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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.

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 Help! GS StreamOutput..

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## Recommended Posts

Hello, I'm new of D3D, and i have a problem with the stream output feature..

What i need is to output a single structure (a float4, to be precise) per GeometryShader invocation.
The problem is that the geometry shader generates a triangle strip or a line strip, so the vertexcount is never 1, and, even if i can set the maxvertexcount to some number, the number of actual elements of the TriangleStream or LineStream is variable.

So what i wonder is whether it is possible to output only one float4 even if the Geometry Shader sends a list of various elements to the rasterizer..

Should this be not possible (I'm afraid it's not as the api seemingly do not really let me specify it), is there another way to do the same?
I thought of writing to a UAV from the GS, but i'm on nVidia hardware, and this seems to be not supported.
I also thought of what in OpenGL would be a texture buffer object  +  the extension to write textures (ext_image_load_store).
Is there something equivalent in D3D11?

thanks!

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You can stream output a PointStream (more info here), so it can be one float4 per GS invocation.

EDIT:

I think I misunderstood your question...

You want to send a triangle/line stream to the rasterizer and stream output to a PointStream in the same geometry shader right?

When using multiple output streams, all streams must contain points, and up to one output stream can be sent to the rasterizer. More commonly, an application will not rasterize any stream.

So, unless there's a trick that I don't know, I think you'll have to use two passes, one to stream output points, and a second to rasterize triangles or lines.

This is how particle systems are implemented using the geometry shader. 1st update each particle in the GS and stream output, and then use a different GS that expands the particles to quads and sends them to the pixel shader.

Edited by TiagoCosta

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You can actually stream output and rasterize at the same time, you just use multiple stream outputs in your geometry shader.  You would append the single float4 to your stream output stream, and then just send your other geometry out another stream to be rasterized.  Have you tried that out yet?  Perhaps if you could show your steam output declaration entries, it might help to understand what you are currently set up for.

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Thanks a lot, Tiago and Jason.
Thiago's solution would indeed work. I admit i did not think about that since i was doing everything in one pass in OpenGL. But with some small performance penalty it would make things work..
But Jason says it's possible to do everything in the same pass? this is interesting so i don't have to change the algorithm..

I made a simple example of what i'm trying to do... A trivial effect that takes in input a bunch of vertices, expand them to triangles, and attempts to output a new, x-shifted position to a buffer.
With such GS, would it be possible to output to a buffer only a single vertex per GS invocation, even if i send a long triangle strip to the rasterizer?

And also, if my GS states "maxvertexcount(n)", does it mean that for each invocation of the GS, i should at least account for(and so allocate)  n possible entries in the output buffer?

Below the code:

/* UNIFORMS */

extern const float4x4 matMetersToTexture;
extern const float4x4 matProjectionTransformation;

StructuredBuffer<float4> positionin		: register( t0 );
StructuredBuffer<float4> positionorig		: register( t4);

// UAV  for writing
//RWStructuredBuffer<float4> positionout		: register( u0 );   // Doesnt work with nVidia Kepler.

float4 pullData(uint idx)
{
return positionin[idx];
}

float3 pullCoords(uint idx)
{
float4 p;
p = positionin[idx];
float3 vecCoords = float3(0,0,0);
vecCoords.xy = p.xy;
return vecCoords;
}

float2 metersToTexture(float3 vecVertexCoords)
{
float2 vecTexCoords;
vecTexCoords =  (  mul(  matMetersToTexture , float4(vecVertexCoords,1.0) )   ).xy;
return vecTexCoords;
}

float2 metersToCamera(float2 vecCoords)
{
float2 vecScreenCoords =  (  mul(  matProjectionTransformation , float4(vecCoords,0.0,1.0) )   ).xy;
return vecScreenCoords;
}

struct MYVS_OUTPUT
{
float4 pos : SV_Position; // screen coordinate
float3 tex : TEXCOORD0;   // texture coordinate
//uint   vertexID : SV_VertexID; // Invalid.
};

MYVS_OUTPUT IDToVertexTransformVS (uint idx: SV_VertexID)
{
MYVS_OUTPUT output;
output.tex = float3(0,0,0);
output.pos = float4(0,0,0, 1);

float3 vecInputCoords = pullCoords(idx);
float2 vecTexCoords = metersToTexture(  vecInputCoords  );

output.tex.xy = vecTexCoords;
output.pos.xy = metersToCamera(vecInputCoords.xy);

return output;
};

struct MYGS_OUTPUT
{
float4 pos : SV_Position; // screen coordinate
float3 tex : TEXCOORD0;   // texture coordinate
float4 color:  COLOR0;
};

struct MYGS_STREAMOUTPUT {
float4 newpos : Position; // new screen coordinate
};

[maxvertexcount(3)]
point MYVS_OUTPUT input[1],
uint iPrimID : SV_PrimitiveID,
inout TriangleStream<MYGS_OUTPUT> triangleStream
inout PointStream<MYGS_STREAMOUTPUT> pointStream)
{
const float fWidth = 0.055;

float4 vecData = pullData(iPrimID);
float2 vecCoords = vecData.xy;
float2 vecPos   = metersToCamera(vecCoords);

float4 vecVertex0 = float4(vecPos,0.0,1.0) + float4(-(fWidth * 0.5),-(fWidth * 0.5),0.0,0.0);
float4 vecVertex1 = float4(vecPos,0.0,1.0) + float4((fWidth * 0.5),-(fWidth * 0.5),0.0,0.0);
float4 vecVertex2 = float4(vecPos,0.0,1.0) + float4(0.0,(fWidth * 0.5),0.0,0.0);
float4 vecColor;
vecColor = float4(0.8,0.0,0.0,1.0);

MYGS_OUTPUT outputStructure;
outputStructure.color = vecColor;
outputStructure.tex = input[0].tex;

// Base triangle 0
outputStructure.pos =  vecVertex0;
triangleStream.Append( outputStructure );
outputStructure.pos =  vecVertex1;
triangleStream.Append( outputStructure );
outputStructure.pos =  vecVertex2;
triangleStream.Append( outputStructure );

//triangleStream.RestartStrip();

MYGS_STREAMOUTPUT streamOutputStructure;
streamOutputStructure.newpos = float4(vecData.xy + float2(0.01,0.0), vecData.zw);
pointStream.Append(streamOutputStructure);
}

struct PS_OUTPUT {
float4 color : SV_Target0; // pixel color
};

PS_OUTPUT pstest (MYGS_OUTPUT input)
{
PS_OUTPUT output;
//output.color = float4(1,0,1,1);
output.color = input.color;
return output;
}

/* TECHNIQUES */

technique11 showpoints
{
pass P0
{
SetBlendState(OverBlendingWithStraightInAndPremultipliedOut, float4(0.0f, 0.0f, 0.0f, 0.0f), 0xFFFFFFFF);

"Here goes something that specifies the data in the SO to the rasterizer. Ideally all the content in the MYGS_OUTPUT",
"Here goes something that specifies the data in the SO to the buffer. Ideally all the content in MYGS_STREAMOUTPUT",
NULL,
NULL,
0);
}
}

Edited by paoletto

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Concerning Tiago's suggestion, i was also wondering what i should put as the last parameter of ConstructGSWithSO(), in the case i don't want to rasterize any stream.
And also how to specify the same thing on the client side, since i use D3DX11CreateEffectFromFile()  , which from what i understood, calls automatically CreateGeometryShaderWithStreamObject()

thanks!

Edited by paoletto

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I haven't ever done this with the effects framework, but here is what you would do if you were manually setting the parameters:

1. Fill out the D3D11_SO_DECLARATION_ENTRY elements to enumerate your streamed out data items.  I presume you are already doing this somewhere in your C++ code.  This is also what declares which data is going into which stream.

2. When you create the geometry shader with ID3D11Device::CreateGeometryShaderWithStreamOutput method, you specify which stream gets rasterized in the RasterizedStream argument.

Thus it should be possible for you to define two streams, one for rasterization of the triangle stream and one for point outputs that goes to the stream output buffer.

The max vertex output is a limitation supplied mostly for the driver to efficiently allocate enough memory for each invocation of the GS.  Your stream output buffer should be at least big enough to hold whatever sized data you are planning to store in it!