reason to use VBO is to keep data on the GPU. If you have dynamic data, the reason is we assume is that's what the driver prefers.

Why store multiple objects in 1 VBO?
To reduce GL state changes.
You would have to call glBindBuffer less often. You would call gl***Pointer less often as well.

In terms of performance gain for a simple sprite rendering engine, I have no idea if it will improve performance since I'm not working on one.

Immediate mode, vertex arrays, compiled vertex arrays, display lists are also other ways. As you can see, GL has many ways to send data.
What is specific about VBOs is that it is for storing vertex/indices only.
The driver decides if it should be placed in VRAM or elsewhere..

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Another reason to batch small objects into VBO's is for caching. You have to hit that sweet spot where you have enough geometry in the VBO so it doesn't have to keep going back for stuff, and too much geometry in the VBO where it can't fit the whole thing into the cache. Right now from what I've read on these boards, VBO's should be in the neighborhood of 1MB to 4MB, but as technology changes, so too will these numbers.

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Wow!
Incredibly great responses and lots of valuable discussions!

I will try out the approach of first making a big VBO, then keep inserting
vertices until some of the gl-options differ - by then, I draw and start over again. This approach will work great with my current problem with loads of bullets of the same type. Right now, I can put out about 3000 with 4 vertices each with vsync at 60 fps - more bullets and the fps will drop. I think it is the enormous amount of openglcalls that kills the performance.

This approach of collecting vertices dynamicly will probably also work wonders for a tilesystem I will insert later. I was first thinking about making this stupid solution about sorting stuff manually in groups using bit-settings... man that would have been a waste of time!

Hohooo I'm so excited! I will begin coding my new system right away.
I'm really hoping I will break that 3000 bullets barrier.
I'll will report my results.