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In the Name of God. Shader Programming Fundamentals By: Ali Seyedof Tochal Advanced Systems, Ltd.

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Presentation on theme: "In the Name of God. Shader Programming Fundamentals By: Ali Seyedof Tochal Advanced Systems, Ltd."— Presentation transcript:

1 In the Name of God

2 Shader Programming Fundamentals By: Ali Seyedof Tochal Advanced Systems, Ltd.

3 Preface Workshop Content History of shaders Why using them Types of shaders Tools of the trade HLSL language basics Implementing a simple effect Some more effects … Prerequisites C/C++ Programming Computer Graphics DirectX API/Programming But don’t worry, all of you will learn something useful! 3

4 Computer Graphics Transformations Lighting Texturing Shadows Effects … If you have done all above, you have done computer graphics Problems Complex (Time/Space consuming) task Lots of floating point calculations Limited hardware and software power/support Is not the exact physical model of the real world (Important) More problems when doing real-time graphics e.g. Computer Games 4

5 Computer Graphics Cont’d Who handles the task? Human (Not our topic, like painters e.g. da Vinci) Software (Software rendering, like old games e.g. Quake) Hardware (Hardware Accelerated rendering, like modern games) Rules Hardware implementation is faster than software (in most cases) Hardware is not flexible (As its name says ) Software is slow but very flexible and extensible How about a hybrid solution?? 5

6 History (Home Computes) Home Computers Era ( ) Commodore Amiga Atari Sinclair ZX Spectrum Amstrad CPC … Features Used for games and entertainment Limited 2D graphics Performed better than PC’s Had limited hardware gfx acceleration and dedicated graphics processors (Bit-Blitting, Panning, Palette tricks…) Maximum of 4096 colors 6

7 History (Early PC’s) Early Personal Computers ( ) Started from MDA graphics cards for IBM From text only display to SVGA resolution Many vendors for CPU, Graphics adapters 7

8 History (Early PC’s) Cont’d Features With purpose of business tasks Limited usage for games and entertainment Limited 2D graphics Poor graphics performance compared to home computers and gaming consoles Had limited hardware gfx acceleration (Bit-Blitting, Panning, Palette tricks…) But growing much faster in both technology and user base More computing power led to creation of first vector based and even 3D games 8

9 History (3D Accelerators) Hardware Accelerated PC Gfx ( ) Reaching the limitations of CPU base Gfx (Software) SGI already had kind of hardware accelerators Voodoo and S3 Virge came to life Graphics Programming API’s Close competition on producing more powerful accelerators in 90s 9

10 History (3D Accelerators) Cont’d Features Limited support for Graphics Pipeline Still needed CPU for some stages Focused on Rasterization/Texturing/Z-Buffering No hardware T&L Fixed Pipeline Diversity of programming API’s Relatively expensive Not very popular among both users and developers 10

11 Graphics Pipeline The process of graphics is a pipeline To be implemented in machine (hardware/software) Has different stages 1- Transform : Transforming from world to image space 2- Lighting: Doing light properties on a per-vertex basis 2-Triangle setup/clipping in image space 3-Rasterizing: Converting from vectors to pixels and drawing the pixels on the output buffer (screen) 11

12 Graphics Pipeline Cont’d Where to implement each stage? Early 3D accelerators focused on the final stages Different types of calculation in each stage Different type of data in each stage Different amount of data in each stage CPU can do everything in a serial manner CPU is good at integer calculations not floats Early 3D accelerators are partial hardware implementation of the gfx pipeline This is why we call them Accelerators not GPUs 12

13 Graphics API’s What is required to use hardware in apps? Each hardware needs a driver Each hardware/driver needs an API to be used by developer Many hardware vendor means many API’s (bad) The need for some generic/standard/widely accepted & used API 13

14 Graphics APIs Cont’d Glide by 3DFx Popular in early era Preferred over OpenGL! Failed because the brand failed in hardware competition and driver support by OS’s and API support by other brands OpenGL by Silicon Graphics Early versions had compatibility issues Not so friendly Needed serious overhaul Very portable 14

15 Graphics APIs Cont’d DirectX by Microsoft Not popular at early era Limited to windows platform Got popular in the next decades Nice hardware abstraction layer to support all hardware vendors More and faster revisions than OpenGL Currently dominates the PC game development 15

16 Back to History (GPUs) GPU (Graphics Processing Unit) GeForce 256 by NVidia in 1999 The first card which implemented all stages in hardware The term Hardware T&L The whole graphics pipeline done in hw So this is called the first GPU which did Processing not just some interpolation 16

17 History (Gfx Pipeline) 17

18 Back to History (GPUs) Programmable Pipeline GeForce 3 card by NVidia in 2001 A revolution in the history of real-time graphics and games Made advanced effects possible in real-time Opened doors of creativity to graphics programmers What is the so called fixed/programmable pipeline 18

19 Fixed Pipeline Fixed Pipeline or Fixed Function Pipeline 19

20 Programmable Pipeline 20

21 Fixed vs. Programmable Pipeline Fixed Pipeline Limitations/Problems Fixed pipeline stages are all implemented in hw No change or limited change to them You can just change some states and values to control drawing Impossible to implement many complex or even simple lighting models/formulas/effect Needed hardware implementation/support to do those effects Real-time graphics and games now more interested in visual quality than quantity (game world size) 21

22 Fixed vs. Programmable Cont’d What Programmable Pipeline Offers Programmability of the stages (flexibility) More complex formulas/lighting models More general code in application side More space for creativity and hardware improvement But more complex to learn/implement Lack of good authoring tools Lack of good debuggers/profilers Lack of good support in content authoring tools e.g. 3dsmax/maya Lack of good support in file formats and exchange of data 22

23 Shaders What are shaders? The program that controls or runs in an stage is called shader The concept shader was first introduced in RenderMan software by Pixar but not in real-time We have different kind of shaders depending on their occurrence in the graphics pipeline They are pieces of code written by programmer or even artist The shader code runs on the GPU side not CPU Different languages for shader programming 23

24 Shaders Shader Types Vertex Shader – Since the first programmable cards – Takes vertex data from application – Does per-vertex calculations e.g. T&L – Runs on every vertex input Pixel Shader – Since the first programmable cards – Takes pixel data from rasterizer stage – Does per-pixel calculations e.g. Bump Mapping – Runs on every input pixel Geometry Shader – Since Shader Model 4.0 and Geforce – Needs DX10+ or OpenGL 3.2+ (OpenGL 2.0 via extentions) – Takes the output of vertex shader to generate 0 or more primitives (generates new primitive) – Useful in particles, cubemap rendering, terrains, tesselation,… Hull Shader, Compute Shader, Domain Shader – New Shader Model 5.0 shaders used for tesselation, higher order surfaces,… 24

25 Shader Programming Languages HLSL (High Level Shading Language) Developed by Microsoft for DirectX Available since DX9.0 Microsoft provided the Effect Framework on this C like syntax Used in Windows and Xbox Poor authoring support by MS (VS2012 going to change this) Good support in content authoring apps (3dsmax,…) Updates with the latest shader model Limited to both hardware and software (OS and API) platform Used in many games 25

26 Shader Prog. Langs. GLSL GLSL (OpenGL Shading Language) Developed by Khronos group Available since OpenGL 2.0 C like syntax Available on OpenGL supported devices Poor authoring tools Poor support in content authoring tools Poor support in debugger/profiler tools Updates less frequently and later than others Good platform portability but limited API (OpenGL) Only option in handheld platforms like iDevices and Android Used in some GL games 26

27 Shader Prog. Langs. Cg Cg (C for Graphics) Developed by NVidia Available since OpenGL 2.0 C like syntax, much like HLSL Is not dependent on platform or API ! Good authoring tools Medium support in content authoring tools Good support in debugger/profiler tools NVidia developed useful tools for Cg Independent from hw, OS, API, its in a higher abstraction layer Used in many games Harder to develop than HLSL in Windows (Needs extra tools, run- time DLLs,…) No wrappers, tools for newer devices like handhelds 27

28 Shader Prog. Langs. Summary Shader Programming Languages Summerized 28

29 Shader Models Shader Model Some kind of standard or feature set/feature level Describes the instruction set Describe the capabilities Describe hardware specs like # of registers, instruction slots, etc Unified Shader Model: is something else which discusses about having the same shader caps and instruction set in vertex/pixel/geometry and other TYPES of shaders. 29

30 Shader Models (DirectX) Shader Models in DirectX Please note DirectX versions prior to DirectX 8.0 do not support shader models DirectX Shader Model 1.0 & 1.1 DirectX 8.0a - Shader Model 1.3 DirectX Shader Model 1.4 DirectX Shader Model 2.0 DirectX 9.0a - Shader Model 2.0a DirectX 9.0b - Shader Model 2.0b DirectX 9.0c - Shader Model 3.0 DirectX 10.0* - Shader Model 4.0 DirectX 10.1* - Shader Model 4.1 DirectX 11.0* - Shader Model 5.0 DirectX 11.1* - Shader Model 5.0 *DirectX 10.0 and higher will not run in Windows XP 30

31 Shader Models (OpenGL) Shader Models in OpenGL OpenGL Texture objects OpenGL D textures, BGRA and packed pixel formatspacked pixel OpenGL Multitexturing, multisampling, texture compressionMultitexturingmultisampling OpenGL Depth textures OpenGL VBO, Occlusion Queries [2]VBO [2] OpenGL GLSL 1.1, MRT, Non Power of Two textures, Point Sprites, Two-sided stencilGLSLMRTPoint Sprites OpenGL GLSL 1.2, Pixel Buffer Object (PBO), sRGB TexturesGLSL OpenGL GLSL 1.3, Texture Arrays, Conditional rendering, FBOGLSL OpenGL GLSL 1.4, Instancing, Texture Buffer Object, Uniform Buffer Object, Primitive restartGLSL OpenGL GLSL 1.5, Geometry Shader, Multi-sampled texturesGLSL OpenGL GLSL 3.30 Backports as much functionality possible from the OpenGL 4.0 specificationGLSL OpenGL GLSL 4.00 Tessellation on GPU, shaders with 64-bit precisionGLSL OpenGL GLSL 4.10 Developer-friendly debug outputs, compatibility with OpenGL ES 2.0GLSL OpenGL GLSL 4.20 Shaders with atomic counters, transform feedback, shader packing, performance improvementsGLSL OpenGL 4.3 – For all versions of OpenGL 3.3 and above, the corresponding GLSL version matches the OpenGL version. So GL 4.1 uses GLSL Direct3D Shader Model 4.0 is equivalent to GLSL version Earlier GLSL versions for OpenGL 3.x provide subsets of this functionality, based on the available functionality in the OpenGL version, though 1.50 is almost feature-identical to SM4. Direct3D Shader Model 5.0 is equivalent to GLSL version For earlier shader models, GLSL versions less than 1.30 are used 31

32 Vertex Shaders in Shader Models 32

33 Pixel Shaders in Shader Models 33

34 Beginning HLSL Programming Why HLSL The tool setup is easier Only requires Visual Studio and DirectX SDK So easier to write a hello world Majority of us (in Iran) are Windows programmers and almost all games are developed for Windows/DX Used widely in PC games worldwide The basics are the same between all shader languages 34

35 Doing an HLSL Hello World Workflow Install Microsoft Visual Studio Install Microsoft DirectX SDK (latest version is June 2010) Create a new project (C++/C#) (Dialog Based or Win32, doesn’t really matter) Setup the required directories for the project (DX include/lib paths) Create a device and setup a simple scene (Requires DX programming knowledge) Write the shader Create an Effect object in the application, load and use the shader 35

36 Effect Framework What is Effect Framework A shader is not enough We need to set/hold some states and structures to control/set/run shaders This can be done manually, depends on usage Effect framework does this abstraction/management In other platforms/APIs you need to use or write something similar 36

37 Effect Structure Structure of An Effect An effect file is a text file with a *.fx extension. It is split into three main sections: Variable declarations - these are values that can be set before rendering and then used in this effect file. Examples include: textures, world matrix, lighting parameters Techniques & Passes- defines how something is to be rendered. It includes state information along with vertex and shader declarations.state Functions - the shader code written in HLSLHLSL 37

38 Effect Structure (Variable/Parameters) Effect Parameters Parameters are defined at the start of the effect file. You must specify a type and an id (a unique name). You can then provide specific values depending on the type specifying the usage, user defined data and initial values. Examples float4 Diffuse : DIFFUSE = { 0, 0, 0, 1 }; float4 is the type (this must be one of the HLSL shader types), Diffuse is the name, the unique id. After the colon is a tag specifying the usage, in this case it is to be used as a diffuse colour. Finally the value is initialised to 0,0,0,1 (red, green, blue, alpha). float4x4 World : WORLD; float4x4 View : VIEW; float4x4 Projection : PROJECTION; The above declares three parameters with ids: World, View and Projection that will be used to set the world, view and projection matrix to be used during this effect file. Parameters can be read from and written to at run time by the application. More about how to do this later. 38

39 Effect Structure (Techniques) Techniques Within the technique you can define the passes which contain the actual state assignments. So an example of two techniques, the second having two passes, could be: technique FirstTechnique { pass P0 { // Set states here for pass 0 } } technique SecondTechnique { pass P0 { // Set states here for pass 0 } pass P1 { // Set states here for pass 1 } } 39

40 Effect Structure (States) States You can set states to values or expressions. They are set in a very similar way to normal Direct3D code (as shown in the states notes). E.g. in your code you might write:states gDevice->SetTextureStageState(0,D3DTSS_COLOROP,D3DTOP_SELECTARG1); but in the effect file the same thing is achieved by writing: ColorOp[0]=SelectArg1; Other examples: Lighting = true; // turn on lighting LightEnable[0] = true; // turn on light ZEnable = true; // turn on depth tests 40

41 Effect Structure (Functions) Functions The above examples did not include any shader code. We could if we wanted place the assembly shader code directly into the pass e.g.: VertexShader = asm { vs_1_1 m4x4 oPos, v0, c4 // pos in screen space. }; Most people now prefer using a high level shader language like HLSL to write their shaders in 'C' like code. Within the effect file we can write this code in a function just like we would write any shader code. We then specify the use of this shader in a technique pass e.g. VertexShader = compile vs_1_1 OurShaderName(); 41

42 Effects (Setting Parameters) Setting Parameters from Application pEffect->SetTexture("t0",texture1); pEffect->SetMatrix("world",&worldMatrix); pEffect->SetMatrix("camera",&viewMatrix); pEffect->SetVector("var1", v); 42

43 Effects (Rendering) Rendering an effect m_pEffect->SetTechnique ( “DiffuseMap” ) ; UINT nPassCount ; m_pEffect->Begin ( &nPassCount, 0 ) ; for ( UINT nPass = 0 ; nPass < nPassCount ; nPass++ ) { m_pEffect->BeginPass ( nPass ) ; // Do your draw code (DrawPrimitive) //... m_pEffect->EndPass () ; } m_pEffect->End () ; 43

44 Effect Demo (In VS) 44

45 Tools (Shader Authoring) Shader Authoring Node based (not so good) – ShaderFX (3dsmax) – Shader Fustion (Unity) – Most game engines own one » Artists like this style » Easier » Needs no programming knowledge » Needs no graphics math » Results in complex and un-optimized shaders Traditional Style (not visual) – RenderMonkey (ATI/AMD) – FXComposer (NVidia) – Your IDE texteditot or any other! – 3dsmax also has support for material shaders » Graphics Programmers like this » Difficult » Needs lots of math/programming knowledge » More optimized and specific shader code compared to the node based 45

46 Tools (Content Authoring) Shader Based Content Authoring Shaders alone are not enough You must be able to assign them to objects 3dsmax/maya support shader materials This is great, enables you to preview results while modeling Content interchange is also important Content interchange needs support both in your content authoting tool and the model interchange format (.fbx,.collada,.x, etc.) Most game engines have problems on this (bad) Many model file formats do not support shader or their support is provided via some extension to the base format (bad) 46

47 Tools (Debugging/Profiling) Shader Debugging Tools Debugging is an essential part of programming Lack of debugging makes development a cumbersome time –consuming task Without this you can debug a shader by visualizing outputs! Tools are getting betters on this NVidia nSight, which integrates to Visual Studio AMD ShaderAnalayser, which is used to optimize shader code AMD PerfStudio, is used to debug, profile shaders NVidia PerfKit, is used to debug/profile shaders NVidia Shader Debugger, is used to debug shaders The new Microsoft Visual Studio Graphics Debugger, used to debug hlsl code inside Visual Studio ! 47

48 Recommended Reading 48

49 Which topics do you prefer to be discussed in the next shader workshop?

50 Questions?

51

52 The End


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