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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 Rotating submodel

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I load an OBJ model into OpenGL. The model is a car. It consists of 5 submodels (groups) : frame, wheel1, wheel2, wheel3, wheel4. I use a rotation matrix to rotate the entire object around the 0 point (0,0,0). For each coordinate in the model I multiple with a rotation matrix, depending on the input. I made the functions so that the submodels can rotate around their midpoint (origin). The rotation of models around the point (0,0,0) or around their midpoint/origin works fine. However, I want to rotate the wheels forward, while the model/car is rotating around its origin. I thought to use rotation matrix rY. This is fine if the model is in position of Image A. However in Image B: the rotation matrix the Z coordinate does not change. So the positions aren't right anymore, if the model matrix is rotated. (See Image B.) I'm guessing I should use all 3 rotation matrixes somehow. The rotation matrix would depend on the 3 angles of rotation of the original model, but I dont know how. How would you rotate the wheels forward? (Could I also use a standard function of OpenGL?)

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Are you performing all of your rotations as 3x3 matrices? In 3d graphics transformation matrices are typically represented as 4x4 matrices, so that each matrix can store a rotation and a translation. If you only have 3x3 matrices I think that might be a problem for you, because you don't always want a rotation about an object's midpoint.

To do this properly you'd want to first rotate the wheel forward around its own midpoint, translate it to the proper position in the car, and then rotate it again around the center of the car.

Quote:
 (Could I also use a standard function of OpenGL?)

You can do this with OpenGL fixed function transformations. (These are depreciated, and you should learn to handle all of your matrix rotations yourself for forward compatibility, but they still work for now.) However you have to apply the transformations in reverse order due to the way the matrix multiplication stack works.

Assuming that your wheels rotate around the X axis by 45 degrees, and that the wheels are located at (+/- 1, 0, +/- 1) XYZ coordinates. Lets say you want to rotate the car by 30 degrees around the Y axis (up vector). This is what it would look like:

glLoadIdentity() //Reset everythingglRotatef(30,0,1,0)//Rotate the carDraw the Car frameFor Each Wheel(  glPushMatrix() //Save the original rotation matrix  glTranslatef(+/-1, 0, +/-1) //Move the wheel into position  glRotatef(45,1,0,0)//Rotate your wheel around its midpoint  Draw a wheel  glPopMatrix() //Load the original rotation matrix}

[I think I've got the rotations in the right order, but it has been a while since I used the fixed function equations, so someone can correct me if I've misspoke]

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The matrix is 3x3 (or 3xPolygonSize). I've the matrix stored in this way

It now works when I rotate the model around one axis (X,Y or Z) including the wheels. So Yaw, Roll or Pitch the object:
When using Yaw, Roll or Pitch the model goes back to its original position.
(inside: not drawn)

However when I do 2 or 3 rotations on the total model (for example coordinates*Ry and coordinates*Rz) it doesn't work. In other words, with for example Yaw and Pitch together the model doesn't get back in its original position.

I stored the total rotation of the angles, and wanted to rotate back with it.

So the problem is to get it back in it's original positions, when the model itself is rotated using 2 or 3 rotation matrixes.
I thought to do the rotations undone. (substracted), but this seems to work only in the first case.

I found out that if I do this in the opposite order that it was done, I get back into the intial position.

so:
pitch -92
yaw -92

However, if I do it in a different order it gets rotated, why is this?
Should I keep a list of each rotation that is done, or the order that the rotations of the total model is done?

[Edited by - walkaways on March 11, 2010 12:11:33 PM]

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Yes the order of rotations is very important, and if you change the order you will get different behavior.

You should take a look at the OpenGL Red Book, it will help you learn some fundamental concepts of 3d graphics, which should help you understand all of the questions you are asking.

There is a free online version (it is quite old, but the transformation concepts are still the same). Specifically in your case read through chapter 3: "Viewing"

Red Book Online Version

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I'll look into the book.
Because the order of rotation is important, should I store all rotations of the model in an array?
This would make it easy to reverse them all.

For example

orignal state -> pitch 30* -> roll 30* -> pitch 40* -> roll 30*

To get back to the original matrix position, one would go trough an array that contains this rotation in opposite direction, right?

curent_state -> roll -30* -> pitch -40* -> roll -30* -> pitch -30* -> original state

So to rotate the wheels in this situation from the original state:

roll -30* - pitch -40* - roll -30* - pitch -30* -> original state
rotate wheels
original state + rotated wheels -> pitch 30* - roll 30* - pitch 40* - roll 30*

Is it the 'right' way to keep an array of all rotations you've done with the model?

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For what reason do you feel the need to reverse your rotations? If you needed to get a matrix that "undid" all of your operations, then you would need to find the inverse of the original rotation matrix. You can do this by remembering all of the operations in reverse order, or there are other techniques for inverting a matrix that you can use. However I can't see why you would need to do this in your situation.

If you want to undo all your rotations (to draw another object for example), just reload the identity matrix, or better yet just use glPushMatrix/glPopMatrix (more appropriate for hierarchies).

For example if you have two cars you want to draw in different orientations:

//Do anything else in your scene you want.

glPushMatrix() //Store the current matrix on the stack
doCarRotations()
drawCar()
glPopMatrix() //we throw away the current matrix, and are back to what we had when we called pushmatrix
glPushMatrix() //save the matrix again
doCar2Rotations()
drawCar2()
glPopMatrix()

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I want to rotate the matrix back to the original position, so that I can rotate the wheels forward.

If I have the car in the following position:

I could Roll, Yaw or Pitch it around the midpoint, but neither of these will cause the wheel to roll forward.

If I rotate back to the original state, its easy to use Roll to move the wheel forward. Then I could rotate back to position in picture 1 and draw screen again.

Should I do it differently?

Side note: Im applying rotation matrixes directly to the original matrix, so the original matrix is not stored anywhere.

//xMatrix = ( cos( Theta * (PI/180)) * Matrix)   + (sin(Theta * (PI/180)))*Matrix[i+2];// zMatrix[i+2] = (-sin( Theta * (PI/180)) * Matrix)   + (cos(Theta * (PI/180)))*Matrix[i+2];

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You should not have to translate the wheel back to 0,0,0 to rotate it. If you rotate the wheel last, it will rotate on its local axis (assuming you perform the matrix operation in the right order). It should not matter if the car (and thus wheel) is upside down, flipped over, whatever. Put the wheel wherever you want it, and if you call glRotate last it will rotate on its own axis.

If you look at the sequence that I put in my first post, this should be all you need.

It looks like you are using your own matrix solution, which might be confusing you. Do you understand the difference between pre-multiplying or post-multiplying with your rotation matrix? It is not commutative. I will suggest that you try to get it working with OpenGL transformations until you get a better grasp for transformations, then you can go back and implement your own solution again if you prefer.

Anyway this is all covered in the Red Book chapter I mentioned, specifically pay attention to the section "Thinking about Transformations". Go read that and think about it for a few hours, and see if it makes more sense to you. If after studying that you're still having trouble then come back and we'll see what we can do.