Lecture 10: Environment and Bump MappingProf. Aaron LantermanSchool of Electrical and Computer EngineeringGeorgia Institute of TechnologyReal-time graphics has come a long wayVirtua Virtua FighterFighter(SEGA Corporation)(SEGA Corporation)NV1NV150K triangles/sec50K triangles/sec1M pixel ops/sec1M pixel ops/sec19951995Dead or Alive 3Dead or Alive 3((Tecmo Tecmo Corporation)Corporation)Xbox (NV2A)Xbox (NV2A)100M triangles/sec100M triangles/sec1G pixel ops/sec1G pixel ops/sec20012001DawnDawn(NVIDIA Corporation)(NVIDIA Corporation)GeForce FX (NV30)GeForce FX (NV30)200M triangles/sec200M triangles/sec2G pixel ops/sec2G pixel ops/sec20032003Slide from from “Teaching Cg” Powerpoint presentation:developer.nvidia.com/object/cg_tutorial_teaching.htmlThe Cg Tutorial• Can get Cg Toolkit, example code, etc. here:http://developer.nvidia.com/object/cg_tutorial_home.htmlImage from “Teaching Cg” Powerpoint presentation:developer.nvidia.com/object/cg_tutorial_teaching.htmlNice framework for experimentationImage from “Teaching Cg” Powerpoint presentation:developer.nvidia.com/object/cg_tutorial_teaching.htmlCube mapsImages from “OpenGL Cube Map Texturing,”developer.nvidia.com/object/cube_map_ogl_tutorial.htmlBack FrontRightBottom Left ToptexCUBE((samplerCUBE) envMap,(float3) vec)Reflection and refraction θI θR θI θTIncidentvector IRefractedvector TIncidentvector IReflectedvector RNormalvector NNormalvector N θI=θR η1sin(θI) =η2sin(θT)T=refract(I,N,etaRatio)R=reflect(I,N) η1/η2etaRatio= η1 η2Cg vertex shader for reflective mappingvoid C7E1v_reflection(float4 position : POSITION, float2 texCoord : TEXCOORD0, float3 normal : NORMAL, out float4 oPosition : POSITION, out float2 oTexCoord : TEXCOORD0, out float3 R : TEXCOORD1,uniform float3 eyePositionW,uniform float4x4 modelViewProj, uniform float4x4 modelToWorld){ oPosition = mul(modelViewProj, position); oTexCoord = texCoord; // Compute position and normal in world space float3 positionW = mul(modelToWorld, position).xyz; float3 N = mul((float3x3)modelToWorld, normal); N = normalize(N); // Compute the incident and reflected vectors float3 I = positionW - eyePositionW; R = reflect(I, N);}From “The Cg Tutorial,” p. 177Cg pixel shader for reflective mappingvoid C7E2f_reflection(float2 texCoord : TEXCOORD0, float3 R : TEXCOORD1, out float4 color : COLOR, uniform float reflectivity, uniform sampler2D decalMap, uniform samplerCUBE environmentMap){ // Fetch reflected environment color float4 reflectedColor = texCUBE(environmentMap, R); // Fetch the decal base color float4 decalColor = tex2D(decalMap, texCoord); color = lerp(decalColor, reflectedColor, reflectivity);}From “The Cg Tutorial,” p. 180Different indices of refractionAround water (1.333)0.8Images from Thomas Kerwin, “Refraction in OpenGL,”www.cse.ohio-state.edu/~kerwin/refraction.htmlVacuum: 1.0Air: 1.0003Water: 1.333Glass: 1.5 (ordinary window glass)Plastic: 1.5Diamond: 2.417Data from “The Cg Tutorial,” p. 184Cg vertex shader for refractive mappingvoid C7E3v_refraction(float4 position : POSITION, float2 texCoord : TEXCOORD0, float3 normal : NORMAL, out float4 oPosition : POSITION, out float2 oTexCoord : TEXCOORD0, out float3 T : TEXCOORD1, uniform float etaRatio, uniform float3 eyePositionW, uniform float4x4 modelViewProj, uniform float4x4 modelToWorld){ oPosition = mul(modelViewProj, position); oTexCoord = texCoord; // Compute position and normal in world space float3 positionW = mul(modelToWorld, position).xyz; float3 N = mul((float3x3)modelToWorld, normal); N = normalize(N); // Compute the incident and refracted vectors float3 I = positionW - eyePositionW; T = refract(I, N, etaRatio);}From “The Cg Tutorial,” p. 187Cg pixel shader for refractive mappingvoid C7E4f_refraction(float2 texCoord : TEXCOORD0, float3 T : TEXCOORD1, out float4 color : COLOR, uniform float transmittance, uniform sampler2D decalMap, uniform samplerCUBE environmentMap){ // Fetch the decal base color float4 decalColor = tex2D(decalMap, texCoord); // Fetch refracted environment color float4 refractedColor = texCUBE(environmentMap, T); // Compute the final color color = lerp(decalColor, refractedColor, transmittance);}From “The Cg Tutorial,” p. 188Chromatic dispersion θIRefractedvectorsIncidentvector INormalvector NT blueT redT greenWithout CDWith CDImages from Thomas Kerwin, “Refraction in OpenGL,”www.cse.ohio-state.edu/~kerwin/refraction.htmlFresnel effect reflectCoeff = max(0,min(1,bias + scale(1 + I • N)power)) Cfinal= reflectCoeff × Creflected+ (1− reflectCoeff )Crefracted• Some light reflects and some refracts• Think about looking into water– At shallow angles, a lot of reflection and little refraction– Looking straight in, a lot of refraction and a little reflection• Empirical approximation:From “The Cg Tutorial,” p. 189Bump mappingDrawing from Søren Dreijer, “Bump Mapping Using Cg (3rd Edition),”www.blacksmith-studios.dk/projects/downloads/bumpmapping_using_cg.phpImages from Paul Baker, “Simple Bumpmapping,”www.paulsprojects.net/tutorials/simplebump/simplebump.htmlBump mapping examplesHeight mapNormal mapTop row from Wikipediaentry on “bump mapping”Bottom row from Søren Dreijer, “Bump Mapping Using Cg (3rd Edition),”www.blacksmith-studios.dk/projects/downloads/bumpmapping_using_cg.phpShader effect movies• Bump mapping demo with the Cimg libraryhttp://video.google.com/videoplay?docid=1570416667092534064• Bump mapping and reflective textures– (HLEH - Half Life mod???)http://www.youtube.com/watch?v=FmpyHc6hXc4• Bump mapping on the Nintendo DShttp://www.youtube.com/watch?v=6ypt5JE-ofgStoring normals in textures• Textures don’t have to store color; we can storeother things as well, like normals– Use r, g, b components to store, x, y, z of normal• Problem: Textures take [0,1] values; normalsneed [-1,1] values• Easy solution: “Range Compression”colorComponent = 0.5 * normalComponent + 0.5;normalComponent = 2 * (colorComponent - 0.5);From “The Cg Tutorial,” p. 202Creating normal map from height field• Height field H(u,v) normal =Hg− Hr,Hg− Ha,1( )Hg− Hr,Hg− Ha,1( ) Hg Hr Ha• In flat regions, normal is (0,0,1), i.e. pointing “up”From “The Cg Tutorial,” p. 203Cg vertex shader for bump mappingvoid C8E1v_bumpWall(float4 position : POSITION, float2 texCoord : TEXCOORD0, out float4
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