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OpenGL Shading Language
Because of its orange cover, the book is also called the "Orange Book," and together with its siblings, the classic "Red Book" (aka OpenGL Programming Guide) and the "Blue Book" (aka OpenGL Reference Manual (see this earlier review), it is a member of the OpenGL family of books from Addison-Wesley. Although it has a short overview of the basic features of OpenGL, it is intended for an audience that is already somewhat familiar with OpenGL and with 3D graphics programming in general. The interested reader should probably have read the "Red Book" or at least have a good understanding of how to use the OpenGL graphics API before attempting to tackle this book.
Rost, as well as the co-authors on some of the chapters, John M. Kessenich and Barthold Lichtenbelt, all employees of the graphics hardware vendor 3Dlabs, were driving forces behind the inception of the OpenGL Shading Language. They are also core contributors to the final language specification as well as the OpenGL extensions that provide the framework for this new shading language. So the information in the book actually comes from the people that created the language, which is a definite plus.
The book consists of 17 chapters and two appendices which can be roughly categorized into four major parts: An introduction to the basics of OpenGL and GPU programmability; a description of the OpenGL Shading Language and the associated OpenGL extensions; a number of chapters that show the shading language in action; and finally a reference section on the language grammar and the entry points introduced by the new OpenGL extensions. Each chapter of the book has numerous interesting references to get further information on the presented topics. I can only recommend taking a closer look at some of them.
The first two chapters of the book describe the basics of the OpenGL graphics API, followed by an overview of the new programmable processors in the graphics pipeline and an overview of the shading language used to program them. The introductory chapter on OpenGL basics is very well written and worth the read even for more experienced OpenGL programmers. However, as mentioned above, the reader should have enough expertise in using OpenGL to be able to understand the more advanced parts of the book. The introductory chapter won't be enough in my opinion.
The third chapter, written by John Kessenich - one of the main authors of the OpenGL shading language specification - presents the language definition. This chapter is where the basic data types as well as the available control structures are described in detail. For people interested in writing a compiler for the OpenGL Shading Language, Appendix A also contains the entire language grammar in BNF.
Chapter four moves on to describe the programmable graphics pipeline, which was first introduced in the second chapter, in more detail. The programmable vertex and fragment processors and their interaction with OpenGL's fixed functionality are presented. In chapter five, the description of the shading language concludes with the available built-in functions. Chapter six offers the first simple example that shows the shading language in action - a shader to procedurally create a brick texture.
Until this point, the book doesn't talk much about how to integrate shaders into the host program running on the CPU. New OpenGL extensions were created for this purpose, in particular GL_ARB_shader_objects, GL_ARB_vertex_shader, and GL_ARB_fragment_shader. Chapter seven contains detailed descriptions of the entry points provided by these new extensions. Among other things, it describes how shader objects are created, compiled, and then linked to form shader programs that can then be used to render objects. Appendix B also has a reference section on the new entry points similar in style to the "Blue Book." Chapter seven concludes the dry, technical part of the book that introduced both the shading language and the necessary infrastructure to use it from a host program running on the CPU.
The remaining chapters delve into the really interesting topic: shader development. These chapters offer multiple ideas on what can be done with shaders and how to effectively use them in graphics programming. Standard techniques, such as bump mapping, procedurally creating textures, using noise, and others, are presented. Chapter nine deserves special mention because it presents shaders that mimic the behavior of the OpenGL fixed-function pipeline. Many developers new to shader programming are faced with re-implementing certain features offered by OpenGL's fixed functionality. This chapter addresses this.
Chapter fourteen also deserves mention. Shaders that procedurally create textures usually suffer from aliasing artifacts. This chapter shows a number of anti-aliasing techniques to diminish these artifacts. In my opinion, this important topic has not received the attention it deserves -- it's good to see such a chapter in this book.
Closing this section of the book, chapters fifteen and sixteen describe some interesting non-photorealistic shaders and shaders for doing image processing. (For more ideas on what can be done with shaders I also recommend the book "GPU Gems", which I have read and reviewed some time ago.
The final chapter of the book (chapter seventeen) is a language comparison with other high-level shading languages such as the RenderMan Shading Language, SGI's Interactive Shading Language from the OpenGL Shader package, Microsoft's HLSL, and NVIDIA's Cg. Although I am quite familiar with most of these languages, I found this chapter to be an interesting read because it attempts to look at the languages objectively, listing advantages and disadvantages of the various approaches.
The book contains many diagrams and images, all in black and white, except for 16 pages containing 30 color plates in the middle of the book. Most of the images are not overly "flashy" but do give a practical idea of the types of rendered images a particular shader can produce.
There is also a website for the book where you can find an errata list and download a sample chapter (chapter six). As mentioned above, this chapter develops a simple brick shader to show the basic features of the shading language. The website also has all the shaders presented in the book available for download. Because the book does not come with a CD-ROM this is the only means of getting shaders code without having to type them. At the time of this review, the site appeared to be in a transitional state.
Rost's OpenGL Shading Language succeeds at giving a good introduction to shader programming with the OpenGL Shading Language. Not only does it provide the necessary technical instruction to allow the reader to write his/her own shaders as well as integrate them with the host program, it also demonstrates a number of practical applications for shaders and tries to encourage exploring the new dimension of real-time graphics programming opened up by the OpenGL Shading Language. Since there is no other book currently available on this topic, it is hard to say whether the "Orange Book" will stand the test of time and actually become the reference book on the OpenGL Shading Language, but I believe it will.
Ecker has been involved in real-time graphics programming for more than 9 years and works as a arcade game developer. He also works on a graphics-related open source project called XEngine. You can purchase OpenGL Shading Language from bn.com. Slashdot welcomes readers' book reviews -- to see your own review here, carefully read the book review guidelines, then visit the submission page.
Although it has a short overview of the basic features of OpenGL, it is intended for an audience that is already somewhat familiar with OpenGL and with 3D graphics programming in general
Boy, I hope someone looking to learn OpenGL at least knows enough about 3D graphics to realize this isn't likely the right book to start learning OpenGL with. That said, the Red and Blue books are indispensable. I certainly hope this "Orange" book lives up to the family reputation.
Anyone know if Doom 3 uses these newly ratified extension? I would imagine it does - but I of course have no facts to back this up.
It will take a while for drivers supporting OpenGL's SL to be widely distributed, and existing artist-centric shader design tools to be updated for the new standard, but things seem to be moving very quickly.
There are still a few areas where I wish the OpenGL ARB would follow DirectX's lead -- a library like D3DX and a generic mesh format similar to DirectX X files would be really nice (there are various Open Source projects that fit this bill, but AFAIK, none of them are official or have any sort of critical mass).
Of course, a developer can easily create his/her own code that does similar things to D3DX using OpenGL, but having such a functional officially-supported utility library really helps when you're prototyping and just want to get things up and running quickly and also helps if you're just beginning with 3D programming, so you aren't completely overwhemled by everything.
For one thing, GLSL is an incredibly easy language to compile compared to C++ or C#. That aside, 3Dlabs has written the source code to the GLSL compiler and released that source code for anyone to use, including competitors like ATI or NVIDIA.
But my main disagreement is with the idea of having an ARB-specified intermediate language. I already described my position in another post, so I won't repeat it all here.. but I think your position is short-sighted. I think allowing the IHVs to do the full compile/optimization stuff will provide them with greater flexibility and greater potential for innovation.
GLSL is still a fairly simple language, compared to something like c/c++, so writing a compiler should not be extremely difficult.
The big advantage of passing the high level code straight to the driver is that it allows for easier optimizations, simply because the conversion from high level -> assembly/bytecode inevitebly loses some of the context.
For instance (I don't know HLSL, but I have used Cg, which I'm told is almost identical to HLSL), the smoothstep() function provides a nice, smooth interpolation between two values. When I compile my Cg shader down to arb_vp (the assembly language), smoothstep has to be expanded to perform all the necessary arithemtic instructions sequentially, because there is no comparible instruction.
If the high level code were passed directly on to the driver, the driver could determine if for instance, this was a new piece of hardware that didn't exist when the game was made, and this hardware has dedicated smoothstep functionality, allowing the operation to be performed much faster than sequential instructions. The same information could be recovered from the bytecode, but it would be much more difficult.
The same general principle holds in other languages. Higher level doesn't necessarily mean slower or more difficult compilers. Look at Apple's extensions to C to allow easy utilization of the PowerPC's vector processor. A little hint from the programmer can make the job of writing an optimizing compiler much easier.
...because I think OpenGL would have been relegated to academia and top-end engineering applications at most if he hadn't used OpenGL for his Quake engines.
Why do I care about this? Because M$ only produces/copies acceptable technologies when heavy pressure is applied to them or if they are playing catch-up. Look at IE for example. I speculate that DirectX would have dominated as the graphics API but would have followed a similar fate to IE if it hadn't been for OpenGL racing along with decent drivers all because of this thing called Quake.
Thinking short-term as a developer, I would have loved if the world had one standard, even for shaders, but I take off my hat to Darwin and accept a little hardship implementing for two or more APIs to let them evolve each other.