#include "Macros.fxh" #define NORMALS #define UV // A constant buffer that stores the three basic column-major matrices for composing geometry. cbuffer ModelViewProjectionConstantBuffer : register(b0) { matrix model; matrix view; matrix projection; }; // Per-vertex data used as input to the vertex shader. struct VertexShaderInput { float4 position : POSITION; #ifdef NORMALS float3 normal : NORMAL; #endif #ifdef UV float2 texcoord : TEXCOORD0; #endif }; // Per-pixel color data passed through the pixel shader. struct PixelShaderInput { float4 position : SV_POSITION; float3 poswithoutw : POSITION1; #ifdef NORMALS float3 normal : NORMAL; #endif float2 texcoord : TEXCOORD0; }; PixelShaderInput main_vs(VertexShaderInput input) { PixelShaderInput output; // Transform the vertex position into projected space. float4 pos = mul(input.position, model); output.poswithoutw = float3(pos.xyz) / pos.w; #ifdef NORMALS // If we have normals... output.normal = normalize(mul(float4(input.normal.xyz, 0.0), model)); #endif #ifdef UV output.texcoord = input.texcoord; #else output.texcoord = float2(0.0f, 0.0f); #endif #ifdef HAS_NORMALS #ifdef HAS_TANGENTS vec3 normalW = normalize(vec3(u_ModelMatrix * vec4(a_Normal.xyz, 0.0))); vec3 tangentW = normalize(vec3(u_ModelMatrix * vec4(a_Tangent.xyz, 0.0))); vec3 bitangentW = cross(normalW, tangentW) * a_Tangent.w; v_TBN = mat3(tangentW, bitangentW, normalW); #else // HAS_TANGENTS != 1 v_Normal = normalize(vec3(u_ModelMatrix * vec4(a_Normal.xyz, 0.0))); #endif #endif // Transform the vertex position into projected space. pos = mul(pos, view); pos = mul(pos, projection); output.position = pos; return output; } // // This fragment shader defines a reference implementation for Physically Based Shading of // a microfacet surface material defined by a glTF model. // // References: // [1] Real Shading in Unreal Engine 4 // http://blog.selfshadow.com/publications/s2013-shading-course/karis/s2013_pbs_epic_notes_v2.pdf // [2] Physically Based Shading at Disney // http://blog.selfshadow.com/publications/s2012-shading-course/burley/s2012_pbs_disney_brdf_notes_v3.pdf // [3] README.md - Environment Maps // https://github.com/KhronosGroup/glTF-WebGL-PBR/#environment-maps // [4] "An Inexpensive BRDF Model for Physically based Rendering" by Christophe Schlick // https://www.cs.virginia.edu/~jdl/bib/appearance/analytic%20models/schlick94b.pdf #define NORMALS #define UV #define HAS_NORMALS // #define USE_IBL #define USE_TEX_LOD DECLARE_TEXTURE(baseColourTexture, 0); DECLARE_TEXTURE(normalTexture, 1); DECLARE_TEXTURE(emissionTexture, 2); DECLARE_TEXTURE(occlusionTexture, 3); DECLARE_TEXTURE(metallicRoughnessTexture, 4); DECLARE_CUBEMAP(envDiffuseTexture, 8); DECLARE_TEXTURE(brdfLutTexture, 9); DECLARE_CUBEMAP(envSpecularTexture, 10); cbuffer cbPerFrame : register(b0) { float3 lightDir; float3 lightColour; }; cbuffer cbPerObject : register(b1) { float normalScale; float3 emissiveFactor; float occlusionStrength; float2 metallicRoughnessValues; float4 baseColorFactor; float3 camera; // debugging flags used for shader output of intermediate PBR variables float4 scaleDiffBaseMR; float4 scaleFGDSpec; float4 scaleIBLAmbient; }; #ifdef HAS_NORMALS #ifdef HAS_TANGENTS varying mat3 v_TBN; #else #endif #endif // Encapsulate the various inputs used by the various functions in the shading equation // We store values in this struct to simplify the integration of alternative implementations // of the shading terms, outlined in the Readme.MD Appendix. struct PBRInfo { float NdotL; // cos angle between normal and light direction float NdotV; // cos angle between normal and view direction float NdotH; // cos angle between normal and half vector float LdotH; // cos angle between light direction and half vector float VdotH; // cos angle between view direction and half vector float perceptualRoughness; // roughness value, as authored by the model creator (input to shader) float metalness; // metallic value at the surface float3 reflectance0; // full reflectance color (normal incidence angle) float3 reflectance90; // reflectance color at grazing angle float alphaRoughness; // roughness mapped to a more linear change in the roughness (proposed by [2]) float3 diffuseColor; // color contribution from diffuse lighting float3 specularColor; // color contribution from specular lighting }; static const float M_PI = 3.141592653589793; static const float c_MinRoughness = 0.04; float4 SRGBtoLINEAR(float4 srgbIn) { #ifdef MANUAL_SRGB #ifdef SRGB_FAST_APPROXIMATION float3 linOut = pow(srgbIn.xyz,float3(2.2, 2.2, 2.2)); #else //SRGB_FAST_APPROXIMATION float3 bLess = step(float3(0.04045, 0.04045, 0.04045), srgbIn.xyz); float3 linOut = lerp(srgbIn.xyz / float3(12.92, 12.92, 12.92), pow((srgbIn.xyz + float3(0.055, 0.055, 0.055)) / float3(1.055, 1.055, 1.055), float3(2.4, 2.4, 2.4)), bLess); #endif //SRGB_FAST_APPROXIMATION return float4(linOut,srgbIn.w);; #else //MANUAL_SRGB return srgbIn; #endif //MANUAL_SRGB } // Find the normal for this fragment, pulling either from a predefined normal map // or from the interpolated mesh normal and tangent attributes. float3 getNormal(float3 position, float3 normal, float2 uv) { // Retrieve the tangent space matrix #ifndef HAS_TANGENTS float3 pos_dx = ddx(position); float3 pos_dy = ddy(position); float3 tex_dx = ddx(float3(uv, 0.0)); float3 tex_dy = ddy(float3(uv, 0.0)); float3 t = (tex_dy.y * pos_dx - tex_dx.y * pos_dy) / (tex_dx.x * tex_dy.y - tex_dy.x * tex_dx.y); #ifdef HAS_NORMALS float3 ng = normalize(normal); #else float3 ng = cross(pos_dx, pos_dy); #endif t = normalize(t - ng * dot(ng, t)); float3 b = normalize(cross(ng, t)); row_major float3x3 tbn = float3x3(t, b, ng); #else // HAS_TANGENTS mat3 tbn = v_TBN; #endif #ifdef HAS_NORMALMAP float3 n = SAMPLE_TEXTURE(normalTexture, uv).rgb; // Need to check the multiplication is equivalent.. n = normalize(mul(((2.0 * n - 1.0) * float3(normalScale, normalScale, 1.0)), tbn)); #else float3 n = tbn[2].xyz; #endif return n; } #ifdef USE_IBL // Calculation of the lighting contribution from an optional Image Based Light source. // Precomputed Environment Maps are required uniform inputs and are computed as outlined in [1]. // See our README.md on Environment Maps [3] for additional discussion. float3 getIBLContribution(PBRInfo pbrInputs, float3 n, float3 reflection) { float mipCount = 9.0; // resolution of 512x512 float lod = (pbrInputs.perceptualRoughness * mipCount); // retrieve a scale and bias to F0. See [1], Figure 3 float2 val = float2(pbrInputs.NdotV, 1.0 - pbrInputs.perceptualRoughness); float3 brdf = SRGBtoLINEAR(SAMPLE_TEXTURE(brdfLutTexture, val)).rgb; float3 diffuseLight = SRGBtoLINEAR(SAMPLE_CUBEMAP(envDiffuseTexture, n)).rgb; #ifdef USE_TEX_LOD float4 reflectionWithLOD = float4(reflection, 0); float3 specularLight = SRGBtoLINEAR(SAMPLE_CUBEMAP_LOD(envSpecularTexture, reflectionWithLOD)).rgb; #else float3 specularLight = SRGBtoLINEAR(SAMPLE_CUBEMAP(envSpecularTexture, reflection)).rgb; #endif float3 diffuse = diffuseLight * pbrInputs.diffuseColor; float3 specular = specularLight * (pbrInputs.specularColor * brdf.x + brdf.y); // For presentation, this allows us to disable IBL terms diffuse *= scaleIBLAmbient.x; specular *= scaleIBLAmbient.y; return diffuse + specular; } #endif // Basic Lambertian diffuse // Implementation from Lambert's Photometria https://archive.org/details/lambertsphotome00lambgoog // See also [1], Equation 1 float3 diffuse(PBRInfo pbrInputs) { return pbrInputs.diffuseColor / M_PI; } // The following equation models the Fresnel reflectance term of the spec equation (aka F()) // Implementation of fresnel from [4], Equation 15 float3 specularReflection(PBRInfo pbrInputs) { return pbrInputs.reflectance0 + (pbrInputs.reflectance90 - pbrInputs.reflectance0) * pow(clamp(1.0 - pbrInputs.VdotH, 0.0, 1.0), 5.0); } // This calculates the specular geometric attenuation (aka G()), // where rougher material will reflect less light back to the viewer. // This implementation is based on [1] Equation 4, and we adopt their modifications to // alphaRoughness as input as originally proposed in [2]. float geometricOcclusion(PBRInfo pbrInputs) { float NdotL = pbrInputs.NdotL; float NdotV = pbrInputs.NdotV; float r = pbrInputs.alphaRoughness; float attenuationL = 2.0 * NdotL / (NdotL + sqrt(r * r + (1.0 - r * r) * (NdotL * NdotL))); float attenuationV = 2.0 * NdotV / (NdotV + sqrt(r * r + (1.0 - r * r) * (NdotV * NdotV))); return attenuationL * attenuationV; } // The following equation(s) model the distribution of microfacet normals across the area being drawn (aka D()) // Implementation from "Average Irregularity Representation of a Roughened Surface for Ray Reflection" by T. S. Trowbridge, and K. P. Reitz // Follows the distribution function recommended in the SIGGRAPH 2013 course notes from EPIC Games [1], Equation 3. float microfacetDistribution(PBRInfo pbrInputs) { float roughnessSq = pbrInputs.alphaRoughness * pbrInputs.alphaRoughness; float f = (pbrInputs.NdotH * roughnessSq - pbrInputs.NdotH) * pbrInputs.NdotH + 1.0; return roughnessSq / (M_PI * f * f); } float4 main_ps(PixelShaderInput input) : SV_TARGET { // Metallic and Roughness material properties are packed together // In glTF, these factors can be specified by fixed scalar values // or from a metallic-roughness map float perceptualRoughness = metallicRoughnessValues.y; float metallic = metallicRoughnessValues.x; #ifdef HAS_METALROUGHNESSMAP // Roughness is stored in the 'g' channel, metallic is stored in the 'b' channel. // This layout intentionally reserves the 'r' channel for (optional) occlusion map data float4 mrSample = SAMPLE_TEXTURE(metallicRoughnessTexture, input.texcoord); // Had to reverse the order of the channels here - TODO: investigate.. perceptualRoughness = mrSample.g * perceptualRoughness; metallic = mrSample.b * metallic; #endif perceptualRoughness = clamp(perceptualRoughness, c_MinRoughness, 1.0); metallic = clamp(metallic, 0.0, 1.0); // Roughness is authored as perceptual roughness; as is convention, // convert to material roughness by squaring the perceptual roughness [2]. float alphaRoughness = perceptualRoughness * perceptualRoughness; // The albedo may be defined from a base texture or a flat color #ifdef HAS_BASECOLORMAP float4 baseColor = SRGBtoLINEAR(SAMPLE_TEXTURE(baseColourTexture, input.texcoord)) * baseColorFactor; #else float4 baseColor = baseColorFactor; #endif float3 f0 = float3(0.04, 0.04, 0.04); float3 diffuseColor = baseColor.rgb * (float3(1.0, 1.0, 1.0) - f0); diffuseColor *= 1.0 - metallic; float3 specularColor = lerp(f0, baseColor.rgb, metallic); // Compute reflectance. float reflectance = max(max(specularColor.r, specularColor.g), specularColor.b); // For typical incident reflectance range (between 4% to 100%) set the grazing reflectance to 100% for typical fresnel effect. // For very low reflectance range on highly diffuse objects (below 4%), incrementally reduce grazing reflecance to 0%. float reflectance90 = clamp(reflectance * 25.0, 0.0, 1.0); float3 specularEnvironmentR0 = specularColor.rgb; float3 specularEnvironmentR90 = float3(1.0, 1.0, 1.0) * reflectance90; float3 n = getNormal(input.poswithoutw, input.normal, input.texcoord); // normal at surface point float3 v = normalize(camera - input.poswithoutw); // Vector from surface point to camera float3 l = normalize(lightDir); // Vector from surface point to light float3 h = normalize(l + v); // Half vector between both l and v float3 reflection = -normalize(reflect(v, n)); float NdotL = clamp(dot(n, l), 0.001, 1.0); float NdotV = abs(dot(n, v)) + 0.001; float NdotH = clamp(dot(n, h), 0.0, 1.0); float LdotH = clamp(dot(l, h), 0.0, 1.0); float VdotH = clamp(dot(v, h), 0.0, 1.0); PBRInfo pbrInputs; pbrInputs.NdotL = NdotL; pbrInputs.NdotV = NdotV; pbrInputs.NdotH = NdotH; pbrInputs.LdotH = LdotH; pbrInputs.VdotH = VdotH; pbrInputs.perceptualRoughness = perceptualRoughness; pbrInputs.metalness = metallic; pbrInputs.reflectance0 = specularEnvironmentR0; pbrInputs.reflectance90 = specularEnvironmentR90; pbrInputs.alphaRoughness = alphaRoughness; pbrInputs.diffuseColor = diffuseColor; pbrInputs.specularColor = specularColor; // Calculate the shading terms for the microfacet specular shading model float3 F = specularReflection(pbrInputs); float G = geometricOcclusion(pbrInputs); float D = microfacetDistribution(pbrInputs); // Calculation of analytical lighting contribution float3 diffuseContrib = (1.0 - F) * diffuse(pbrInputs); float3 specContrib = F * G * D / (4.0 * NdotL * NdotV); float3 color = NdotL * lightColour * (diffuseContrib + specContrib); // Calculate lighting contribution from image based lighting source (IBL) #ifdef USE_IBL color += getIBLContribution(pbrInputs, n, reflection); #endif // Apply optional PBR terms for additional (optional) shading #ifdef HAS_OCCLUSIONMAP float ao = SAMPLE_TEXTURE(occlusionTexture, input.texcoord).r; color = lerp(color, color * ao, occlusionStrength); #endif #ifdef HAS_EMISSIVEMAP float3 emissive = SRGBtoLINEAR(SAMPLE_TEXTURE(emissionTexture, input.texcoord)).rgb * emissiveFactor; color += emissive; #endif // This section uses lerp to override final color for reference app visualization // of various parameters in the lighting equation. color = lerp(color, F, scaleFGDSpec.x); color = lerp(color, float3(G, G, G), scaleFGDSpec.y); color = lerp(color, float3(D, D, D), scaleFGDSpec.z); color = lerp(color, specContrib, scaleFGDSpec.w); color = lerp(color, diffuseContrib, scaleDiffBaseMR.x); color = lerp(color, baseColor.rgb, scaleDiffBaseMR.y); color = lerp(color, float3(metallic, metallic, metallic), scaleDiffBaseMR.z); color = lerp(color, float3(perceptualRoughness, perceptualRoughness, perceptualRoughness), scaleDiffBaseMR.w); return float4(color, 1.0); } Technique PBR { Pass pass1 { VertexShader = compile vs_3_0 main_vs(); PixelShader = compile ps_3_0 main_ps(); } }