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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 Problem with perspective

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I'm learning OpenGL and there's something really simple I'm missing about setting the perspective. (Yes, I've googled, read articles, many books, faqs, and tried lots of stuff.)

My understanding is that projection matrix transforms the eye space into clipping space. It seems like eye space can be whatever coordinates I want (meaning they can be outside the range of -1 to 1) and that the perspective matrix should handle transforming to clipping and NDC coordinates.

So, I would like to draw a 64x64 grid of points in the xz plane where the values go from 0 to 63. (Y is a positive constant.) I'm considering these to represent meters and want the grid to be shown in perspective and fill up most of the viewport. Sort of like looking at the ground or something. I can draw the points, but I'm having trouble figuring out how to set my projection matrix so that it draws in perspective and isn't really, really tiny. I've looked at diagrams and it seems like the left, right, top, bottom, near, and far should just be simple numbers indicating where in eye space you want the clipping edges to be.

So, for example, if I want points (0,10,0) through (63,10,63) to show up on the screen, I would set my left = 0, right = 63, top = 20 (or something), bottom = 0, near = 1 (I know it has to be positive), far = 64. But that just gives me a series of dots in in a very small part of the space. Therefore, the left, right, top, etc. must mean something else.

Can anyone explain?

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near = 10
or points
0,1,0 to 63,1,63.

It's perspective, so things further away are smaller. And 10 is further than 1. Much further....

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So, for example, if I want points (0,10,0) through (63,10,63) to show up on the screen, I would set my left = 0, right = 63, top = 20 (or something), bottom = 0, near = 1 (I know it has to be positive), far = 64. But that just gives me a series of dots in in a very small part of the space. Therefore, the left, right, top, etc. must mean something else.

Afaik those values are the left/right/top/bottom at the near plane, so your frustum is way bigger than you intend. Never really used glFrustum, since I pretty much moved from gluPerspective to building the matrix myself (and thinking in "normalized" values for z = 1 instead of z = near).

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Well, if I change the values to near = 1, far =2, left = 0, right =1, top = 1, bottom = 0 to make a smaller frustrum, it did make the area of points larger. Now, it's just a small area (about 1/5th of the viewport) rather than being a tiny area.

Yes, I understand they're the values of the near plane. (Found that in one of the tutorials I read.)

The statements I've seen are that projection maps the eye space to the clipping/NDC space. If that's true, then I would expect that by specifying my near plane (at 1) to have corners at left = 0, right = 63, top = 63, bottom = 0, that it would then map say coordinate (0,0,1) in eye space to coordinate (-1,0,0) in clipping space. And (63,0,1) to (1,0,0). And the rest of the coordinates between them on the x axes, and up to get the perspective.

In other words, I'm expecting the values for left, top, right, bottom to be the coordinate values of my eye space. So, based on my experiments, I would say that I don't understand eye space or the projection transformation (or both).

I'd love to just use my own matrices. (I prefer working with them actually.) But doing my own matrices won't help if I don't understand the basic concepts.

If anyone could point me to a perspective projection example that is not using NDC coordinates for the eye space so I can study how the modelview and projection matrices work that would be helpful.

@szecs

I didn't have my near set to 10. But I've just tried variations of setting my near and far with near being 10. But none of it helped. And how would that let me see objects close to the "camera" anyway?

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The statements I've seen are that projection maps the eye space to the clipping/NDC space. If that's true, then I would expect that by specifying my near plane (at 1) to have corners at left = 0, right = 63, top = 63, bottom = 0, that it would then map say coordinate (0,0,1) in eye space to coordinate (-1,0,0) in clipping space. And (63,0,1) to (1,0,0). And the rest of the coordinates between them on the x axes, and up to get the perspective.
[/quote]
This is correct if you do perspective (w) divide after the projection matrix. You don't need to worry about this if you're letting the API handle your projection through.

I don't quite understand all the terms you are using ('coordinate values of eye space'?), but it almost seems like you expect your view frustum to define a box, where the eye space coordinates go from 0 to 64 no matter how far away they are.

When you're using a perspective frustum, its like looking through the top of a pyramid. The near plane may be 0 to 63, but the far plane is much much larger than the near plane. Therefore if you have an object that is 64x64 that is located close the far plane, it appears much smaller than a 64x64 object near the near plane:

[attachment=2179:perspective.jpg]

If you know that you want to draw a 64x64 grid that fills the screen, why dont you just draw it orthographically? This shrinking is what perspective is, so if you don't want it to be shrunk than you shouldn't be using perspective projection.

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Hmm.... Well, most, if not all, of the instructional material I've read talk about OpenGL having eye space - which is often referred to as camera space, but since other people like to point out that there is no camera in OpenGL, I thought it would be better to use the term eye space since that's what the OpenGL website uses. And by coordinates, I mean the vertices in the eye space using whatever coordinate system the eye space is using (which might be different than object space or world space).

When I mean "fills the screen," I mean it fills it horizontally. For example, I'm trying to draw a flat piece of ground. I want the ground to look like ground that gets smaller in the distance. I realize that it won't fill the entire xy screen space. (It will be shorter.)

Orthographically won't work since I'm trying to look at scenery (eventually). The grid I'm trying to draw is 64x64 in the xz plane, not the xy plane.

The shrinking that I'm referring to is the entire plane, not the plane narrowing as it gets farther away. The way it looks now, the player is hovering way out in space looking at a distant piece of land. I want the player on the land, seeing it shrink toward the horizon.

Well, actually I expect the frustum to be defined by 6 planes - which are not a box. However, the functions ask for the numbers as left, right, top, bottom, near, far. These are scalar numbers, not 3d numbers. So, I don't know how to pick the scalar numbers to get the planes I want.

Do I need to transform my coordinates for my xz plane from what I have to something else - so that the perspective projection works and gives me a plane that fills the window horizontally (at the lower part) and narrows as it gets higher to show an horizon?

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The shrinking that I'm referring to is the entire plane, not the plane narrowing as it gets farther away. The way it looks now, the player is hovering way out in space looking at a distant piece of land. I want the player on the land, seeing it shrink toward the horizon.
[/quote]

I think you're confusing the point of the perspective matrix. If your eye is floating out in space and you want it parallel to the ground, this is a problem with your view matrix, not the perspective matrix.

The perspective matrix only handles the squashing of the eye space into a flat image, it doesn't determine from where you are viewing the scene. In fact you probably don't really need to calculate what near plane you want, usually an algorithm like that in gluPerspective (link) is sufficient, all you need to know is your near and far plane distance, and the FOV that you want.

Can you explain how you have formed your view/eye/camera matrix?

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Yes, that's it.

I read everything the responders have said - and decided that it must be a problem with my eye space (modelview). So, I started over with that. Several people here (and some of my google searching) gave me ideas about how to construct my modelview matrix. So, now I have something that looks reasonable. And I switched to a perspectivefieldofview function (which I think is similar to the gluPerspective function). I will look at your link.

It looks like the FOV is more important for what I'm doing (at this point) than the near/far values which I have at 1, 64. My FOV is PI/4.

I switched my coordinates back to +x, +y, -z (which I was using a few days ago).

And my new modelview matrix is.
1 0 0 0
0 1 0 0
0 0 1 0
-32 -36 0 10

where my xz plane is at y = 30 and x = [0..63] and z = [0..-63]. The number 10 is just a temporary value while I figure things out. (I need to do some calculations to see what value it should be to get the scale I want.) And the -32 is so that I'm looking at the centre of the plane. The -36 is so that the plane looks more like the ground. (I also need to do some calculations to see exactly what number this should be).

But now, I can proceed.

Thanks to everyone who responded.

I'll check back just in case anyone has any more ideas or pointers that I should think about.