Shader Programming CgFX, OpenGL 2.0 Michael Haller 2003
Outline What is CgFX? CgFX runtime Production pipeline with CgFX CgFX Tools set OpenGL 2.0
What is CgFX? CgFX (C for Graphics Effekt File) Supports Microsoft.fx files Cg plus: Multi-pass Hardware fallbacks (techniques) Complete Hardware states Tweakables MS.fx (HLSL) plus: DirectX8 and OpenGL MAC and Linux
CgFX overview
Typical Production Pipeline Programmers write assembly for different hardware DCC tool (Maya, Max, SoftImage, ) Digital Content Creation Scene exporter plug-in Artists create models, textures, maps, in DCC tool of choice DCC Image ASM Shaders (HW1) ASM Shaders (HW2) Scene manager Models, Textures, Maps, Application (game, renderer, ) Not the same! Game Image App Scene Manager hard-coded to choose at run-time the appropriate ASM shaders + state for the hardware
CgFX Production Pipeline Programmers and/or artists write FX effects DCC tool (Maya, Max, SoftImage, ) FX material plug-in Scene exporter plug-in Artists assign FX files to scene objects and tweak parameters for each object in real-time FX files Models, Textures, Maps, FX effects + parameters Same Image Scene manager FX runtime Application (game, renderer, ) For any FX, App Scene Manager chooses at run-time the appropriate technique for the hardware
CgFX Example File - Structure Global declarations Tweakable declarations Vertex shaders Fragment shaders Techniques to encapsulate shaders
Techniques effect myeffectname { technique PixelShaderVersion { }; technique FixedFunctionVersion { }; technique LowDetailVersion { }; };
Passes Each technique contains one or more passes Each pass may contain a vertex program, a fragment program, or both. E.g. Pass 0: Fixed-function pixel processing to output the ambient color. Pass 1: ps_1_1 fragment program Pass 2: ps_2_0 fragment program Typically, all passes of a technique use Cg or assembly programs.
Render States pass firstpass { DepthWriteEnable = true; AlphaBlendEnable = false; MinFilter[ 0 ] = Linear; MagFilter[ 0 ] = Linear; MipFilter[ 0 ] = Linear; // Pixel shader written in assembly PixelShader = asm { ps.1.1 tex t0; mov r0, t0; }; };
Variables and Semantics Global and per-technique Cg-style variables (passed as uniform parameters): bool AlphaBlending = false; float bumpheight = 0.5f; These variables can contain a user-defined semantic, which helps applications provide the correct data to the shader: float4x4 myviewmatrix : ViewMatrix; texture2d sometexture : DiffuseMap;
Annotations Additionally, each variable can have an optional annotation. An annotation describes a user interface element for manipulating uniform variables: float bumpheight < string gui = slider ; float uimin = 0.0f; float uimax = 1.0f; float uistep = 0.1f; > = 0.5f;
My first fx example (Blinn) struct appdata { float4 vposition : POSITION; float4 vnormal : NORMAL; float4 vtexcoords : TEXCOORD0; }; struct vpconn { float4 vtexcoord0 : TEXCOORD0; float4 vdiffuse : COLOR0; float4 vposition : POSITION; float4 vspecular : COLOR1; };
My first fx example (Blinn) II // un-tweakables float4x4 worldview : WorldView; float4x4 worldviewit: WorldViewIT; float4x4 worldviewprojection : WorldViewProjection; [...] // tweakables float4 diffuse : DIFFUSE = { 0.1f, 0.1f, 0.5f, 1.0f }; [...] float4 lightpos : Position < string Object = "PointLight"; string Space = "World"; > = {100.0f, 100.0f, 100.0f, 0.0f};
My first fx example (Blinn) III vpconn vs_blinnshading(appdata IN, uniform float4x4 ModelViewProj, uniform float4x4 ModelView, uniform float4x4 ModelViewIT, uniform float4x4 ViewIT, uniform float4x4 View, uniform float4 lightpos, uniform float4 diffuse, uniform float4 specular, uniform float4 ambient) { vpconn OUT; [ ] } OUT.vDiffuse = diff_term; OUT.vPosition = mul(modelviewproj,in.vposition); return OUT;
My first fx example (Blinn) IV technique Blinn { pass p0 { Zenable = true; ZWriteEnable = true; CullMode = None; VertexShader = compile vs_1_1 vs_blinnshading( worldviewprojection, worldview, worldviewit, viewit, view, lightpos, diffuse, specular, ambient); } }
Results (Blinn) I
Results (Blinn) II
Production Pipeline with CgFX
CgFX Tools Set Integrated authoring in DCC apps: 3ds MAX 5.1 MAYA 4.5 XSI (CgFX Coming soon...) NVB Exporter CgFX Viewer OpenGL ARB, DirectX8, DirectX9
3D Studio Max 5.1 stdmaterial <-> CgFX Ability to select MAX scene lights and connect them to.fx parameters On the fly editing of shaders and auto-update of.fx GUI MAXSCRIPT support Source Code
Integration in 3D Studio Max
CgFX Viewport Manager Intuitive artist controls (sliders, color pickers, etc.) Dynamic, shaderspecific GUI Multiple Techniques for fallbacks Supports.fx file format
Shader changed by selecting a new fx file Color and numeric values can be changed Customizable Parameters are specific to each effect Bitmaps can be swapped
NVB Exporter for 3ds max Based on Pierre Terdiman s 3ds max exporter http://www.codercorner.com/flexporter.htm Exports Scene data Mesh, materials, lights, camera, skinning, etc... Exports CgFX materials ICgFXDataBridge interface Source code
CgFX Viewer Scene graph GUI.fx parameters edition Error reporting for easy.fx file problem identification Runs OpenGL, DirectX8, DirectX9 Switch between devices at any point
CgFX Viewer II Main Application Window Connection Editor Window The CgFX Viewer can be used as a production resource and a code example for implementing CgFX
How Does CgFX relate to Cg? CgFX describes an entire effect Cg implements a particular function required by an effect CgFX describes all the parameters (and their meaning or semantics) that the app has to provide automatic parameter discovery CgFX can describe complex multi-pass effects CgFX can handle multiple techniques
Hardware Shader Workflow Designing Shaders and Using Existing Shaders Artist-Configurable Parameters Editing Shader Parameters Exporting Shader Parameters to Game Engine
Multiple, narrowly-targeted shaders are more efficient/faster than large all-purpose shaders Several shaders may share similar features and lighting models Small Efficient Shaders
OpenGL: Where do you want to go today?
OpenGL 2.0 Goals Reduce the need for existing and future extensions to OpenGL by replacing complexity with programmability. Backward compatibility to OpenGL 1.x Address the needs of dynamic media authoring and playback applications needed by OpenML.
Status of Shading Language Extensions to support the OpenGL Shading Language Language approved as ARB extensions in June 2003 Language and extensions expected to be rolled into OpenGL in 6 rolled into OpenGL in 6-12 months 12 months That version of OpenGL will be called OpenGL 2.0 It will still be backwards compatible with 1.0-1.5 3Dlabs is shipping a preliminary implementation
Overview
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