Spherical harmonic shader opengl es

라이팅 모델에 대한 리서치가 많아서리... 리얼타임 렌더링 3판에서 잠시 소개 된 구면 조화 라이팅 모델의 임베디드 타입 이다. 버택스 쉐이더 Sh.vsh

  //Spherical harmonic shader opengl es //Sh.vsh //------------------------------<wbr />---------- attribute vec4 Position; attribute vec3 Normal; attribute vec3 DiffuseMaterial; varying vec3 EyespaceNormal; varying vec3 EyespaceLight; varying vec4 VertexPosition; varying vec3 Diffuse; varying vec3 Irrad; uniform vec3 LightPosition; uniform mat4 Projection; uniform mat4 Modelview; uniform mat3 NormalMatrix; const vec3 L_00 = vec3( 0.79, 0.44, 0.54); const vec3 L_1_1 = vec3( 0.39, 0.35, 0.60); const vec3 L_10 = vec3(-0.34, -0.18, -0.27); const vec3 L_11 = vec3(-0.29, -0.06, 0.01); const vec3 L_2_2 = vec3(-0.11, -0.05, -0.12); const vec3 L_2_1 = vec3(-0.26, -0.22, -0.45); const vec3 L_20 = vec3(-0.16, -0.09, -0.15); const vec3 L_21 = vec3( 0.56, 0.21, 0.14); const vec3 L_22 = vec3( 0.21, -0.05, -0.30); vec3 irradcoeffs(vec3 L00, vec3 L1_1, vec3 L10, vec3 L11, vec3 L2_2, vec3 L2_1, vec3 L20, vec3 L21, vec3 L22, vec3 n) { float x2, y2, z2; float xy, yz, xz; float x, y, z; const float c1 = 0.429043; const float c2 = 0.511664; const float c3 = 0.743125; const float c4 = 0.886227; const float c5 = 0.247708; x = n.x; y = n.y; z = n.z; x2 = x*x ; y2 = y*y ; z2 = z*z ; xy = x*y ; yz = y*z ; xz = x*z ; return c1*L22*(x2-y2) + c3*L20*z2 + c4*L00 - c5*L20 + 2.0*c1*(L2_2*xy + L21*xz + L2_1*yz) + 2.0*c2*(L11*x+L1_1*y+L10*z); } void main(void) { EyespaceNormal = NormalMatrix * Normal; Irrad = irradcoeffs(L_00, L_1_1, L_10, L_11, L_2_2, L_2_1, L_20, L_21, L_22, normalize(Normal)); Diffuse = DiffuseMaterial; gl_Position = Projection * Modelview * Position; EyespaceLight = normalize(LightPosition - vec3(gl_Position)); }



 프라그먼트 쉐이더 Sh.fsh

  //Sh.fsh varying mediump vec3 EyespaceNormal; varying mediump vec3 EyespaceLight; varying lowp vec3 Diffuse; varying lowp vec3 Irrad; uniform highp vec3 Ambient; uniform highp vec3 Specular; uniform highp float Shininess; void main(void) { highp vec3 N = normalize(EyespaceNormal); highp vec3 L = normalize(EyespaceLight); highp vec3 E = vec3(0, 0, 1); highp vec3 H = normalize(L + E); highp float df = max(0.0, dot(N, L)); highp float sf = max(0.0, dot(N, H)); sf = pow(sf, Shininess); highp vec3 color = df * Irrad + sf * Specular; gl_FragColor = vec4(color, 1); }

유니티 SH 디버그 쉐이더 링크.
http://forum.unity3d.com/threads/156019-Spherical-Harmonic-Debug-Shader

Shader "Spherical Harmonic" { Properties { _SHAr ("First Order Harmonic", Vector) = (0.0,0.0,0.0,0.0) _SHAg ("First Order Harmonic", Vector) = (0.0,0.0,0.0,0.0) _SHAb ("First Order Harmonic", Vector) = (0.0,0.0,0.0,0.0) _SHBr ("Second Order Harmonic", Vector) = (0.0,0.0,0.0,0.0) _SHBg ("Second Order Harmonic", Vector) = (0.0,0.0,0.0,0.0) _SHBb ("Second Order Harmonic", Vector) = (0.0,0.0,0.0,0.0) _SHC ("Third OrderHarmonic", Vector) = (0.0,0.0,0.0,0.0) _A ("Alpha", Float) = 0.5 } SubShader { Tags { "Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent" } Blend SrcAlpha OneMinusSrcAlpha Cull Off Lighting Off ZWrite On Pass{ CGPROGRAM #pragma vertex vert #pragma fragment frag #pragma exclude_renderers #pragma target 2.0 #include "UnityCG.cginc" #include "Lighting.cginc" uniform float4 _SHAr; uniform float4 _SHAg; uniform float4 _SHAb; uniform float4 _SHBr; uniform float4 _SHBg; uniform float4 _SHBb; uniform float4 _SHC; uniform float _A; struct appdata_t { float4 vertex : POSITION; fixed4 color : COLOR; float3 normal : TEXCOORD0; float4 tangent : TEXCOORD1; }; struct v2f { float4 pos : SV_POSITION; fixed4 color : COLOR; }; v2f vert (appdata_t v) { v2f o; UNITY_DIRBASIS; //This is the spherical harmonic lookup, it takes in the world normal and spits out the appropriate value in that direction //It comes from appendix 10 of Peter Pike Sloan's paper "Stupid Spherical Harmonic Tricks" //It's a bit more complex than the simpliest transform so it can be more efficient //http://www.ppsloan.org/publications/StupidSH36.pdf //It takes 12 coefficients (the numbers in the _SHA,_SHB and _SHC vectors) multiplies them against eachother to construct the harmonic //Each coefficient represents a cosine wave (which in turn are used to describe the sphere, axis by axis) //Each level _SHA - _SHB etc divides the sphere into two sub spheres, and each contains more detail (higher frequency data) about the final wave/sphere //It can be thought of as sound //Each seperate frequency is a different pitch, and the final sound is all these pieces blended together float4 wN = v.vertex; //Here I'm using the vertex position since this is for a sphere around the origin //It's very similar to a fourier transform, but across the surface of a sphere half3 x1, x2, x3; // Linear + constant polynomial terms x1.r = dot(_SHAr,wN); x1.g = dot(_SHAg,wN); x1.b = dot(_SHAb,wN); // 4 of the quadratic polynomials half4 vB = wN.xyzz * wN.yzzx; x2.r = dot(_SHBr,vB); x2.g = dot(_SHBg,vB); x2.b = dot(_SHBb,vB); // Final quadratic polynomial float vC = wN.x*wN.x - wN.y*wN.y; x3 = _SHC.rgb * vC; float3 shC = x1 + x2 + x3; //Setup the vertices o.pos = mul(UNITY_MATRIX_MVP, v.vertex); //the vectors the rgba colors also work as xyzw in space (color is a space, afterall...) //i.e. positive and negative red translates verts left and right along the x axis //o.pos = mul(UNITY_MATRIX_MVP, float4(shC.rgb, 1.0f)); //Comment this in to see the shape of the spherical harmonic //Set the out color //o.color = float4(mul(shC, unity_DirBasis), _A); //What was I doing with this?! :O o.color = float4(shC, _A); return o; } fixed4 frag (v2f i) : COLOR { float4 c = float4(1.0f,1.0f,1.0f,1.0f); return i.color; } ENDCG } } }

Other Link.
http://www.paulsprojects.net/opengl/sh/sh.html

Spherical harmonics

http://ko.wikipedia.org/wiki/%EA%B5%AC%EB%A9%B4_%EC%A1%B0%ED%99%94_%ED%95%A8%EC%88%98



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