struct Material { vec4 diffuse,emissive,specular; vec4 parameters; }; struct Light { vec3 direction; vec3 color; }; uniform int nlights; uniform Light lights[max(Nlights,1)]; uniform MaterialBuffer { Material Materials[Nmaterials]; }; #ifdef NORMAL #ifndef ORTHOGRAPHIC in vec3 ViewPosition; #endif in vec3 Normal; vec3 normal; #endif #ifdef COLOR in vec4 Color; #endif flat in int materialIndex; out vec4 outColor; // PBR material parameters vec3 Diffuse; // Diffuse for nonmetals, reflectance for metals. vec3 Specular; // Specular tint for nonmetals float Metallic; // Metallic/Nonmetals parameter float Fresnel0; // Fresnel at zero for nonmetals float Roughness2; // roughness squared, for smoothing #ifdef ENABLE_TEXTURE uniform sampler2D environmentMap; const float PI=acos(-1.0); const float twopi=2*PI; const float halfpi=PI/2; const int numSamples=7; // (x,y,z) -> (r,theta,phi); // theta -> [0,\pi]: colatitude // phi -> [0, 2\pi]: longitude vec3 cart2sphere(vec3 cart) { float x=cart.z; float y=cart.x; float z=cart.y; float r=length(cart); float phi=atan(y,x); float theta=acos(z/r); return vec3(r,phi,theta); } vec2 normalizedAngle(vec3 cartVec) { vec3 sphericalVec=cart2sphere(cartVec); sphericalVec.y=sphericalVec.y/(2*PI)-0.25; sphericalVec.z=sphericalVec.z/PI; return sphericalVec.yz; } #endif #ifdef NORMAL // h is the halfway vector between normal and light direction // GGX Trowbridge-Reitz Approximation float NDF_TRG(vec3 h) { float ndoth=max(dot(normal,h),0.0); float alpha2=Roughness2*Roughness2; float denom=ndoth*ndoth*(alpha2-1.0)+1.0; return denom != 0.0 ? alpha2/(denom*denom) : 0.0; } float GGX_Geom(vec3 v) { float ndotv=max(dot(v,normal),0.0); float ap=1.0+Roughness2; float k=0.125*ap*ap; return ndotv/((ndotv*(1.0-k))+k); } float Geom(vec3 v, vec3 l) { return GGX_Geom(v)*GGX_Geom(l); } // Schlick's approximation float Fresnel(vec3 h, vec3 v, float fresnel0) { float a=1.0-max(dot(h,v),0.0); float b=a*a; return fresnel0+(1.0-fresnel0)*b*b*a; } vec3 BRDF(vec3 viewDirection, vec3 lightDirection) { vec3 lambertian=Diffuse; // Cook-Torrance model vec3 h=normalize(lightDirection+viewDirection); float omegain=max(dot(viewDirection,normal),0.0); float omegaln=max(dot(lightDirection,normal),0.0); float D=NDF_TRG(h); float G=Geom(viewDirection,lightDirection); float F=Fresnel(h,viewDirection,Fresnel0); float denom=4.0*omegain*omegaln; float rawReflectance=denom > 0.0 ? (D*G)/denom : 0.0; vec3 dielectric=mix(lambertian,rawReflectance*Specular,F); vec3 metal=rawReflectance*Diffuse; return mix(dielectric,metal,Metallic); } #endif void main() { vec4 diffuse; vec4 emissive; Material m; #ifdef TRANSPARENT m=Materials[abs(materialIndex)-1]; emissive=m.emissive; if(materialIndex >= 0) diffuse=m.diffuse; else { diffuse=Color; #if Nlights == 0 emissive += Color; #endif } #else m=Materials[int(materialIndex)]; emissive=m.emissive; #ifdef COLOR diffuse=Color; #if Nlights == 0 emissive += Color; #endif #else diffuse=m.diffuse; #endif #endif #if defined(NORMAL) && Nlights > 0 Specular=m.specular.rgb; vec4 parameters=m.parameters; Roughness2=1.0-parameters[0]; Roughness2=Roughness2*Roughness2; Metallic=parameters[1]; Fresnel0=parameters[2]; Diffuse=diffuse.rgb; // Given a point x and direction \omega, // L_i=\int_{\Omega}f(x,\omega_i,\omega) L(x,\omega_i)(\hat{n}\cdot \omega_i) // d\omega_i, where \Omega is the hemisphere covering a point, // f is the BRDF function, L is the radiance from a given angle and position. normal=normalize(Normal); normal=gl_FrontFacing ? normal : -normal; #ifdef ORTHOGRAPHIC vec3 viewDir=vec3(0.0,0.0,1.0); #else vec3 viewDir=-normalize(ViewPosition); #endif // For a finite point light, the rendering equation simplifies. vec3 color=emissive.rgb; for(int i=0; i < nlights; ++i) { Light Li=lights[i]; vec3 L=Li.direction; float cosTheta=max(dot(normal,L),0.0); // $\omega_i \cdot n$ term vec3 radiance=cosTheta*Li.color; color += BRDF(viewDir,L)*radiance; } #if defined(ENABLE_TEXTURE) && !defined(COLOR) // Experimental environment radiance using Riemann sums; // can also do importance sampling. vec3 envRadiance=vec3(0.0,0.0,0.0); vec3 normalPerp=vec3(-normal.y,normal.x,0.0); if(length(normalPerp) == 0.0) normalPerp=vec3(1.0,0.0,0.0); // we now have a normal basis; normalPerp=normalize(normalPerp); vec3 normalPerp2=normalize(cross(normal,normalPerp)); const float step=1.0/numSamples; const float phistep=twopi*step; const float thetastep=halfpi*step; for (int iphi=0; iphi < numSamples; ++iphi) { float phi=iphi*phistep; for (int itheta=0; itheta < numSamples; ++itheta) { float theta=itheta*thetastep; vec3 azimuth=cos(phi)*normalPerp+sin(phi)*normalPerp2; vec3 L=sin(theta)*azimuth+cos(theta)*normal; vec3 rawRadiance=texture(environmentMap,normalizedAngle(L)).rgb; vec3 surfRefl=BRDF(Z,L); envRadiance += surfRefl*rawRadiance*sin(2.0*theta); } } envRadiance *= halfpi*step*step; color += envRadiance.rgb; #endif outColor=vec4(color,diffuse.a); #else outColor=emissive; #endif }