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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 Shadow Mapping a Directional Light

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There seems to be plenty of articles about the shadow-mapping technique, and how to set OpenGL up to do it, but I find it exceptionally hard to find any material on how to create the light-source matrices. Here is an example of what I mean, from an online tutorial:
Pseudo-code in Pass 1:
PushState(ViewPort);
PushState(ViewMatrix);
PushState(ProjectionMatrix);
DrawScene();
PopState(RS_ProjectionMatrix);
PopState(RS_ViewMatrix);
PopState(RS_ViewPort);
The only thing holding me back right now is the creation of the shadowLightViewMatrix and shadowLightProjectionMatrix matrices, especially for directional lights. If I have a spotlight, it should be enough to match the cone of the light in my perspective matrix. I guess. But a directional light has no position. I must somehow position it to encapsulate the range of my main-camera frustum. I have never seen a tutorial explaining how to do this. Additionally, with either method, I need to select near/far planes that only barely encapsulate the geometry visible to them. And it needs to be orthogonal. How wide/tall do I make it? Can anyone explain how to derive these matrices? Thank you, L. Spiro

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The projection matrix for a directional light is just an orthographic projection - there isn't any need for perspective. To create it, you need to determine what the frustum size must be to fit your relevant geometry in it.

The view matrix can just be chosen to be from a position that allows your chosen frustum to encompass all of the needed geometry. Creation of the matrices is usually done by the D3DX library for me, but any standard graphics text should show the derivation of the matrices if you need that level of detail.

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In OpenGL there is a function glOrtho for creating orthographic projection matrix. As Jason Z wrote you can use any position for the light that is far enough to "see" all geometry that you want, because created shadows don't depend on the position in that case. The same goes for clipping planes. So everything is up to you :)

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I guess I was hoping for a sample of that math that appears in some texts, because it appears in none of the texts I have read. I left my books at work, but among them is Advanced Graphics Programming Using OpenGL (The Morgan Kaufmann Series in Computer Graphics), which again covers the concepts (which I understand clearly) but not the math.

I have a view frustum that is basically a pyramid with its top chopped off.
Then I have a box (representation of an orthogonal frustum projected from the directional light) at an arbitrary angle that needs to enclose that.
So I am guessing I need to take the dot product of the up/right vectors with the points that mark the corners of my view frustum to find the extremes in all directions, then take the objects that fit in that box and use a similar method to find the extreme far/near AABB’s of those objects.

Except there are no points in my view frustum; it is set up as 6 planes.
Calculating the intersection points of all the planes, while possible (and I know how to do it) seems slow, and I am sure there is a more efficient method.

As my engine is cross-platform (from iPhone to Nintendo Wii to Xbox 360), I will not be using any API-specific functions from OpenGL or DirectX.
I need the raw math behind this, or a pointer to a paper that has this mythical and mysterious math.
In the meantime I will of course continue searching for this, since you say it exists somewhere.

Thank you.
L. Spiro

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Hi!

like dys129 said, a common method go get the matrices in OpenGL is just to set the glOrtho and make a glGetMatrix(), but that's not really necessary. It is possible to set the matrices together by yourself, because a glOrtho() just multiplies an orthographic Matrix with the current Matrix (which is normally a Identity Matrix).

I don't know if you have seen that, but here you can see how OpenGL builds the orthographic Matrix:

http://www.opengl.org/sdk/docs/man/xhtml/glOrtho.xml

As said before, the values depend on you scene. For example I take:

glOrtho(-40,40,-40,40, 0.1f,500.0f);

I guess to calculate the best fit of your view frustum, it would be good to have the bounding spheres of the objects. Then you set the orthographic near plane on the nearest bounding sphere - radius (of it) and the farplane on the farthest bounding sphere + radius (of it).

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Thank you all for your replies.

The numbers I am interested in finding are the numbers that you would plug into glOrtho(). I know how to build the matrices; I do not know what numbers I am supposed to feed them.

glOrtho(-40,40,-40,40, 0.1f,500.0f);

How did you come upon 40?
Does it always encompass your full scene from your view frustum’s point of view?
I have a feeling that if it does then you have a special situation in your game.

I know that one option is to make one orthogonal projection that fits the whole world and just use that all the time. It also prevents shadow flicker when the camera moves.
But it is also the worst possible way to go; you have terrible depth precision and do not make full use of the limited texture space you have, which results in terribly low-resolution shadows.

So I want to snap the orthogonal projection to essentially be an AABB of the view frustum, and this is the math I need.
I proposed my idea for how to do this above, by taking extreme points of the view frustum in the up/right directions of the light vector, but I felt that this might not be the most efficient way (although it will work).
This is where I would get the width/height to feed into glOrtho() (or rather my own matrix functions).

It seems that everyone is suggesting I use the actual objects inside my main view frustum to derive the width/height of the orthogonal projection from the light. But I would run into the same math problem regarding how to size my orthogonal projection to fit them (although it does become simpler if I use their bounding spheres rather than their AABB’s, and if that is the way I go I would not need help with that math), however this method causes shadows to disappear when the object casting them is no longer in view. For example a tall building no longer casting a shadow on the street just because the player looks down.

But that method has the advantage of not needlessly stretching the orthogonal projection out into the distance of there are no objects out there, which increases the quality of the shadows.

I will size the orthogonal projection to fit my main view frustum (which I still need the math to do), then cull objects from that box, with the far plane being derived from the fitted box and the near plane being set back to the edge of my world box.
Then among those objects I will tighten the orthogonal projection using the bounding spheres of those objects (for which I do not need the math).

I wonder if this will be too computationally expensive.

I guess all I need is the method/math for fitting an orthogonal projection around a view frustum.

L. Spiro

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If I am in the wrong here, please forgive me, but I think I had a similar problem earlier.

These are a few steps to finding a good ortho frustum around your scene. Remember, that just because it is in the view frustum, there still exist objects outside the view frustum potentially that cast shadows into the view frustum (so you have to extend the box to include those).

This is how to calculate the minimum orthographic frustum around a arbitrary view frustum (as long as you can calculate it's eight corners).

1. Calculate the camera corners for your perspective transform in world space (To do this, calculate it in view space using trigonometry and then use the inverse view matrix to get the objects from view space to world space):

2. Rotate the vertices so that they are in the direction of the sun. To do this, I simply multiply every single corner by this matrix: gluLookAt (0, 0, 0, sx, sy, sz, 0, 1, 0) .

3. Now that you have the rotated vertices, it is a simple matter of finding the AABB around them, because you are in the light's view space. So find the maximum x, y, and z, values, and also the min x, y, and z values.

From here, you have the box, and creating an orthographic persepctive is trivial. The position of the camera will be at lightRotationInverse * (cx, cy, mz), where lightRotationInverse is the inverse of the matrix created in step 2, and (cx, cy, cz) is the center of the frustum in the light's view space, and mz is the minimum z value for the frustum's box.

There was a great XNA sample code that I used to determine how I should do this, but alas, I cannot find it. Search google for terms and add XNA maybe? I don't have the time to search.

Good luck!

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Thank you; this is essentially what I wanted.

In my original explanation of my idea I thought that calculating the 8 corners of the view frustum would be pretty expensive so I thought there must be another way to do it to get the orthogonal dimensions directly from the 6 planes (of the view frustum).
But I guess not. Seems I will have to get the actual corner points anyway.

In that case I can proceed, but I think (I could be wrong) that it would be faster to use the dot products of the up/right vectors of the directional light against all 8 points (as opposed to transforming them via the inverse view matrix of the light). Both methods require a loop over the vertices and a min/max comparison, but the dot product is cheaper than a matrix multiply with a vector.

I think this is what you found before:

If I am right, maybe you can even speed up your own implementation!
Just let me implement my idea first to see if it even works.

L. Spiro