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OpenGL To transition to OpenGL 3.2

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Hi, my question is basically: How do I move to 3.2 core profile from before using and mostly understanding the Nehe tutorials? The projects I've previously written have been based on the Nehe tutorials and now that I feel kind of comfortable with that code I thought that moving to more modern code would be a good thing. However I'm getting stumped all around when I try to find tutorials, guides or whatever that explains how to set up a 3.2 context (the highest version supported by my graphics card). Are there any great tutorials out there on this? Or, rather, how should I start? I'm lost again :) Thanks, Marcus Axelsson (goes back to reading the specification with a worried expression)

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I have been learning OpenGL 3.2 core profile for about a month. There are some tutorials which are very useful. For example,

http://www.opengl.org/wiki/Category:Tutorials
http://sites.google.com/site/opengltutorialsbyaks/introduction-to-opengl-3-2---tutorial-01
http://nopper.tv/opengl_3_2.html
http://www.g-truc.net/post-0204.html

By reading these materials, it is easy to set up my first demo with phong lighting and texture mapping.

However, the most troublesome problem for me is the immature support by related development libraries. Especially, the GUI libraries like freeglut, SDL and QT, are still far away from stable support for core profile. I have post some threads in this forum to show the bugs of freeglut and no solution could be received. I hope all the problems could be solved as soon as possible.

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I've checked out two of those links (the sample program links) before and they're OK. I hope to understand them better after having read through the specification. The other two links seem allright. I'll have a close look at those.

The libraries you mention will probably have support soon enough. Or maybe they're working on 4.0 compatible code instead? It'd be great with some 3 compatible stuff though, since I'm not really in a position to buy a new graphics card right now :)

Thanks for the links.

Anyone else got something? All references and guides, tutorials and code samples are welcome.

Thanks,
Marcus Axelsson

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Original post by ZHAO Peng
Especially, the GUI libraries like freeglut, SDL and QT, are still far away from stable support for core profile.
It is even worse, not even the most basic libraries like GLEW and GLee do, which is ironical since they explicitely claim to support all the new versions and extensions. Nevertheless, both libraries use the 1.x mechanism for querying extensions. Which, in principle is fine, since the 3.x way totally sucks (especially if you want support both 1.x/2.x and 3.x codepaths), whereas the 1.x way works perfectly well.

However, the 1.x extension query mechanism is deprecated for 3.0 and removed from 3.1, and it is indeed unimplemented (or rather, disabled -- returns null) on recent drivers. I've even had that happen on a compatibility profile (where it's supposed to work!) on a nVidia development driver not long ago, though that was probably a driver bug.
Sadly, the Khronos group seems to have put a lot of effort into making migrating to OpenGL 3.x while retaining a legacy path as troublesome as possible (GLSL versions being another such thing), you have to wonder why. Probably the plan behind that is something like "move on, no way back".

In reply to the OP:
You must use either wglCreateContextAttribsARB or the glx counterpart, depending on whether you're under Windows or Unix.
These functions take a zero-terminated list of name-value integer pairs. Upon first sight, this may be confusing, but once you get it, it is actually quite nice, flexible, and easy. Don't forget the zero at the end!
Also, do note that you must create a fake context first to get the function pointer to that function. You cannot just call the function like that.
The links posted by ZHAO Peng show how to do this.

Also, you must use glGetStringi instead of glGetString to query for extensions. This involves many more driver calls than "the old way" did, and it makes caching the info a lot more tedious too, but alas... that's how it is. If you structure your program properly so all caps are queried at startup and stored in a few global variables, it doesn't make a real difference at runtime, though it might take half a second longer to start up.
Actually, to be correct, you must get a function pointer for glGetStringi, too, since it is not a OpenGL 1.3 function (only implemented after 3.0). Strange enough, it does work either way on my system, so it seems that glGetStringi actually has an entry in the GL import library. I don't think that this is technically correct.

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Sorry! After lots of tries, I should admit that the core profile support of freeglut is not so bad. The problems I met are caused by GLEW. "glewExperimental" should be set to "GL_TRUE" for the drivers NVIDIA-Linux-x86_64-190.53 and NVIDIA-Linux-x86_64-195.36.07.04.

God! I have wasted several days for this "trap".

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Quote:
Original post by ZHAO Peng
Sorry! After lots of tries, I should admit that the core profile support of freeglut is not so bad. The problems I met are caused by GLEW. "glewExperimental" should be set to "GL_TRUE" for the drivers NVIDIA-Linux-x86_64-190.53 and NVIDIA-Linux-x86_64-195.36.07.04.
God! I have wasted several days for this "trap".

I've not tried it yet but someone's written a OpenGL 3/4 core profile extractor (see here). It looks a bit like a GLEW for core profiles.

Looks like it might be useful if your IDE does function name completion and you don't want it to keep suggesting deprecated functions.

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Quote:
Original post by dave j
Quote:
Original post by ZHAO Peng
Sorry! After lots of tries, I should admit that the core profile support of freeglut is not so bad. The problems I met are caused by GLEW. "glewExperimental" should be set to "GL_TRUE" for the drivers NVIDIA-Linux-x86_64-190.53 and NVIDIA-Linux-x86_64-195.36.07.04.
God! I have wasted several days for this "trap".

I've not tried it yet but someone's written a OpenGL 3/4 core profile extractor (see here). It looks a bit like a GLEW for core profiles.

Looks like it might be useful if your IDE does function name completion and you don't want it to keep suggesting deprecated functions.


Yes, GL3W looks a new and easy use library which is similar to GLEW. It's good news for programmers to have one more choice. Thanks!

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Hm. gl3w seemed really useful. But I can't run the script at all. I get an "invalid syntax" error when I try to run it (python.exe "gl3w.py"). So... too bad :/

With GLUT and this gl3w I think it'd be a breeze to get the ogl 3.2 context up and running. Which would be great :)

Thanks for keeping the thread alive, guys.

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Original post by tre
Hm. gl3w seemed really useful. But I can't run the script at all. I get an "invalid syntax" error when I try to run it (python.exe "gl3w.py"). So... too bad :/

With GLUT and this gl3w I think it'd be a breeze to get the ogl 3.2 context up and running. Which would be great :)

Thanks for keeping the thread alive, guys.

Which version of Python are you using? The script is for 2.6.

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Allright. Got that going. Now to getting a project on :)

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I have to be honest, I'm about to give up on all of this.
I'm still counting myself as a beginner and I've been focused on getting OpenGL functioning correctly for me. I've got a small program up and running in the old context. I've got shaders creating "nightlights" on a globe which the user can rotate around.
Now I'm supposed to go from this to the new context and nothing will work. There are no decent tutorials out there at all. I've searched, believe me.
There are sample programs but they are very, very, very lacking in comment or explaining text.

I do not want to have it all laid out in front of me, but man, this is ridiculous!
I can get an OGL 3.2 context going. I did actually. But when I got the context going I found out that I can't do... well... anything. Since everything I've been learning for the past one and a half years is now deprecated code.

Previously I've used the NeHe tutorials to get me going and understanding OGL and Windows programming and that went so well that I finally could stand on my own wobbly legs. Now that the context has changed, and not only from 3.x but to 4.0 (which I can't program for), there is nothing I can read and understand. I've never used GLUT before but used NeHe's code for creating a window and the OGL context. But now I've found myself using GLUT instead, which I'm not really comfortable with. It feels strange. Is it really this easy to use (create a couple of display/reshape/input functions, glutSwapBuffers and then compile)? Or am I missing something? Because it feels like I'm skipping most of the programming I've been doing the last year.

And more questions. What the H is GLUS? The Python script gave me a OGL3.2 context but now what? How do I proceed? What has substituted GL_MATRIXMODE and GL_PROJECTION? And why? Setting up shaders with GLUT? My god, I can't even figure out why the keyboard won't react to the "r" button on my keyboard (or turns my cube turqoise) with the keyboardfunc in GLUT.

You see, it's quite a bit to catch up on. What I'm seriously considering is if it's really worth the trouble.

Input, please. I'm not really ready to quit my game programming aspirations just yet, but it's such a daunting task right now. Everything is new, and I have nothing to go by. I'm sort of fumbling in the dark here.

Sorry if this comes off as a crazed rant. I'm sure OGL is still as powerful (or more powerful) than ever before. It just took a turn for the worse for me. Too many changes, too soon.
The specifications aren't really helping me much. Just feels like Khronos is saying "we're so great since OGL can do this and this now and by the way 90 percent of what you've learnt is now pure crap". And then a list over deprecated functions. So I'm not really too hot for the specification just yet (however, note that I've not read all of it yet).

I'm frustrated and this became too long. Sorry for that.

What I'm really hoping for is some guidance, really.

All the best,
Marcus Axelsson

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If it's too hard, try learning OpenGL 2.0 first, then shaders, and then, you'll be ready to use OpenGL 3.2 without problems.

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Original post by HuntsMan
If it's too hard, try learning OpenGL 2.0 first, then shaders, and then, you'll be ready to use OpenGL 3.2 without problems.


Thanks for your reply.
I thought I had a grip on 2.0 though, but maybe not. I've allready written some shaders. Maybe it's not enough.
Thanks again. I'll go back to 2.0 and hack on through that one.

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Original post by tre
I have to be honest, I'm about to give up on all of this.
I'm still counting myself as a beginner and I've been focused on getting OpenGL functioning correctly for me. I've got a small program up and running in the old context. I've got shaders creating "nightlights" on a globe which the user can rotate around.
Now I'm supposed to go from this to the new context and nothing will work. There are no decent tutorials out there at all. I've searched, believe me.
There are sample programs but they are very, very, very lacking in comment or explaining text.


Yes, I agree with you about the tutorials and samples. However, it is not very hard to read the sample codes and find the explain on the wiki (like VBO, VAO, UBO...).

Quote:
Original post by tre
I do not want to have it all laid out in front of me, but man, this is ridiculous!
I can get an OGL 3.2 context going. I did actually. But when I got the context going I found out that I can't do... well... anything. Since everything I've been learning for the past one and a half years is now deprecated code.
Previously I've used the NeHe tutorials to get me going and understanding OGL and Windows programming and that went so well that I finally could stand on my own wobbly legs. Now that the context has changed, and not only from 3.x but to 4.0 (which I can't program for), there is nothing I can read and understand. I've never used GLUT before but used NeHe's code for creating a window and the OGL context. But now I've found myself using GLUT instead, which I'm not really comfortable with. It feels strange. Is it really this easy to use (create a couple of display/reshape/input functions, glutSwapBuffers and then compile)? Or am I missing something? Because it feels like I'm skipping most of the programming I've been doing the last year.

And more questions. What the H is GLUS? The Python script gave me a OGL3.2 context but now what? How do I proceed? What has substituted GL_MATRIXMODE and GL_PROJECTION? And why? Setting up shaders with GLUT? My god, I can't even figure out why the keyboard won't react to the "r" button on my keyboard (or turns my cube turqoise) with the keyboardfunc in GLUT.


I have learned the OpenGL core profile for several weeks. I use freeglut (codes from SVN), GLEW 1.5.4, GLM 0.9Beta2 on OpenSUSE 11.2 with Nvidia GTX260. After some hard work, everything is OK. It is necessary to call "glutInitContextVersion(3,3); glutInitContextProfile(GLUT_CORE_PROFILE);" and " glewExperimental= GL_TRUE;
GLenum err = glewInit();". This can make sure that freeglut and GLEW could work properly.

GL_MATRIXMODE and GL_PROJECTION have been removed from core profile. Firstly, uniform variables for model view matrix and projection matrix should be declared in vertex shader.Then we can compute the matrices using GLM which is really simple in the host application and set the values using glUniformMatrix4fv. You can find these codes in most samples.
The keyboard function should work well in freeglut. I am not sure what is your problem.


Quote:
Original post by tre
You see, it's quite a bit to catch up on. What I'm seriously considering is if it's really worth the trouble.

Input, please. I'm not really ready to quit my game programming aspirations just yet, but it's such a daunting task right now. Everything is new, and I have nothing to go by. I'm sort of fumbling in the dark here.

Sorry if this comes off as a crazed rant. I'm sure OGL is still as powerful (or more powerful) than ever before. It just took a turn for the worse for me. Too many changes, too soon.
The specifications aren't really helping me much. Just feels like Khronos is saying "we're so great since OGL can do this and this now and by the way 90 percent of what you've learnt is now pure crap". And then a list over deprecated functions. So I'm not really too hot for the specification just yet (however, note that I've not read all of it yet).


Although it is painful to forget the old functions and experiences, we have to go ahead to the future. Modern OpenGL pipeline is more flexible and powerful. I think it is worth working hard at it.


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First off I'd like to ask forgiveness for the above post that I made. I got very, very frustrated and when I do I usually rant. However my point is still in there and very much alive: Why would anyone, no matter how much better it is with this new way of doing things, in their right mind change it all and then not give simple code with enough comments so that anyone who's been using OGL < 3.x could understand it? It is a very strange way of doing things, this. Changing it this much and then not provide enough information so that people are left spending hours, days, months to get it working.


Quote:
Original post by ZHAO Peng
Yes, I agree with you about the tutorials and samples. However, it is not very hard to read the sample codes and find the explain on the wiki (like VBO, VAO, UBO...).

I guess I got very frustrated. The sample code I've downloaded (nopper and the rest) run stuff I can't find information on. Say Nopper, those code samples run something called GLUS and I can't find documentation on it anywhere. Very strange.

Quote:
Original post by ZHAO Peng
I have learned the OpenGL core profile for several weeks. I use freeglut (codes from SVN), GLEW 1.5.4, GLM 0.9Beta2 on OpenSUSE 11.2 with Nvidia GTX260. After some hard work, everything is OK. It is necessary to call "glutInitContextVersion(3,3); glutInitContextProfile(GLUT_CORE_PROFILE);" and " glewExperimental= GL_TRUE;
GLenum err = glewInit();". This can make sure that freeglut and GLEW could work properly.

GL_MATRIXMODE and GL_PROJECTION have been removed from core profile. Firstly, uniform variables for model view matrix and projection matrix should be declared in vertex shader.Then we can compute the matrices using GLM which is really simple in the host application and set the values using glUniformMatrix4fv. You can find these codes in most samples.
The keyboard function should work well in freeglut. I am not sure what is your problem.

I'm trying to get this working with GLUT / FreeGLUT, GLEW in Vista x64 on a 8800GTX.
Where can I find documentation on FreeGLUT, then? How should I know that I need to run the InitContext and ContextProfile? And what does glewExperimental do? When I try to find information on that on google I just end up confused. Why is it necessary for OpenGL 3.x?
So when I've created an OGL 3.2 context I should create a shader pair, just the normal "here's the vertex" and "this is the fragment color" shaders? Or is it more advanced? What do I need to do at this point?
I've downloaded GLM now and I've been reading about it a bit. So setting the "position values" in main.cpp and sending them to a shader with a uniform would be allright?
Never mind the keyboard function, that's just got to be a part of my rant yesterday :)

Quote:
Original post by ZHAO Peng
Although it is painful to forget the old functions and experiences, we have to go ahead to the future. Modern OpenGL pipeline is more flexible and powerful. I think it is worth working hard at it.

I know. I want to move forward but can't seem to get a grip around how to walk. It's frustrating for me, but I'm going to move forward (or die trying it seems like). The new pipeline does look more flexible and powerful, but as an aspiring developer I don't want to see the GL shrouded in fog and difficulties. It should be open and clear. It doesn't have to be easy, but the more difficult something is, the better commented and documented it has to be. It would've made everything much easier.
I will keep trying to get this to work and try to be a part of the future.

Thanks for taking the time and answering my very long rant that I'm a bit embarrassed about today :)

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Original post by tre
First off I'd like to ask forgiveness for the above post that I made. I got very, very frustrated and when I do I usually rant. However my point is still in there and very much alive: Why would anyone, no matter how much better it is with this new way of doing things, in their right mind change it all and then not give simple code with enough comments so that anyone who's been using OGL < 3.x could understand it? It is a very strange way of doing things, this. Changing it this much and then not provide enough information so that people are left spending hours, days, months to get it working.

Actually, I also felt painful to meet so many new concepts and techniques like VBO, VAO,UBO...
After reading some materials, I have got initial understanding about them. The red book has been updated to the version 7 which covers OpenGL 3.0&3.1. If you could get one, it should be very useful. The books and other materials for OpenGL 3.2 or later should be published in the future. However, programmers could not wait so long. Sometimes learning these new techniques is like an adventure which could make me excited.

Quote:

Say Nopper, those code samples run something called GLUS and I can't find documentation on it anywhere. Very strange.

GLUS is just a very preliminary library written by Nopper for his OpenGL 3.2 samples. It is lack of many indispensable functions. It is not fair to ask him to build a great libary for us in a short time.:) Maybe it will become more mature. However, libraries like freeglut and qt should be used currently.

Quote:

Where can I find documentation on FreeGLUT, then? How should I know that I need to run the InitContext and ContextProfile? And what does glewExperimental do? When I try to find information on that on google I just end up confused. Why is it necessary for OpenGL 3.x?

In fact, I don't read the document of freeglut because most of the functions don't change. When move to the OpenGL3.2, I know it introduces the profile mechanism. So I search in the head file and find glutInitContextVersion and glutInitContextProfile. glewExperimental really upset me. When I use core profile, some functions could not be got by GLEW. I wasted several days for this problem. Finally I found glewExperimental=GL_TRUE in Nopper's samples. You can find the detail on the website of GLEW.

Quote:

I've downloaded GLM now and I've been reading about it a bit. So setting the "position values" in main.cpp and sending them to a shader with a uniform would be allright?

Yes, just compute the transform matrixes using GLM and send them to shader. In the vertex shader, vertex coordinates should be multiplied by these matrixes.

Quote:

The new pipeline does look more flexible and powerful, but as an aspiring developer I don't want to see the GL shrouded in fog and difficulties. It should be open and clear. It doesn't have to be easy, but the more difficult something is, the better commented and documented it has to be. It would've made everything much easier.

Maybe Khronos are too busy and other evolved companies don't want to put their effort into it. The only way is to wait for the books and better tutorials. But for me it is too slow.
Come on! Good luck!

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First off, thanks Zhao for your replies. They give me hope as well as helping me move forward.

I've decided to go with a 50/50 approach to this, that is OpenGL 2.0 but I'll be leaning heavily on GLSL. Using this approach I should be able to get on better terms with both GLSL and VAO, VBO and whatever other abbreviations I need to learn. A good approach? Thoughts?

I'm also thinking of buying some more books. I've got the "OpenGL Game Programming" and "More OpenGL game programming" books. The new books I'm thinking of buying is "Beginning C++ Game Programming" and the "Orange Book 3rd Edition".
The "beginning"-book should prove useful however I decide to move forwards, but how is the 3rd edition of the orange book? Is it close to what I'll be doing in 3.2 and 4.0? I have found some information on it - that it's written with 3.1 in mind. How much does 3.1, 3.2 and 4.0 differ from each other?
Mainly, will I have to buy the fourth edition of the orange book just to get started in the programmable pipeline?

Thanks for taking the time.
Marcus Axelsson

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Quote:
Original post by tre
First off, thanks Zhao for your replies. They give me hope as well as helping me move forward.

You are welcome. I am also happy to have a companion on the road to modern OpenGL.

Quote:

I've decided to go with a 50/50 approach to this, that is OpenGL 2.0 but I'll be leaning heavily on GLSL. Using this approach I should be able to get on better terms with both GLSL and VAO, VBO and whatever other abbreviations I need to learn. A good approach? Thoughts?


If you don't want to learn core profile purely, compatibility profile of OpenGL 3.2 or later should be good choice. It contains all the features of 2.0 and other more advanced functions.

Quote:

I'm also thinking of buying some more books. I've got the "OpenGL Game Programming" and "More OpenGL game programming" books. The new books I'm thinking of buying is "Beginning C++ Game Programming" and the "Orange Book 3rd Edition".
The "beginning"-book should prove useful however I decide to move forwards, but how is the 3rd edition of the orange book? Is it close to what I'll be doing in 3.2 and 4.0? I have found some information on it - that it's written with 3.1 in mind. How much does 3.1, 3.2 and 4.0 differ from each other?
Mainly, will I have to buy the fourth edition of the orange book just to get started in the programmable pipeline?


I am not familiar with the books of game programming. For the orange book, I think it is not very necessary when I looked through the first edition. It has too many pages. For programmers who are good at c or cplusplus, it is not hard to learn GLSL by reading the specification because the grammar is very similar. Maybe what we need is the application examples. If the third edition has good examples and application informations, it should be useful.

Good luck.

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One other suggestion is to learn OpenGL ES 2.0: it is very similar to OpenGL 3.0 core profile and there are plenty of resources out there for learning from.

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Original post by ZHAO Peng
If you don't want to learn core profile purely, compatibility profile of OpenGL 3.2 or later should be good choice. It contains all the features of 2.0 and other more advanced functions.


Didn't even think of the compability profile. Great idea.

And yeah, I agree. Modern application examples, thoroughly commented and documented would be the single best thing when it comes to learning GLSL. Well, save from school.

I want to lean the core profile, but I think I have too much other stuff to learn before I can dive into it. I'll be taking the long road instead, learning the things that are important for the core profile. I'll probably start up a couple of core profile projects just to see if I'm ready to move on yet or if I need to read even more.

I'll probably see if I can get my hands on the Orange Book since it at least covers GLSL which I could need. The C++ Game programming book seems like a great book for learning game logic and such. I'm on the hunt for more great books. I need more places to jump off from, so to speak.

Thanks again,
Marcus Axelsson

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Quote:
Original post by Bregma
One other suggestion is to learn OpenGL ES 2.0: it is very similar to OpenGL 3.0 core profile and there are plenty of resources out there for learning from.


I will probably stick with OpenGL 3.2 compability profile for now. But thanks for the tip. I'll keep it in mind.

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      The approach taken in the engine does not limit scalability as the application is expected to create one deferred context per thread, and internally every deferred context records a command list in lock-free fashion. At the same time this approach maps well to older APIs.
      In current implementation, only one immediate context that uses default graphics command queue is created. To support multiple GPUs or multiple command queue types (compute, copy, etc.), it is natural to have one immediate contexts per queue. Cross-context synchronization utilities will be necessary.
      Swap Chain (ISwapChain interface). Swap chain interface represents a chain of back buffers and is responsible for showing the final rendered image on the screen.
      Render device, device contexts and swap chain are created during the engine initialization.
      Resources (ITexture and IBuffer interfaces). There are two types of resources - textures and buffers. There are many different texture types (2D textures, 3D textures, texture array, cubmepas, etc.) that can all be represented by ITexture interface.
      Resources Views (ITextureView and IBufferView interfaces). While textures and buffers are mere data containers, texture views and buffer views describe how the data should be interpreted. For instance, a 2D texture can be used as a render target for rendering commands or as a shader resource.
      Pipeline State (IPipelineState interface). GPU pipeline contains many configurable stages (depth-stencil, rasterizer and blend states, different shader stage, etc.). Direct3D11 uses coarse-grain objects to set all stage parameters at once (for instance, a rasterizer object encompasses all rasterizer attributes), while OpenGL contains myriad functions to fine-grain control every individual attribute of every stage. Both methods do not map very well to modern graphics hardware that combines all states into one monolithic state under the hood. Direct3D12 directly exposes pipeline state object in the API, and Diligent Engine uses the same approach.
      Shader Resource Binding (IShaderResourceBinding interface). Shaders are programs that run on the GPU. Shaders may access various resources (textures and buffers), and setting correspondence between shader variables and actual resources is called resource binding. Resource binding implementation varies considerably between different API. Diligent Engine introduces a new object called shader resource binding that encompasses all resources needed by all shaders in a certain pipeline state.
      API Basics
      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. Graphics APIs usually have a native object that represents linear buffer. Diligent Engine uses IBuffer interface as an abstraction for a native buffer. To create a buffer, one needs to populate BufferDesc structure and call IRenderDevice::CreateBuffer() method as in the following example:
      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 ); While there is usually just one buffer object, different APIs use very different approaches to represent textures. For instance, in Direct3D11, there are ID3D11Texture1D, ID3D11Texture2D, and ID3D11Texture3D objects. In OpenGL, there is individual object for every texture dimension (1D, 2D, 3D, Cube), which may be a texture array, which may also be multisampled (i.e. GL_TEXTURE_2D_MULTISAMPLE_ARRAY). As a result there are nine different GL texture types that Diligent Engine may create under the hood. In Direct3D12, there is only one resource interface. Diligent Engine hides all these details in ITexture interface. There is only one  IRenderDevice::CreateTexture() method that is capable of creating all texture types. Dimension, format, array size and all other parameters are specified by the members of the TextureDesc structure:
      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 ); If native API supports multithreaded resource creation, textures and buffers can be created by multiple threads simultaneously.
      Interoperability with native API provides access to the native buffer/texture objects and also allows creating Diligent Engine objects from native handles. It allows applications seamlessly integrate native API-specific code with Diligent Engine.
      Next-generation APIs allow fine level-control over how resources are allocated. Diligent Engine does not currently expose this functionality, but it can be added by implementing IResourceAllocator interface that encapsulates specifics of resource allocation and providing this interface to CreateBuffer() or CreateTexture() methods. If null is provided, default allocator should be used.
      Initializing the Pipeline State
      As it was mentioned earlier, Diligent Engine follows next-gen APIs 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.). This approach maps directly to Direct3D12/Vulkan, but is also beneficial for older APIs as it eliminates pipeline misconfiguration errors. With many individual calls tweaking various GPU pipeline settings it is very easy to forget to set one of the states or assume the stage is already properly configured when in fact it is not. Using pipeline state object helps avoid these problems as all stages are configured at once.
      Creating Shaders
      While in earlier APIs shaders were bound separately, in the next-generation APIs as well as in Diligent Engine shaders are part of the pipeline state object. The biggest challenge when authoring shaders is that Direct3D and OpenGL/Vulkan use different shader languages (while Apple uses yet another language in their Metal API). Maintaining two versions of every shader is not an option for real applications and Diligent Engine implements shader source code converter that allows shaders authored in HLSL to be translated to GLSL. To create a shader, one needs to populate ShaderCreationAttribs structure. SourceLanguage member of this structure tells the system which language the shader is authored in:
      SHADER_SOURCE_LANGUAGE_DEFAULT - The shader source language matches the underlying graphics API: HLSL for Direct3D11/Direct3D12 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. SHADER_SOURCE_LANGUAGE_GLSL - The shader source is in GLSL. There is currently no GLSL to HLSL converter, so this value should only be used for OpenGL and OpenGLES modes. There are two ways to provide the shader source code. The first way is to use Source member. The second way is to provide a file path in FilePath member. Since the engine is entirely decoupled from the platform and the host file system is platform-dependent, the structure exposes pShaderSourceStreamFactory member that is intended to provide the engine access to the file system. If FilePath is provided, shader source factory must also be provided. If the shader source contains any #include directives, the source stream factory will also be used to load these files. The engine provides default implementation for every supported platform that should be sufficient in most cases. Custom implementation can be provided when needed.
      When sampling a texture in a shader, the texture sampler was traditionally specified as separate object that was bound to the pipeline at run time or set as part of the texture object itself. However, in most cases it is known beforehand what kind of sampler will be used in the shader. Next-generation APIs expose new type of sampler called static sampler that can be initialized directly in the pipeline state. Diligent Engine exposes this functionality: when creating a shader, textures can be assigned static samplers. If static sampler is assigned, it will always be used instead of the one initialized in the texture shader resource view. To initialize static samplers, prepare an array of StaticSamplerDesc structures and initialize StaticSamplers and NumStaticSamplers members. Static samplers are more efficient and it is highly recommended to use them whenever possible. On older APIs, static samplers are emulated via generic sampler objects.
      The following is an example of shader initialization:
      ShaderCreationAttribs Attrs; Attrs.Desc.Name = "MyPixelShader"; Attrs.FilePath = "MyShaderFile.fx"; Attrs.SearchDirectories = "shaders;shaders\\inc;"; Attrs.EntryPoint = "MyPixelShader"; Attrs.Desc.ShaderType = SHADER_TYPE_PIXEL; Attrs.SourceLanguage = SHADER_SOURCE_LANGUAGE_HLSL; BasicShaderSourceStreamFactory BasicSSSFactory(Attrs.SearchDirectories); Attrs.pShaderSourceStreamFactory = &BasicSSSFactory; ShaderVariableDesc ShaderVars[] = {     {"g_StaticTexture", SHADER_VARIABLE_TYPE_STATIC},     {"g_MutableTexture", SHADER_VARIABLE_TYPE_MUTABLE},     {"g_DynamicTexture", SHADER_VARIABLE_TYPE_DYNAMIC} }; Attrs.Desc.VariableDesc = ShaderVars; Attrs.Desc.NumVariables = _countof(ShaderVars); Attrs.Desc.DefaultVariableType = SHADER_VARIABLE_TYPE_STATIC; StaticSamplerDesc StaticSampler; StaticSampler.Desc.MinFilter = FILTER_TYPE_LINEAR; StaticSampler.Desc.MagFilter = FILTER_TYPE_LINEAR; StaticSampler.Desc.MipFilter = FILTER_TYPE_LINEAR; StaticSampler.TextureName = "g_MutableTexture"; Attrs.Desc.NumStaticSamplers = 1; Attrs.Desc.StaticSamplers = &StaticSampler; ShaderMacroHelper Macros; Macros.AddShaderMacro("USE_SHADOWS", 1); Macros.AddShaderMacro("NUM_SHADOW_SAMPLES", 4); Macros.Finalize(); Attrs.Macros = Macros; RefCntAutoPtr<IShader> pShader; m_pDevice->CreateShader( Attrs, &pShader );
      Creating the Pipeline State Object
      After all required shaders are created, the rest of the fields of the PipelineStateDesc structure provide depth-stencil, rasterizer, and blend state descriptions, the number and format of render targets, input layout format, etc. For instance, rasterizer state can be described as follows:
      PipelineStateDesc PSODesc; RasterizerStateDesc &RasterizerDesc = PSODesc.GraphicsPipeline.RasterizerDesc; RasterizerDesc.FillMode = FILL_MODE_SOLID; RasterizerDesc.CullMode = CULL_MODE_NONE; RasterizerDesc.FrontCounterClockwise = True; RasterizerDesc.ScissorEnable = True; RasterizerDesc.AntialiasedLineEnable = False; Depth-stencil and blend states are defined in a similar fashion.
      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.
    • By LifeArtist
      Good Evening,
      I want to make a 2D game which involves displaying some debug information. Especially for collision, enemy sights and so on ...
      First of I was thinking about all those shapes which I need will need for debugging purposes: circles, rectangles, lines, polygons.
      I am really stucked right now because of the fundamental question:
      Where do I store my vertices positions for each line (object)? Currently I am not using a model matrix because I am using orthographic projection and set the final position within the VBO. That means that if I add a new line I would have to expand the "points" array and re-upload (recall glBufferData) it every time. The other method would be to use a model matrix and a fixed vbo for a line but it would be also messy to exactly create a line from (0,0) to (100,20) calculating the rotation and scale to make it fit.
      If I proceed with option 1 "updating the array each frame" I was thinking of having 4 draw calls every frame for the lines vao, polygons vao and so on. 
      In addition to that I am planning to use some sort of ECS based architecture. So the other question would be:
      Should I treat those debug objects as entities/components?
      For me it would make sense to treat them as entities but that's creates a new issue with the previous array approach because it would have for example a transform and render component. A special render component for debug objects (no texture etc) ... For me the transform component is also just a matrix but how would I then define a line?
      Treating them as components would'nt be a good idea in my eyes because then I would always need an entity. Well entity is just an id !? So maybe its a component?
      Regards,
      LifeArtist
    • By QQemka
      Hello. I am coding a small thingy in my spare time. All i want to achieve is to load a heightmap (as the lowest possible walking terrain), some static meshes (elements of the environment) and a dynamic character (meaning i can move, collide with heightmap/static meshes and hold a varying item in a hand ). Got a bunch of questions, or rather problems i can't find solution to myself. Nearly all are deal with graphics/gpu, not the coding part. My c++ is on high enough level.
      Let's go:
      Heightmap - i obviously want it to be textured, size is hardcoded to 256x256 squares. I can't have one huge texture stretched over entire terrain cause every pixel would be enormous. Thats why i decided to use 2 specified textures. First will be a tileset consisting of 16 square tiles (u v range from 0 to 0.25 for first tile and so on) and second a 256x256 buffer with 0-15 value representing index of the tile from tileset for every heigtmap square. Problem is, how do i blend the edges nicely and make some computationally cheap changes so its not obvious there are only 16 tiles? Is it possible to generate such terrain with some existing program?
      Collisions - i want to use bounding sphere and aabb. But should i store them for a model or entity instance? Meaning i have 20 same trees spawned using the same tree model, but every entity got its own transformation (position, scale etc). Storing collision component per instance grats faster access + is precalculated and transformed (takes additional memory, but who cares?), so i stick with this, right? What should i do if object is dynamically rotated? The aabb is no longer aligned and calculating per vertex min/max everytime object rotates/scales is pretty expensive, right?
      Drawing aabb - problem similar to above (storing aabb data per instance or model). This time in my opinion per model is enough since every instance also does not have own vertex buffer but uses the shared one (so 20 trees share reference to one tree model). So rendering aabb is about taking the model's aabb, transforming with instance matrix and voila. What about aabb vertex buffer (this is more of a cosmetic question, just curious, bumped onto it in time of writing this). Is it better to make it as 8 points and index buffer (12 lines), or only 2 vertices with min/max x/y/z and having the shaders dynamically generate 6 other vertices and draw the box? Or maybe there should be just ONE 1x1x1 cube box template moved/scaled per entity?
      What if one model got a diffuse texture and a normal map, and other has only diffuse? Should i pass some bool flag to shader with that info, or just assume that my game supports only diffuse maps without fancy stuff?
      There were several more but i forgot/solved them at time of writing
      Thanks in advance
    • By RenanRR
      Hi All,
      I'm reading the tutorials from learnOpengl site (nice site) and I'm having a question on the camera (https://learnopengl.com/Getting-started/Camera).
      I always saw the camera being manipulated with the lookat, but in tutorial I saw the camera being changed through the MVP arrays, which do not seem to be camera, but rather the scene that changes:
      Vertex Shader:
      #version 330 core layout (location = 0) in vec3 aPos; layout (location = 1) in vec2 aTexCoord; out vec2 TexCoord; uniform mat4 model; uniform mat4 view; uniform mat4 projection; void main() { gl_Position = projection * view * model * vec4(aPos, 1.0f); TexCoord = vec2(aTexCoord.x, aTexCoord.y); } then, the matrix manipulated:
      ..... glm::mat4 projection = glm::perspective(glm::radians(fov), (float)SCR_WIDTH / (float)SCR_HEIGHT, 0.1f, 100.0f); ourShader.setMat4("projection", projection); .... glm::mat4 view = glm::lookAt(cameraPos, cameraPos + cameraFront, cameraUp); ourShader.setMat4("view", view); .... model = glm::rotate(model, glm::radians(angle), glm::vec3(1.0f, 0.3f, 0.5f)); ourShader.setMat4("model", model);  
      So, some doubts:
      - Why use it like that?
      - Is it okay to manipulate the camera that way?
      -in this way, are not the vertex's positions that changes instead of the camera?
      - I need to pass MVP to all shaders of object in my scenes ?
       
      What it seems, is that the camera stands still and the scenery that changes...
      it's right?
       
       
      Thank you
       
    • By dpadam450
      Sampling a floating point texture where the alpha channel holds 4-bytes of packed data into the float. I don't know how to cast the raw memory to treat it as an integer so I can perform bit-shifting operations.

      int rgbValue = int(textureSample.w);//4 bytes of data packed as color
      // algorithm might not be correct and endianness might need switching.
      vec3 extractedData = vec3(  rgbValue & 0xFF000000,  (rgbValue << 8) & 0xFF000000, (rgbValue << 16) & 0xFF000000);
      extractedData /= 255.0f;
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