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Metaprogramming GPUs with Sh
Martin Ecker writes "With the advent of powerful, programmable GPUs in consumer graphics hardware, an increasing number of shading languages to program these GPUs has become available. One quite interesting language that - in many ways - has a very different approach than other mainstream shading languages (such as Cg or the OpenGL Shading Language) is Sh. The recently released book "Metaprogramming GPUs with Sh" by Michael McCool and Stefanus Du Toit, both major contributors to the Sh project, explains the basics of the Sh high-level shading language and the corresponding API and also goes into some of the details of the implementation. The book is intended for an audience that is already familiar with traditional shader development for programmable GPUs. Also, a firm background in 3D graphics programming and C++ is a must for the interested reader." Read on for the rest.
Metaprogramming GPUs with Sh
author
Michael McCool, Stefanus Du Toit
pages
308
publisher
A K Peters
rating
7/10
reviewer
Martin Ecker
ISBN
0321197895
summary
A book that describes an interesting shading language and accompanying API to program GPUs.
Before discussing the book in more detail, I will try to give a basic overview of Sh, since most readers will not be familiar with it. For a more in-depth look at Sh, I recommend taking a look at a recently posted Gamasutra article by Michael McCool (http://www.gamasutra.com/features/20040716/mccool _01.shtml), the paper on Sh from the authors presented at the recently held SIGGRAPH 2004 conference (http://www.cgl.uwaterloo.ca/Projects/rendering/Pa pers/#algebra), and of course the Sh homepage at http://www.libsh.org.
Sh started out as a research project at the University of Waterloo (http://www.cgl.uwaterloo.ca), and it is both a shading language and a runtime API to use the Sh shaders. As a shading language Sh is embedded into C++ as a domain-specific language, which is made possible by using C++ operator overloading and by defining special tuple and matrix types that are used extensively in shader code. So instead of defining its own language that requires a full compiler, like other shading languages do, Sh uses regular C++ syntax to describe shader code, which is then dynamically (at runtime) compiled to a specific backend, such as a GPU or possibly even the CPU. In addition to compiling to a specific GPU or CPU target, Sh can also be used in a special stream mode where a shader is applied to a stream of input tuples. This is very useful for general purpose GPU programming where the GPU is basically used as an additional processor to the host CPU (see http://www.gpgpu.org for more information on the subject). Finally, Sh code can also be executed in an immediate mode where every Sh statement is directly executed on the host CPU (without being compiled into a shader program), which makes it very easy to debug shaders with any host debugger running on the CPU.
Due to the way Sh is embedded into C++, the full range of abstraction mechanisms offered by C++ can be used to structure and modularize shader code. Abstract base classes, regular functions, templates, and any other features offered by C++ can be used to develop shaders. This is an interesting consequence of the metaprogramming approach of Sh that also allows the use of software engineering principles in shader development, such as object orientation, that other shading languages currently cannot offer.
This kind of metaprogramming in C++ is used by an increasing number of libraries. For example, the Spirit parser framework (see http://spirit.sourceforge.net) uses a similar approach to describe and generate parsers directly in C++ instead of using traditional external tools, such as yacc or bison.
One of the most fascinating features of the Sh toolkit is the possibility to combine and connect shader programs to form new shader programs, which allows one to easily build complex shaders out of simple shader fragments. In a more general sense, Sh provides what can be called a shader algebra (see also the aforementioned SIGGRAPH 2004 paper), where shader programs are the objects on which special operators to combine and connect them are defined. An interesting application of this shader algebra is to specifically bind certain varying shader inputs to uniform variables and the other way around (this is what functional programming languages usually call currying). Also combining a matrix palette skinning shader with any light model shader (or any shaders that perform specific tasks, for that matter) is easily possible.
After this short introduction to the Sh toolkit, we shall now take a closer look at the book "Metaprogramming GPUs with Sh".
The book is split into three parts, an introduction, a reference, and an engineering overview.
The introduction consists of the first five chapters and discusses the basics of the Sh shading language and the API. In particular, the tuple and matrix types and the operators defined on them are presented. The way shader programs are defined and how parameters and attributes are handled is discussed, followed by the way textures are represented. Finally, the stream and channel concept used to feed data into shader programs is discussed. These introductory chapters contain a number of examples that demonstrate the presented concepts. Chapter three contains a quite interesting sample shader that uses constructive solid geometry techniques and metaprogramming in Sh to render text. While not the most useful use case, the shader shows some interesting capabilities of Sh, in particular the shader algebra operators. Chapter four on textures has some more nice sample shaders for doing shiny bump mapping, rendering wood and marble, and using Worley noise.
The second part of the book is a reference on Sh. Unlike references in many other computer books, this is not just a technical listing of the available features of Sh but is written in regular prose (with the occasional reference-like table here and there). The six chapters of the reference section describe how to setup and use the Sh library, and then discuss the available types, operators, and standard library functions more thoroughly than in the introduction. Additionally, the available backends are mentioned in the last chapter of this part of the book. A draft of the reference manual can also be found online at http://www.libsh.org/ref/online.
The final part of the book deals with engineering aspects of Sh. These final five chapters of the book discuss the details of the current implementation. The intermediate representation for shaders that is used by Sh is presented as well as how streams and textures are managed and stored internally. The interface between the Sh frontend and the various specific backends is discussed, as well as the current state of the optimizer including some further improvements that are planned in the future.
The images in the book are all in black and white except for 14 color plates in the middle of the book. The color plates and other images usually show teapots or animals, so they aren't all that exciting, but do demonstrate what the sample shaders presented in the book look like.
The book does not come with a CD-ROM, but with such a young library that is still under heavy development, putting a snapshot of the library's source code base on a CD-ROM would be a waste of resources. Sh itself as well as all sample shaders presented in the book can be downloaded from the Sh homepage at http://www.libsh.org. This website also has additional documentation, including some papers and the API reference documentation generated with Doxygen from the sources. Sh is distributed under a very liberal open source license (based on the zlib/libpng license) that also allows commercial use.
For the reader with enough expertise in 3D and shader programming, this book provides a concise and well-written introduction to Sh. The book will definitely contribute to enlarging the currently relative small user base of Sh and hopefully help the library grow and get more refined in the near future. Everyone familiar with "regular" high-level shading languages, such as Cg or the OpenGL Shading Language, should take a look at this book to see a new and interesting way of programming GPUs that the aforementioned languages do not offer.
About the review author:
The author has been involved in real-time graphics programming for more than 9 years and works as a games developer for arcade games. In his rare spare time he works on a graphics-related open source project called XEngine http://xengine.sourceforge.net.
Before discussing the book in more detail, I will try to give a basic overview of Sh, since most readers will not be familiar with it. For a more in-depth look at Sh, I recommend taking a look at a recently posted Gamasutra article by Michael McCool (http://www.gamasutra.com/features/20040716/mccool _01.shtml), the paper on Sh from the authors presented at the recently held SIGGRAPH 2004 conference (http://www.cgl.uwaterloo.ca/Projects/rendering/Pa pers/#algebra), and of course the Sh homepage at http://www.libsh.org.
Sh started out as a research project at the University of Waterloo (http://www.cgl.uwaterloo.ca), and it is both a shading language and a runtime API to use the Sh shaders. As a shading language Sh is embedded into C++ as a domain-specific language, which is made possible by using C++ operator overloading and by defining special tuple and matrix types that are used extensively in shader code. So instead of defining its own language that requires a full compiler, like other shading languages do, Sh uses regular C++ syntax to describe shader code, which is then dynamically (at runtime) compiled to a specific backend, such as a GPU or possibly even the CPU. In addition to compiling to a specific GPU or CPU target, Sh can also be used in a special stream mode where a shader is applied to a stream of input tuples. This is very useful for general purpose GPU programming where the GPU is basically used as an additional processor to the host CPU (see http://www.gpgpu.org for more information on the subject). Finally, Sh code can also be executed in an immediate mode where every Sh statement is directly executed on the host CPU (without being compiled into a shader program), which makes it very easy to debug shaders with any host debugger running on the CPU.
Due to the way Sh is embedded into C++, the full range of abstraction mechanisms offered by C++ can be used to structure and modularize shader code. Abstract base classes, regular functions, templates, and any other features offered by C++ can be used to develop shaders. This is an interesting consequence of the metaprogramming approach of Sh that also allows the use of software engineering principles in shader development, such as object orientation, that other shading languages currently cannot offer.
This kind of metaprogramming in C++ is used by an increasing number of libraries. For example, the Spirit parser framework (see http://spirit.sourceforge.net) uses a similar approach to describe and generate parsers directly in C++ instead of using traditional external tools, such as yacc or bison.
One of the most fascinating features of the Sh toolkit is the possibility to combine and connect shader programs to form new shader programs, which allows one to easily build complex shaders out of simple shader fragments. In a more general sense, Sh provides what can be called a shader algebra (see also the aforementioned SIGGRAPH 2004 paper), where shader programs are the objects on which special operators to combine and connect them are defined. An interesting application of this shader algebra is to specifically bind certain varying shader inputs to uniform variables and the other way around (this is what functional programming languages usually call currying). Also combining a matrix palette skinning shader with any light model shader (or any shaders that perform specific tasks, for that matter) is easily possible.
After this short introduction to the Sh toolkit, we shall now take a closer look at the book "Metaprogramming GPUs with Sh".
The book is split into three parts, an introduction, a reference, and an engineering overview.
The introduction consists of the first five chapters and discusses the basics of the Sh shading language and the API. In particular, the tuple and matrix types and the operators defined on them are presented. The way shader programs are defined and how parameters and attributes are handled is discussed, followed by the way textures are represented. Finally, the stream and channel concept used to feed data into shader programs is discussed. These introductory chapters contain a number of examples that demonstrate the presented concepts. Chapter three contains a quite interesting sample shader that uses constructive solid geometry techniques and metaprogramming in Sh to render text. While not the most useful use case, the shader shows some interesting capabilities of Sh, in particular the shader algebra operators. Chapter four on textures has some more nice sample shaders for doing shiny bump mapping, rendering wood and marble, and using Worley noise.
The second part of the book is a reference on Sh. Unlike references in many other computer books, this is not just a technical listing of the available features of Sh but is written in regular prose (with the occasional reference-like table here and there). The six chapters of the reference section describe how to setup and use the Sh library, and then discuss the available types, operators, and standard library functions more thoroughly than in the introduction. Additionally, the available backends are mentioned in the last chapter of this part of the book. A draft of the reference manual can also be found online at http://www.libsh.org/ref/online.
The final part of the book deals with engineering aspects of Sh. These final five chapters of the book discuss the details of the current implementation. The intermediate representation for shaders that is used by Sh is presented as well as how streams and textures are managed and stored internally. The interface between the Sh frontend and the various specific backends is discussed, as well as the current state of the optimizer including some further improvements that are planned in the future.
The images in the book are all in black and white except for 14 color plates in the middle of the book. The color plates and other images usually show teapots or animals, so they aren't all that exciting, but do demonstrate what the sample shaders presented in the book look like.
The book does not come with a CD-ROM, but with such a young library that is still under heavy development, putting a snapshot of the library's source code base on a CD-ROM would be a waste of resources. Sh itself as well as all sample shaders presented in the book can be downloaded from the Sh homepage at http://www.libsh.org. This website also has additional documentation, including some papers and the API reference documentation generated with Doxygen from the sources. Sh is distributed under a very liberal open source license (based on the zlib/libpng license) that also allows commercial use.
For the reader with enough expertise in 3D and shader programming, this book provides a concise and well-written introduction to Sh. The book will definitely contribute to enlarging the currently relative small user base of Sh and hopefully help the library grow and get more refined in the near future. Everyone familiar with "regular" high-level shading languages, such as Cg or the OpenGL Shading Language, should take a look at this book to see a new and interesting way of programming GPUs that the aforementioned languages do not offer.
About the review author:
The author has been involved in real-time graphics programming for more than 9 years and works as a games developer for arcade games. In his rare spare time he works on a graphics-related open source project called XEngine http://xengine.sourceforge.net.
You can purchase Metaprogramming GPUs with Sh from bn.com. Slashdot welcomes readers' book reviews -- to see your own review here, read the book review guidelines, then visit the submission page.
It may well be my utter ignorance of how GPUs work, but it would be nice, if possible, to have tools to utilize all of that computing power when I'm just displaying a simple GUI or text interface. I understand GPUs are heavily optimized for what they do, but I expect they're still good for general purpose tasks and might be really useful in some math-heavy applications.
Proud member of the Weirdo-American community.
isn't sh the basic (old-school) Bourne Shell and bash a version with enhanced scripting abilities?
:-)
Yes I know-- sh in this case is shading language...
But on a more serious note, is there any reason why once cannot write to the video card (as root) with a bash script? Is there any technological reason why one cannot send in the OpenGL information this way?
If not, maybe we need command-line programs to connect to irrlicht then we can do all this
LedgerSMB: Open source Accounting/ERP
Well that's good to know Stefanus. If your performance claims are true, I guess I'll have to take a look at Sh then :-) Now that MK6 is just about wrapped up, the guys on my team are eager to get a chance to learn and explore new technology for upcoming games.
And here's a question that's sure to anger the general Slashdot crowd -- however, the answer will be important in whether or not your language makes it into common usage in the game industry. How do you feel about the use of your technology in closed source proprietary products (like video games)?
The GPU ought to be able to be optimized for FP arithmetic, also.
This idea is not mine, but back when the first Netra came out, a couple of guys here in Houston who used to optimize Crays figured out how to use the GPU to do floating point arithmetic a whole magnitude faster than Sun knew it could be done.
My optimization skills are a little rusty, but the same architectural elements are there in the ATI graphics cards.
If some one does this, drop me a line and tell me how you did it.
"The mind works quicker than you think!"
It is one place that an OS architecture which makes a clean separation of GUI and kernel would win over the mess of sundry .dlls from the Criminal Monopoly. The other place would have been the ill-fated tablet computer, had it been correctly designed, with the X serevr on the portable bit.
Because simple single-processor relatively high-performance silicon is now very affordable, the time is right to go back to parallelism, dedicated I/O and graphics processors, etc, to get even better performance.
It would be nice to have a GPU compiler to run ordinary code, such as X, but the compiler would be different for each architecture, not like AMD vs Intel, where you can use the same compiler with just the optimisations tweaked. But my thinking is to replicate a full CPU in the GPU chip or at least on the graphics card. You could put a Pentium/Athlon there, feeding the gPU as usual, fed itself from the AGP bus or its successor via a big FIFO.
But whatever way things go, I do think we are in for some big steps forward in graphics processing, at least. I am not into shaders and so on, I don't need fast 3-D or anything like that, but I know that many people do, and not just for games. But if it offloads things from my main CPU, I would find immediate benefit.
On SGI machines there is a '/dev/opengl', that one can pipe openGL bytecode to.
"A language that doesn't affect the way you think about programming, is not worth knowing" - Alan Perlis