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OpenGL What to use,where to start (robot arm simulation)

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Hello!

I'm looking for some advices to getting started with a graphic programming related subject.

This is my last semester in my electrical engineering studies. We got a project to make a 5-axis robot arm. My part was to build its software side, controlling the motors,receiving position information of the servos and images from the attached camera.

Now we need to upgrade it and i decided to make a simulation part for the software.

At first i want to make something similar to this(without the text of course):

http://www.societyofrobots.com/images/robot_arm_FBD.png

- want to display its joints(axis-points) and arms
- providing enough information (x,y coords) and using forward/inverse kinematics i want it to find a certain point on the canvas (considering some restriction like angles)
- my final goal is to implement this whole thing in 3d with a rigged 3d model

My first thought was to use OpenGL, but i'm not sure if it's the best consedering the fact that i have only 3 months until the deadline and never done anything like this. 

So should i stick to OpenGl or find an engine?

And also don't know that what technique could do this trick, i read little about bone animation but it's really not my field.

I would be grateful for any advices,experiences,resources you can share with me to start this journey.

Thank you in advance.

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1.  Are you doing a 3D version of the picture or just something in 2D just like that?

 

2.  What programming language / OS is the project?

 

3.  How familiar are you with the math behind 3D graphics?  Vectors, matrix transformation, projects, etc.

 

OpenGL is very difficult to learn.  There are lots of little problems that come up.  

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My part was to build its software side, controlling the motors,receiving position information of the servos and images from the attached camera.

 

That is a large task list. You don't mention any previous experience with real-time 3D rendering, or your familiarity with programming in general. If you have none or just "some," and considering your limited time (unless you can devote 24-7 to it), I would recommend that you (at least) start with a simpler interface, possibly 2D. Just learning about rigged 3D model animation can be a very lengthy process by itself, and you mention possibly having to get the I/O set up, and displaying or otherwise interfacing with camera images. Just FYI, I have a bit of experience with that sort of thing. Though some time ago, I worked as an instrument engineer interfacing instruments of various types (including LVDTs and stepmotors) to a project. Given only 3 months, your first task is to settle on a design that is implementable in that timeframe.

 

If you decide to continue with a 3D model, you may want to consider finding an existing application of some sort that displays an animated model. I am most familiar with animation of skinned meshes using matrices in DirectX and Direct3D 11, for which you can get the flavor in this article, though the principles are applicable to any 3D API. You may also want to browse the Graphics Programming and Theory articles here on gamedev for other possibilities. Several may be of interest. Take note of the tab labeled "Articles" just below the gamedev logo above on this page.

 

Other considerations:

 

- Creating a rigged 3D model from scratch using a modeling program such as Blender has its own learning curve. Alternatively, spend some time looking for an existing model that could be easily modified for your purpose. In either case, count on spending some time becoming familiar with the concept.

 

EDIT: If you have access to books (or a budget for same), the older versions (possibly the newer versions also) of the Red Book (OpenGL "Bible") specifically discussed the math and rendering of a robot arm. Frank Luna (author) has good books for both DirectX 9 and Direct3D 11 with extensive information on skinned mesh animation.

 

EDIT2: Unless you're an absolute whiz with programming analog and digital I/O boards, consider that you may have to generate and test some code for accessing the device real time that supports your rendering needs.

 

EDIT3: You don't mention your math capabilities - you will need to be quite familiar with 3D vectors, matrices and quaternions to support your app. When you get into rendering, you will need to understand row-major vs. column-major matrices, conversion of matrices to quaternions (and vice-versa), etc. Several APIs have math libraries available to do most of that work for you. Just sayin'

Edited by Buckeye

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Hello!
 
First of all I would like thank you to expended your time on me.

 

1.  Are you doing a 3D version of the picture or just something in 2D just like that?

 

2.  What programming language / OS is the project?

 

3.  How familiar are you with the math behind 3D graphics?  Vectors, matrix transformation, projects, etc.

 

OpenGL is very difficult to learn.  There are lots of little problems that come up.  

 

Sorry i forgot to mention some info smile.png

 

1. At first I would like something simple so i will stick to 2D. My final goal will be something like you can see in this presentation:


 

2. I would like to use Qt with C++ under Linux OS (ubuntu 12.04)

 

3. We have been thought for these things at the university(not particularly for 3D graphic but the basis of linear algebra) but unfortunately not on an advanced level. 

 

 

 


That is a large task list. You don't mention any previous experience with real-time 3D rendering, or your familiarity with programming in general. If you have none or just "some," and considering your limited time (unless you can devote 24-7 to it), I would recommend that you (at least) start with a simpler interface, possibly 2D.

 

You are absolutely right,  that's why i would like to make something like a linked above at first then move one step forward. I have strong background in C programming and a moderate one in OOP. So I think programming won't be my weak spot but the mathematic much rather clearly understanding and implementing them in my app.

That's great to see that the Red Book covers this topic, there are some available copies in the library thanks for the tip. Besides that I see I need to get my hands on a book which related to graphic mathematics.

 

 

 


Take note of the tab labeled "Articles" just below the gamedev logo above on this page.

 

Great I will look around there.

 

 

 


Creating a rigged 3D model from scratch using a modeling program such as Blender has its own learning curve. Alternatively, spend some time looking for an existing model that could be easily modified for your purpose. In either case, count on spending some time becoming familiar with the concept.

 

The 3D model is done just as the rigging. The only problem is that i have no clue at all how they will be manipulated in a program how will it know about the rigging (skeleton).
But as I mentioned the manipulation of my rigged 3D model  is the last line on my to-do list. 

 

 

 


You don't mention your math capabilities - you will need to be quite familiar with 3D vectors, matrices and quaternions to support your app.

 

I have some basic knowledge of them but of course I need to lose my self in the topic.I would be grateful If you can provide any link which is for begginers and clear to understand.
 


Several APIs have math libraries available to do most of that work for you.

 

http://en.wikipedia.org/wiki/List_of_3D_graphics_libraries

Do you have any background from any of them (except DirectX that you mentioned )? Which one would you recommend for a begginer like me consedering the task to be done?

 

Thank you for helping!
 

Edited by Shaoboy

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Given you skill level and time constraints, I would suggest SFML.  I would use this only for 2D, but if you decide to add some 3D, you can use the SFML for the base application.. Either way, I think it's easy enough that you can use it, but robust enough that you won't be limited.

 

http://www.sfml-dev.org/

 

Good luck with whatever you choose.

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The 3D model is done just as the rigging. The only problem is that i have no clue at all how they will be manipulated in a program how will it know about the rigging (skeleton).
But as I mentioned the manipulation of my rigged 3D model is the last line on my to-do list.

 

Not sure what your first sentence means, unless you mean the model and rigging would be done together. That is the most common approach. With regard to deforming the model (mesh) with the skeleton, that's what the article I linked above discusses. In any case, leaving 3D for later sounds like a good choice.

 


Do you have any background from any of them (except DirectX that you mentioned )?

 

Some in OpenGL a long time ago. That's why I knew about the robot simulation mentioned in the Red Book. Other than that, I'm afraid not. Glass Knife seems to be pointing you in a good direction.

 


[math] I would be grateful If you can provide any link which is for begginers and clear to understand.

 

There are some articles here on gamedev (same tab but under Technical->Math and Physics). Googling for "matrix quaternion tutorials" yields quite a few pertinent hits, many of them graphics oriented. "Clear to understand .. quaternions?"  wink.png We're talkin' quaternions here. Oxymoronic.  However, in particular, the graphics oriented math tutorials should get you started or refreshed in that area.

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Given you skill level and time constraints, I would suggest SFML.  I would use this only for 2D, but if you decide to add some 3D, you can use the SFML for the base application.. Either way, I think it's easy enough that you can use it, but robust enough that you won't be limited.
 
http://www.sfml-dev.org/
 
Good luck with whatever you choose.

 

Thank you so much I will give it a try. smile.png

 


Not sure what your first sentence means, unless you mean the model and rigging would be done together.

 

Exactly meant that smile.png Until now I have used the "3D model" term without stating that it's rigged, just the pure model. Thank you for correcting me.


With regard to deforming the model (mesh) with the skeleton, that's what the article I linked above discusses. In any case, leaving 3D for later sounds like a good choice.

 

Sorry I slip through that line I definitely check it out!

 


"Clear to understand .. quaternions?"  We're talkin' quaternions here. Oxymoronic.

 

That's what I'm afraid of biggrin.png but google is my friend and the topics you mentioned above as well so i think there will be no problem smile.png

 

 

Thanks both of you there is now something i can follow.

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      Another important thing that pipeline state object encompasses is the input layout description that defines how inputs to the vertex shader, which is the very first shader stage, should be read from the memory. Input layout may define several vertex streams that contain values of different formats and sizes:
      // Define input layout InputLayoutDesc &Layout = PSODesc.GraphicsPipeline.InputLayout; LayoutElement TextLayoutElems[] = {     LayoutElement( 0, 0, 3, VT_FLOAT32, False ),     LayoutElement( 1, 0, 4, VT_UINT8, True ),     LayoutElement( 2, 0, 2, VT_FLOAT32, False ), }; Layout.LayoutElements = TextLayoutElems; Layout.NumElements = _countof( TextLayoutElems ); Finally, pipeline state defines primitive topology type. When all required members are initialized, a pipeline state object can be created by IRenderDevice::CreatePipelineState() method:
      // Define shader and primitive topology PSODesc.GraphicsPipeline.PrimitiveTopologyType = PRIMITIVE_TOPOLOGY_TYPE_TRIANGLE; PSODesc.GraphicsPipeline.pVS = pVertexShader; PSODesc.GraphicsPipeline.pPS = pPixelShader; PSODesc.Name = "My pipeline state"; m_pDev->CreatePipelineState(PSODesc, &m_pPSO); When PSO object is bound to the pipeline, the engine invokes all API-specific commands to set all states specified by the object. In case of Direct3D12 this maps directly to setting the D3D12 PSO object. In case of Direct3D11, this involves setting individual state objects (such as rasterizer and blend states), shaders, input layout etc. In case of OpenGL, this requires a number of fine-grain state tweaking calls. Diligent Engine keeps track of currently bound states and only calls functions to update these states that have actually changed.
      Binding Shader Resources
      Direct3D11 and OpenGL utilize fine-grain resource binding models, where an application binds individual buffers and textures to certain shader or program resource binding slots. Direct3D12 uses a very different approach, where resource descriptors are grouped into tables, and an application can bind all resources in the table at once by setting the table in the command list. Resource binding model in Diligent Engine is designed to leverage this new method. It introduces a new object called shader resource binding that encapsulates all resource bindings required for all shaders in a certain pipeline state. It also introduces the classification of shader variables based on the frequency of expected change that helps the engine group them into tables under the hood:
      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. Shader variable type must be specified during shader creation by populating an array of ShaderVariableDesc structures and initializing ShaderCreationAttribs::Desc::VariableDesc and ShaderCreationAttribs::Desc::NumVariables members (see example of shader creation above).
      Static variables cannot be changed once a resource is bound to the variable. They are bound directly to the shader object. For instance, a shadow map texture is not expected to change after it is created, so it can be bound directly to the shader:
      PixelShader->GetShaderVariable( "g_tex2DShadowMap" )->Set( pShadowMapSRV ); Mutable and dynamic variables are bound via a new Shader Resource Binding object (SRB) that is created by the pipeline state (IPipelineState::CreateShaderResourceBinding()):
      m_pPSO->CreateShaderResourceBinding(&m_pSRB); Note that an SRB is only compatible with the pipeline state it was created from. SRB object inherits all static bindings from shaders in the pipeline, but is not allowed to change them.
      Mutable resources can only be set once for every instance of a shader resource binding. Such resources are intended to define specific material properties. For instance, a diffuse texture for a specific material is not expected to change once the material is defined and can be set right after the SRB object has been created:
      m_pSRB->GetVariable(SHADER_TYPE_PIXEL, "tex2DDiffuse")->Set(pDiffuseTexSRV); In some cases it is necessary to bind a new resource to a variable every time a draw command is invoked. Such variables should be labeled as dynamic, which will allow setting them multiple times through the same SRB object:
      m_pSRB->GetVariable(SHADER_TYPE_VERTEX, "cbRandomAttribs")->Set(pRandomAttrsCB); Under the hood, the engine pre-allocates descriptor tables for static and mutable resources when an SRB objcet is created. Space for dynamic resources is dynamically allocated at run time. Static and mutable resources are thus more efficient and should be used whenever possible.
      As you can see, Diligent Engine does not expose low-level details of how resources are bound to shader variables. One reason for this is that these details are very different for various APIs. The other reason is that using low-level binding methods is extremely error-prone: it is very easy to forget to bind some resource, or bind incorrect resource such as bind a buffer to the variable that is in fact a texture, especially during shader development when everything changes fast. Diligent Engine instead relies on shader reflection system to automatically query the list of all shader variables. Grouping variables based on three types mentioned above allows the engine to create optimized layout and take heavy lifting of matching resources to API-specific resource location, register or descriptor in the table.
      This post gives more details about the resource binding model in Diligent Engine.
      Setting the Pipeline State and Committing Shader Resources
      Before any draw or compute command can be invoked, the pipeline state needs to be bound to the context:
      m_pContext->SetPipelineState(m_pPSO); Under the hood, the engine sets the internal PSO object in the command list or calls all the required native API functions to properly configure all pipeline stages.
      The next step is to bind all required shader resources to the GPU pipeline, which is accomplished by IDeviceContext::CommitShaderResources() method:
      m_pContext->CommitShaderResources(m_pSRB, COMMIT_SHADER_RESOURCES_FLAG_TRANSITION_RESOURCES); The method takes a pointer to the shader resource binding object and makes all resources the object holds available for the shaders. In the case of D3D12, this only requires setting appropriate descriptor tables in the command list. For older APIs, this typically requires setting all resources individually.
      Next-generation APIs require the application to track the state of every resource and explicitly inform the system about all state transitions. For instance, if a texture was used as render target before, while the next draw command is going to use it as shader resource, a transition barrier needs to be executed. Diligent Engine does the heavy lifting of state tracking.  When CommitShaderResources() method is called with COMMIT_SHADER_RESOURCES_FLAG_TRANSITION_RESOURCES flag, the engine commits and transitions resources to correct states at the same time. Note that transitioning resources does introduce some overhead. The engine tracks state of every resource and it will not issue the barrier if the state is already correct. But checking resource state is an overhead that can sometimes be avoided. The engine provides IDeviceContext::TransitionShaderResources() method that only transitions resources:
      m_pContext->TransitionShaderResources(m_pPSO, m_pSRB); In some scenarios it is more efficient to transition resources once and then only commit them.
      Invoking Draw Command
      The final step is to set states that are not part of the PSO, such as render targets, vertex and index buffers. Diligent Engine uses Direct3D11-syle API that is translated to other native API calls under the hood:
      ITextureView *pRTVs[] = {m_pRTV}; m_pContext->SetRenderTargets(_countof( pRTVs ), pRTVs, m_pDSV); // Clear render target and depth buffer const float zero[4] = {0, 0, 0, 0}; m_pContext->ClearRenderTarget(nullptr, zero); m_pContext->ClearDepthStencil(nullptr, CLEAR_DEPTH_FLAG, 1.f); // 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); Different native APIs use various set of function to execute draw commands depending on command details (if the command is indexed, instanced or both, what offsets in the source buffers are used etc.). For instance, there are 5 draw commands in Direct3D11 and more than 9 commands in OpenGL with something like glDrawElementsInstancedBaseVertexBaseInstance not uncommon. Diligent Engine hides all details with single IDeviceContext::Draw() method that takes 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); For compute commands, there is IDeviceContext::DispatchCompute() method that takes DispatchComputeAttribs structure that defines compute grid dimension.
      Source Code
      Full engine source code is available on GitHub and is free to use. The repository contains tutorials, sample applications, asteroids performance benchmark and an example Unity project that uses Diligent Engine in native plugin.
      Atmospheric scattering sample demonstrates how Diligent Engine can be used to implement various rendering tasks: loading textures from files, using complex shaders, rendering to multiple render targets, using compute shaders and unordered access views, etc.

      Asteroids performance benchmark is based on this demo developed by Intel. It renders 50,000 unique textured asteroids and allows comparing performance of Direct3D11 and Direct3D12 implementations. Every asteroid is a combination of one of 1000 unique meshes and one of 10 unique textures.

      Finally, there is an example project that shows how Diligent Engine can be integrated with Unity.

      Future Work
      The engine is under active development. It currently supports Windows desktop, Universal Windows, Linux, Android, MacOS, and iOS platforms. Direct3D11, Direct3D12, OpenGL/GLES backends are now feature complete. Vulkan backend is coming next, and Metal backend is in the plan.
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