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OpenGL Looking for authors - submissions closed (Updated 4/27)

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Update (4/27)

I still have a few people to respond to (in particular those who submitted for terrain or particle systems), but submissions are now closed. I got a lot of great responses and only regret that I can't have everyone write. This is going to be an excellent book.

Background

Kevin and I have been working on a book called More OpenGL Game Programming, which is a direct follow-up to Beginning OpenGL Game Programming and an indirect sequel to OpenGL Game Programming. The first part of the book will cover advanced OpenGL topics not covered in our previous books, and the second part will cover (mostly) graphics techniques that are useful to game programmers. The intent is to present the "standard" way of doing fairly common things, rather than introducing new techniques or covering niche topics. We feel that there is a big gap in the books available at this level, and hope that this will be useful to people who have a basic understanding of 3D game development and want to move to the next level.

The Problem

We've been working on this book for almost a year, and haven't been able to find much time to work on it. The problem is that many of the topics we want to cover require that the author either already have pretty extensive knowledge of it, or have at least several weeks free to dedicate to research. When you have more than 20 topics that fall into this category, it becomes pretty daunting. But rather than cancelling the book, or trying to scale back the content, we (or rather, I, since Kevin opted to drop out) decided instead to find (many) additional authors, each of which will cover a single topic (or in some cases, small number of topics), presumably which they already understand fairly well. Rather than have this be a "Gems-style" collection of unrelated articles, however, I have a table of contents that I'd like to follow, and I'll be adding "glue" to make sure all the sections flow together as naturally as possible.

Where you come in

So the point of all of this is that I'm looking for authors. You'll be fully credited for your work, as well as paid (haven't worked out the exact terms yet, but it'll be on the order of $10/page, to be paid once the final draft from you is received). If you're confident in your technical knowledge and skills, but not confident in your writing ability, don't worry; I'll be acting as editor for this, and there will be additional editors as well.

Table of Contents (Updated 4/8)

The following is the table of contents. Any topics listed in italics have either already been written by me or are tentatively spoken for by someone. The ToC is still mostly flexible, so even if you're not planning on contributing, if you think that there are topics that need to be added - or removed - I'd appreciate the feedback. Part I – Advanced OpenGL The purpose of this part of the book is to cover advanced OpenGL topics that weren't covered in the previous books. Chapter 1 – OpenGL Potpourri 1.1 – Vertex Buffer Objects 1.2 – Pixel Buffer Objects 1.3 - Multisampling 1.4 - Occlusion Queries 1.5 – User clip planes 1.6 - Disabling VSync 1.7 – Framebuffer Objects (may be better in the texture mapping chapter under render-to-texture) [b]Chapter 2 – Introduction to Shaders Chapter 3 – Low-level Shaders Covering ARB_vertex_program and ARB_fragment_program, and possibly some of the newer vendor-specific extensions Chapter 4 – The OpenGL Shading Language Covering GLSL Chapter 5 – Advanced Texture Mapping 5.0 – Anisotropic Filtering 5.1 – Compressed textures 5.2 - NPOT textures/texture rectangles 5.3 - Floating point texture formats 5.4 - Bump Mapping 5.5 - Displacement Mapping 5.6 - Parallax Mapping 5.7 - Dynamic Light Mapping 5.8 - Detail Maps 5.9 - Projective Textures 5.10 - Splatting 5.11 - Refraction/the Fresnel effect 5.12 - Render to Texture Part II – The Elements of a Game(?) This section of the book will turn to showing how to do the types of things you'd do in a game using OpenGL Chapter 6 - Special Effects 6.1 – Billboarding 6.2 - Particle Systems 6.2.1 - point sprites 6.3 - Shadows 6.3.1 - Static Shadows 6.3.2 - Projective Shadows 6.3.3 - Shadow Mapping 6.3.4 - Shadow Volumes 6.4 - Volumetric Fog (maybe not necessary, since we already covered fog coordinates in BOGLGP) 6.5 - NPR (mainly just toon shading) 6.6 – Glow 6.7 - Reflections 6.8 - HDR lighting 6.9 – Explosions Chapter 7 – Rendering Nature 7.1 – Skies 7.1.1 – Skyboxes 7.1.2 – Skyplanes 7.1.3 – Skydomes 7.1.4 – Dynamic methods 7.2 – Terrain (probably just going to give an overview of various techniques, but focus on a brute-force method using hardware) 7.2.1 - Geomipmapping 7.2.2 - Chunked LOD 7.2.3 - Hardware based 7.3 - Clouds 7.4 - Fire 7.5 – Water 7.6 – Plants/vegetation? Chapter 8 - Working with 3D Models 8.1 – Static models (.obj?) 8.2 – Keyframe Animation (.md3?) 8.3 – Vertex Skinning (.mdl? .md5?) 8.4 - Summary Include 3ds in there somewhere? Chapter 9 – Game Engine Design Primer? This may be too big a topic to tackle in a single chapter, and we may be better off simply explaining design choices that were made for the game in the final chapter. Chapter 10 - Making a Game: Another Time to Kill (I'll probably just write this after the game is finished) Appendix A – ARB_vertex_program reference Appendix B – ARB_fragment_program reference Appendix C – GLSlang reference Additional chapter ideas: Scene management/Visibility determination? Physics/collision detection? Audio (OpenAL/SDL/fmod)? See below for my comments on the updated ToC

What you'll be writing

Chapters 3, 4, and 9 (if we include it) will pretty much require a single author. Chapter 8 should probably be a single author as well. The rest of the chapters can be split up with different authors for each subtopic. The total length of the book is going to be 400-500 pages. That's about 30 pages per chapter (except for chapters 3 and 4, which will be longer), and about 2-8 pages per topic (depending). Whenever appropriate, you should use figures, screenshots, tables, etc., to make the book more readable.

Demos

Each subtopic should include at least one demo. The demo should be straightforward, clearly illustrating the material presented in your section, while still being relevant to gaming. I'll provide a basic framework that you should use so there is some commonality among all the demos. If the demo needs extensions, it should use GLee. To be consistent with the previous books, the demos should be written using Visual Studio and Win32. However, I'd like to be able to provide SDL versions of all the demos as well.

Deadlines

I'll need to receive the first draft from you no later than the end of June. If any revisions are needed after I review the material, you'll need to submit a final draft by the end of July. This book is not shipping with a CD. Instead, the sample code will be made available via the book's website. So the demos won't be due until the end of August. That said, since you'll be writing at least a little about the demo and probably include a screenshot, you should at least have a working demo before you submit the first draft.

Interested?

If you're interested, please email me with the following: * Which of the above topics you want to cover * A paragraph or two summarizing what you're going to cover related to the topic. * A brief bio of yourself (basically, if I don't know you, I need you to tell me enough to convice me that you know what you're talking about and that you're going to be reliable) * An estimate of how many pages you'll need to cover the topic well. * A description of the demo (or demos) that you'll include. You can choose more than one topic if you want, but don't overcommit yourself. It's going to be very important that everyone does what they say they will do. I anticipate that for at least some of the topics listed above, I'll have more than one interested party. If you know people that may be interested in this, feel free to point them to this thread.

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Well I really hope you don't have to cancel this book I am looking forward to it [although I still am having problems learning with the first book mostly my fault and I use Dev-C++].

Once I have learned everthing I can from the first I would hope to get the second to advance my skills.

Good Luck.

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Thanks to the people who have emailed me so far. I'll get back to you soon.

Because of some questions brought up by a couple of people who emailed me, and because the number of responses I've received was smaller than I expected, I want to make a few additional comments.

In order to write for this, you don't have to be an expert in the topic you're writing about (though if you are, it'll be somewhat easier). All you really need is a basic understanding of the topic and a desire to learn more. For most of the topics I've listed, 3 months is more than enough time to research, experiment, and then write about it. I figure that most people here are already researching and experimenting all the time, so the only additional work would be the writing, which isn't too bad.

For your bio, I don't need you to convince me that you're a guru (nor do I expect it). I just need to feel comfortable that you know where to start, and I need to be confident that if I pick you to cover a topic, you'll come through for me. I don't want to have to scramble to find a replacement in 3 months when you don't come through for me.

I have no doubt that collectively, the members of this forum can write about every topic I've listed, so I hope that some of you take advantage of this opportunity. Besides the compensation, I know from experience that having writing credits on your resume is a big plus. If I have to, I know plenty of people in the industry that I can tap to help finish this book, but I think it'd be a lot better to have it be a product of the GameDev.net OpenGL community.

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I had bought GL game programming. A thing which disappointed me is that the book is basically a collection of stuff taken from the net. I hope this does not happen this time. I also found the book rather weak in general and I rarely check it (just the vertex array section).

By the way, I'm not sure of some chapters.
1.4 - Occlusion Queries: I just wanted to say there has been some discussion on opengl.org's forum about these. Odds are it's difficult to make the m work right and this means building a decent test app could be difficult.
The latency introduced could be a performance hamper and for "demo-like" apps this always happens. It's difficult to explain their usefulness in simple conditions without showing this behaviour.
1.5 – User clip planes: I'm not sure those things are really supported, besides NEAR and FAR. Maybe I'm misunderstanding the functionality.
1.6 - Disabling VSync: this must be little. MSDN is rather self-exaplanatory on this.
Covering ARB_vertex_program and ARB_fragment_program, and possibly some of the newer vendor-specific extensions: I'm also a fan of ARB_vp and ARB_fp but I must admit that 1- "plain" ARB_vp is badly outdated 2- ARB voted against low level programming. While I still thing NV holds >50% of the installed base, I hardly believe there's future for ASM-like things. This chapters could be quickly outdated. Someone would say it's badly outdated even now.
5.2 - NPOT textures/texture rectangles: take my two cents, don't even think about RECT textures. They are a mess. I have support for them and they really blow up the complexity, assuming NV_rect or EXT_rect. If you're speaking of ARB_npot, then there's nothing much to say on that topic as I see it.
6.3.2 - Projective Shadows and 6.3.3 - Shadow Mapping: what's the difference? I hope this is referring to PSMs since everyone can get standard shadow maps in a week of work.

I hope you'll find those two cents useful!

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Thanks for the feedback, Krohm. Anyone else who would like to comment on the topics is welcome to do so, as they're still subject to change.

To respond to some of your comments.

The section on occlusion queries is pretty brief and discusses the potential issues with them.

The section on user clip planes just covers the usage of glClipPlane(), and it's less than a page.

Yes, the section on disabling VSync is also brief. Keep in mind that this book, along with BOGLGP, is intended to provide readers with a solid foundation in OpenGL for game programming. As often as people here and elsewhere ask about VSync, I think it's worth spending a page or so on it.

I definitely understand your arguments about the low level shaders. I wanted to include coverage of them because they are supported on a wider range of hardware than GLSL, and because there is a lot of sample code out there that uses them. The coverage would be as brief as possible, and would stress that the reader should stick to GLSL whenever possible.

NPOT and RECT textures are included for the sake of completeness.

When I say Projective Shadows, I'm referring to the classic projective planar shadow technique. It's included because it's simple and still occasionally useful.

Finally, I just wanted to mention that nothing from the original OGLGP was taken from the net. Everything was written from scratch by Kevin and myself. We of course used reference material (notably the spec and the Red Book), but we intentionally avoided reading any online tutorials to avoid the tendancy to plagiarize. Looking back now, yeah, the original book is pretty week, but I think that BOGLGP is a really strong introduction to OpenGL.

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After reading this, I agree with most you replied in your message.

I also wanted to say my previous message reads a bit "too strong", I guess I should have written more extensive descriptions of what I meant to say. Looks like it hasn't been misunderstood anyway.

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I agree with Dave on the subject of ARB_vertex_program and ARB_fragment_program. I was recently doing a spell of development on a laptop, which didn't support GLSL, and only partially supported the ARB_*_programs. Laptop videocards are a lot less powerfull, and you don't upgrade a laptop as often as a desktop computer.

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I have some demos you can include if you would like them, but I doubt I would have time to contribute any writing. I will probably barely have time to clean up the demos and get them presentable. Collectively the demos illustrate vertex buffer objects, floating point texture formats and render-to-texture, simple HDR lighting, billboarding (CPU and GPU), impostoring, sky domes with atmospheric scattering, terrain (normal ROAM and chunked LOD), and volumetric clouds (using 3 different modeling/rendering techniques). I also have a very simple game engine library based on GameDev's Enginuity series of articles, and I have recently ported some of my old demos over to use it to get rid of any redundant code and clean the rest up. Any shaders used in the demos are written in GLSL.

I only use a few third-party libraries like SDL, libjpeg, and Intel's GLSDK. I wrote the rest of the code and have released it under the BSD license, so you (and your readers) can do pretty much whatever you want with it. All of the project files are for MS Visual Studio 6.0. I've never ported it to any other platform, but given the libraries I'm using, I doubt it will be difficult.

Some of the demos, like the one using ROAM, are very old and use out-dated techniques. Still, you don't have to include the ones you don't like. I've already written articles on some of the demos, like the ROAM and atmospheric scattering demos. I haven't written any articles on the others, and I've retained the publishing rights for the source code of all of them except two (I won't send you those). Send me an email if you're interested in seeing them.

Sean

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Quote:
Original post by Krohm

1.4 - Occlusion Queries: I just wanted to say there has been some discussion on opengl.org's forum about these. Odds are it's difficult to make the m work right and this means building a decent test app could be difficult.
The latency introduced could be a performance hamper and for "demo-like" apps this always happens. It's difficult to explain their usefulness in simple conditions without showing this behaviour.


I just wanted to mention that GPU Gems 2 has a chapter on how to make occlusion queries useful (with the normal disclaimer that it's not useful for all scenes). To minimize the number of queries, you use a space partitioning tree and, of course, use other culling methods first. To avoid latency, you avoid waiting for the answer to come back. You take advantage of frame coherence and plod on ahead using the answers from the previous frame (intelligently), and collect the answers at the end of the frame for the next frame. Check the answers, and if anything changed that requires you to render something you skipped, go back and render it. It's a bit more complicated than that, but that's the basic gist of it.

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Guest Anonymous Poster
Firstly, in which language would demos be written? If C++, would STL and such be allowable? I would guess that binding and fancy function objects should be avoided at least, but std::vector and friends would be nice to simplify code. Also, a standardised vector3f class ( or similar, and perhaps more for quaternions or matricies ) might be useful for example continuity. Just in general, what kinds of assumptions are allowed?

On a more topic-specific note, how much detail is needed? Things like sound or particle systems could be 2 page topics or 200 page ones...

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Sean: Thanks, I'll check out the demos. I'm sure that at least a few of them will fit in.

AP: Yes, the demos will be in C++. Basic STL is fine. My main goal is to have the demo code be easily understandable.

As for the detail level... with a book this size covering this many topics, you obviously can't go into excruciating detail. What I've tried to do in my own writing is provide just enough theory for the reader to have a decent understanding of how things really work, and have the main focus be on practice and application, without focusing on too much on one particular implementation. So, for example, with particle systems, I'd probably discuss what problems they are meant to solve, what attributes they might have, etc., and then discuss some different design choices for implementing them, accompanied by a simple implementation that can be extended by the reader.

Btw, I'll post an update later about which topics have been spoken for.

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Yeah, sorry, I still need to respond to everyone who has emailed me, but to be brief: you're pretty much spot on with what I'm looking for in that chapter. I'll send a more detailed response later, but I'm late picking up my daughter [grin]

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Idea: Create a closed WiKi, that you open up to possible Authors, and everyone can chip in a bit, although there will allways be "Chapter Supervisors" of course, to make sure everything falls into place.

I for one, although I don't see myself writing any of these chapters, I can do some assistant work, in researching examples, tutorials, code, etc...

I do feel that there aren't any game programming books out there that really sit down with the reader and guide them through two key areas: Multithreading and plugin designs.

These are areas that are either filled up with myths, or beginners coders just see them as too complex, when they're really not...

In regards to graphics code per se, there should be a book out there with a decent BSP primer, instead of historical snippets like "BSPs where used in Doom...", and a decent intro, backup up by a downloadable demo or library, shouldnt take more than 20 pages, if I'm not grossely underestimating it.

What do you guys think of my thoughts?

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Prozak: I agree as well, but _the_phantom_ is right, both are outside the scope of this book.

Anyway, I just updated the ToC. Most topics have at least one tentative author at this point, but there are still a few topics that need to be covered:

1.6 - Disabling VSync (I'll probably just write about this)
1.7 – Framebuffer Objects (will probably be included in the render-to-texture section anyway - either way I can write about it as well)
3.0 - ARB_vertex_program and ARB_fragment_program
5.7 - Dynamic Light Mapping
5.8 - Detail Maps
6.8 - HDR lighting
6.9 – Explosions
7.1 – Skies
7.1.1 – Skyboxes
7.1.2 – Skyplanes
7.1.3 – Skydomes
7.1.4 – Dynamic methods
7.3 - Clouds

Originally, the skies topic was marked as taken because I have an article that I wrote for another book a couple of years ago that I was going to update, but the article was pretty basic (focusing on static skyboxes), and I think there are people here who are capable of writing about much more exciting techniques (perhaps I could include my stuff as an intro to the basics and someone else could add more on dynamic methods)

In regards to the additional chapter ideas, at this point, it looks like we'll definitely be including a chapter scene management/visibility determination, etc. Someone has offered to write an OpenAL chapter, but I'm beginning to feel that it's a little off topic for the book.

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Quote:
Original post by Myopic Rhino
Someone has offered to write an OpenAL chapter, but I'm beginning to feel that it's a little off topic for the book.


Darn! [wink] I think your right Dave, this book would be better just for the OpenGL specifics in relation to Game Programming. I mean it's not about making games with OpenGL, otherwise there would need to be info on the other components such as input, file i/o, etc...

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Quote:
Original post by Myopic Rhino
Prozak: I agree as well, but _the_phantom_ is right, both are outside the scope of this book.

In regards to the additional chapter ideas, at this point, it looks like we'll definitely be including a chapter scene management/visibility determination, etc.



Someone just has to sit down and tackle that issue, the lack of decent tutorials on the subject is appaling.

Thank you for taking my thougts on the subject into consideration.

*...goes back to finishing his own Lua tutorial...*

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Sounds like a good idea! It provides non-professionals with the chance to show their potential and knowledge through a book that addresses many in the industry.

A few questions:

Does this work as a competition - everybody submits and article and you choose the best or combine them or do you pick an author which will do the work?

Can the articles include pictures? How many? Generally I see books refrain from using too many pictures.

How long should one section of a chapter be?

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Quote:
Original post by Ilici
Does this work as a competition - everybody submits and article and you choose the best or combine them or do you pick an author which will do the work?
No, not exactly. I'm going to choose the author in advance based on a brief proposal and summary of what they want to cover. I'll also take their bio (or if they are active here, what I know about them from the forums) into account when determining whether or not I think they can deliver what they say they will. There are some people here (including you) that I would automatically approve, no matter what they wanted to write about.
Quote:
Original post by Ilici
Can the articles include pictures? How many? Generally I see books refrain from using too many pictures.
Yeah, they really *should* include pictures. I'd like to see at least one figure every 2-3 pages, though more isn't bad if it's appropriate for the topic.
Quote:
Original post by Ilici
How long should one section of a chapter be?
Depends on the topic. 2-8 pages should be enough for most of the topics listed here, though a few will be longer (and a couple can be a page or so). That's assuming minimal code listings.

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HI! i think this book is necesary for the OpenGL game dev comunity , i think that is very useful a topic in Editors and tools programing (GTK and MFC) some basic but useful tutorial what do you think?
see u

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      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 two samples, asteroids performance benchmark and example Unity project that uses Diligent Engine in native plugin.
      AntTweakBar sample is Diligent Engine’s “Hello World” example.

       
      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 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 and Android platforms. Direct3D11, Direct3D12, OpenGL/GLES backends are now feature complete. Vulkan backend is coming next, and support for more platforms is planned.
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