Fix Sheen BRDF

localDev/index.html

@@ -90,7 +90,7 @@
                     if (typeof createEngine !== "undefined") {
                         engine = createEngine();
                     } else {
-                        engine = new BABYLON.Engine(canvas, true, { stencil: true, disableWebGL2Support: false, preserveDrawingBuffer: true });
+                        engine = new BABYLON.Engine(canvas, true, {  premultipliedAlpha: false, stencil: true, disableWebGL2Support: false, preserveDrawingBuffer: true });
                     }
 
                     BABYLONDEVTOOLS.Loader.debugShortcut(engine);

src/Materials/PBR/pbrBRDFConfiguration.ts

@@ -16,16 +16,28 @@ export interface IMaterialBRDFDefines {
  */
 export class PBRBRDFConfiguration {
 
+    /**
+     * Default value used for the energy conservation.
+     * This should only be changed to adapt to the type of texture in scene.environmentBRDFTexture.
+     */
+    public static DEFAULT_USE_ENERGY_CONSERVATION = true;
+
+    /**
+     * Default value used for the Smith Visibility Height Correlated mode.
+     * This should only be changed to adapt to the type of texture in scene.environmentBRDFTexture.
+     */
+    public static DEFAULT_USE_SMITH_VISIBILITY_HEIGHT_CORRELATED = true;
+
     @serialize()
-    private _useEnergyConservation = true;
+    private _useEnergyConservation = PBRBRDFConfiguration.DEFAULT_USE_ENERGY_CONSERVATION;
     /**
      * Defines if the material uses energy conservation.
      */
     @expandToProperty("_markAllSubMeshesAsMiscDirty")
-    public useEnergyConservation = true;
+    public useEnergyConservation = PBRBRDFConfiguration.DEFAULT_USE_ENERGY_CONSERVATION;
 
     @serialize()
-    private _useSmithVisibilityHeightCorrelated = true;
+    private _useSmithVisibilityHeightCorrelated = PBRBRDFConfiguration.DEFAULT_USE_SMITH_VISIBILITY_HEIGHT_CORRELATED;
     /**
      * LEGACY Mode set to false
      * Defines if the material uses height smith correlated visibility term.
@@ -35,7 +47,7 @@ export class PBRBRDFConfiguration {
      * Not relying on height correlated will also disable energy conservation.
      */
     @expandToProperty("_markAllSubMeshesAsMiscDirty")
-    public useSmithVisibilityHeightCorrelated = true;
+    public useSmithVisibilityHeightCorrelated = PBRBRDFConfiguration.DEFAULT_USE_SMITH_VISIBILITY_HEIGHT_CORRELATED;
 
     /** @hidden */
     private _internalMarkAllSubMeshesAsMiscDirty: () => void;

src/Materials/PBR/pbrBaseMaterial.ts

@@ -96,6 +96,7 @@ class PBRMaterialDefines extends MaterialDefines
     public METALLNESSSTOREINMETALMAPBLUE = false;
     public AOSTOREINMETALMAPRED = false;
     public ENVIRONMENTBRDF = false;
+    public ENVIRONMENTBRDF_RGBD = false;
 
     public NORMAL = false;
     public TANGENT = false;
@@ -1448,8 +1449,11 @@ export abstract class PBRBaseMaterial extends PushMaterial {
 
                 if (this._environmentBRDFTexture && MaterialFlags.ReflectionTextureEnabled) {
                     defines.ENVIRONMENTBRDF = true;
+                    // Not actual true RGBD, only the B chanel is encoded as RGBD for sheen.
+                    defines.ENVIRONMENTBRDF_RGBD = this._environmentBRDFTexture.isRGBD;
                 } else {
                     defines.ENVIRONMENTBRDF = false;
+                    defines.ENVIRONMENTBRDF_RGBD = false;
                 }
 
                 if (this._shouldUseAlphaFromAlbedoTexture()) {
@@ -2123,7 +2127,7 @@ export abstract class PBRBaseMaterial extends PushMaterial {
                 this._reflectionTexture.dispose();
             }
 
-            if (this._environmentBRDFTexture && this.getScene()._environmentBRDFTexture !== this._environmentBRDFTexture) {
+            if (this._environmentBRDFTexture && this.getScene().environmentBRDFTexture !== this._environmentBRDFTexture) {
                 this._environmentBRDFTexture.dispose();
             }
 

src/Materials/Textures/internalTexture.ts

@@ -418,6 +418,7 @@ export class InternalTexture implements IInternalTextureTracker {
     /** @hidden */
     public _swapAndDie(target: InternalTexture): void {
         target._webGLTexture = this._webGLTexture;
+        target._isRGBD = this._isRGBD;
 
         if (this._framebuffer) {
             target._framebuffer = this._framebuffer;

src/Shaders/ShadersInclude/pbrBRDFFunctions.fx

@@ -9,23 +9,27 @@
 #ifdef MS_BRDF_ENERGY_CONSERVATION
     // http://www.jcgt.org/published/0008/01/03/
     // http://advances.realtimerendering.com/s2018/Siggraph%202018%20HDRP%20talk_with%20notes.pdf
-    vec3 getEnergyConservationFactor(const vec3 specularEnvironmentR0, vec2 environmentBrdf) {
+    vec3 getEnergyConservationFactor(const vec3 specularEnvironmentR0, const vec3 environmentBrdf) {
         return 1.0 + specularEnvironmentR0 * (1.0 / environmentBrdf.y - 1.0);
     }
 #endif
 
 #ifdef ENVIRONMENTBRDF
-    vec2 getBRDFLookup(float NdotV, float perceptualRoughness, sampler2D brdfSampler) {
+    vec3 getBRDFLookup(float NdotV, float perceptualRoughness, sampler2D brdfSampler) {
         // Indexed on cos(theta) and roughness
         vec2 UV = vec2(NdotV, perceptualRoughness);
         
         // We can find the scale and offset to apply to the specular value.
-        vec2 brdfLookup = texture2D(brdfSampler, UV).xy;
+        vec4 brdfLookup = texture2D(brdfSampler, UV);
 
-        return brdfLookup;
+        #ifdef ENVIRONMENTBRDF_RGBD
+            brdfLookup.rgb = fromRGBD(brdfLookup.rgba);
+        #endif
+
+        return brdfLookup.rgb;
     }
 
-    vec3 getReflectanceFromBRDFLookup(const vec3 specularEnvironmentR0, vec2 environmentBrdf) {
+    vec3 getReflectanceFromBRDFLookup(const vec3 specularEnvironmentR0, const vec3 environmentBrdf) {
         #ifdef BRDF_V_HEIGHT_CORRELATED
             vec3 reflectance = mix(environmentBrdf.xxx, environmentBrdf.yyy, specularEnvironmentR0);
         #else
@@ -46,36 +50,12 @@
 
 #if defined(SHEEN) && defined(REFLECTION)
     /**
-    * Special thanks to @romainguy for all the support :-)
-    * Analytical approximation of the pre-filtered DFG terms for the cloth shading
-    * model. This approximation is based on the Estevez & Kulla distribution term
-    * ("Charlie" sheen) and the Neubelt visibility term. See brdf.fs for more
-    * details.
-    */
-    vec2 getCharlieSheenAnalyticalBRDFLookup_RomainGuy(float NoV, float roughness) {
-        const vec3 c0 = vec3(0.95, 1250.0, 0.0095);
-        const vec4 c1 = vec4(0.04, 0.2, 0.3, 0.2);
-
-        float a = 1.0 - NoV;
-        float b = 1.0 - roughness;
-
-        float n = pow(c1.x + a, 64.0);
-        float e = b - c0.x;
-        float g = exp2(-(e * e) * c0.y);
-        float f = b + c1.y;
-        float a2 = a * a;
-        float a3 = a2 * a;
-        float c = n * g + c1.z * (a + c1.w) * roughness + f * f * a3 * a3 * a2;
-        float r = min(c, 18.0);
-
-        return vec2(r, r * c0.z);
-    }
-
-    vec3 getSheenReflectanceFromBRDFLookup(const vec3 reflectance0, float NdotV, float sheenAlphaG) {
-        vec2 environmentSheenBrdf = getCharlieSheenAnalyticalBRDFLookup_RomainGuy(NdotV, sheenAlphaG);
-        vec3 reflectance = reflectance0 * environmentSheenBrdf.x + environmentSheenBrdf.y;
-
-        return reflectance;
+     * The sheen BRDF not containing F can be easily stored in the blue channel of the BRDF texture.
+     * The blue channel contains DCharlie * VAshikhmin * NdotL as a lokkup table
+     */
+    vec3 getSheenReflectanceFromBRDFLookup(const vec3 reflectance0, const vec3 environmentBrdf) {
+        vec3 sheenEnvironmentReflectance = reflectance0 * environmentBrdf.b;
+        return sheenEnvironmentReflectance;
     }
 #endif
 

src/Shaders/ShadersInclude/pbrDirectLightingFunctions.fx

@@ -123,12 +123,13 @@ vec3 computeProjectionTextureDiffuseLighting(sampler2D projectionLightSampler, m
         float roughness = max(info.roughness, geometricRoughnessFactor);
         float alphaG = convertRoughnessToAverageSlope(roughness);
 
-        // No Fresnel with sheen
+        // No Fresnel Effect with sheen
         // vec3 fresnel = fresnelSchlickGGX(info.VdotH, reflectance0, reflectance90);
+        vec3 fresnel = reflectance0;
         float distribution = normalDistributionFunction_CharlieSheen(NdotH, alphaG);
         float visibility = visibility_Ashikhmin(info.NdotL, info.NdotV);
 
-        float sheenTerm = distribution * visibility;
+        vec3 sheenTerm = fresnel * distribution * visibility;
         return sheenTerm * info.attenuation * info.NdotL * lightColor;
     }
 #endif

src/Shaders/pbr.fragment.fx

@@ -516,9 +516,12 @@ void main(void) {
                 sheenColor.rgb *= toLinearSpace(sheenMapData.rgb);
             #endif
             float sheenRoughness = roughness;
+
+            // Sheen Lobe Layering.
+            sheenIntensity *= (1. - reflectance);
+
             // Remap F0 and sheen.
             sheenColor *= sheenIntensity;
-            specularEnvironmentR0 *= (1.0-sheenIntensity);
         #endif
 
         // Sheen Reflection
@@ -731,7 +734,7 @@ void main(void) {
     // _____________________________ IBL BRDF + Energy Cons _________________________________
     #if defined(ENVIRONMENTBRDF)
         // BRDF Lookup
-        vec2 environmentBrdf = getBRDFLookup(NdotV, roughness, environmentBrdfSampler);
+        vec3 environmentBrdf = getBRDFLookup(NdotV, roughness, environmentBrdfSampler);
 
         #ifdef MS_BRDF_ENERGY_CONSERVATION
             vec3 energyConservationFactor = getEnergyConservationFactor(specularEnvironmentR0, environmentBrdf);
@@ -796,7 +799,7 @@ void main(void) {
 
     // _____________________________ Sheen Environment Oclusion __________________________
     #if defined(SHEEN) && defined(REFLECTION)
-        vec3 sheenEnvironmentReflectance = getSheenReflectanceFromBRDFLookup(sheenColor, NdotV, sheenAlphaG);
+        vec3 sheenEnvironmentReflectance = getSheenReflectanceFromBRDFLookup(sheenColor, environmentBrdf);
 
         #ifdef RADIANCEOCCLUSION
             sheenEnvironmentReflectance *= seo;
@@ -815,7 +818,7 @@ void main(void) {
     #ifdef CLEARCOAT
         #if defined(ENVIRONMENTBRDF) && !defined(REFLECTIONMAP_SKYBOX)
             // BRDF Lookup
-            vec2 environmentClearCoatBrdf = getBRDFLookup(clearCoatNdotV, clearCoatRoughness, environmentBrdfSampler);
+            vec3 environmentClearCoatBrdf = getBRDFLookup(clearCoatNdotV, clearCoatRoughness, environmentBrdfSampler);
             vec3 clearCoatEnvironmentReflectance = getReflectanceFromBRDFLookup(vec3(vClearCoatRefractionParams.x), environmentClearCoatBrdf);
 
             #ifdef RADIANCEOCCLUSION
@@ -985,11 +988,11 @@ void main(void) {
         finalSheen = max(finalSheen, 0.0);
 
         vec3 finalSheenScaled = finalSheen * vLightingIntensity.x * vLightingIntensity.w;
-        #if defined(ENVIRONMENTBRDF) && defined(MS_BRDF_ENERGY_CONSERVATION)
+        // #if defined(ENVIRONMENTBRDF) && defined(MS_BRDF_ENERGY_CONSERVATION)
             // The sheen does not use the same BRDF so not energy conservation is possible
             // Should be less a problem as it is usually not metallic
             // finalSheenScaled *= energyConservationFactor;
-        #endif
+        // #endif
         
         #ifdef REFLECTION
             vec3 finalSheenRadiance = environmentSheenRadiance.rgb;

src/scene.ts

@@ -188,8 +188,15 @@ export class Scene extends AbstractScene implements IAnimatable {
      */
     public ambientColor = new Color3(0, 0, 0);
 
-    /** @hidden */
-    public _environmentBRDFTexture: BaseTexture;
+    /**
+     * This is use to store the default BRDF lookup for PBR materials in your scene.
+     * It should only be one of the following (if not the default embedded one):
+     * * For uncorrelated BRDF (pbr.brdf.useEnergyConservation = false and pbr.brdf.useSmithVisibilityHeightCorrelated = false) : https://assets.babylonjs.com/environments/uncorrelatedBRDF.dds
+     * * For correlated BRDF (pbr.brdf.useEnergyConservation = false and pbr.brdf.useSmithVisibilityHeightCorrelated = true) : https://assets.babylonjs.com/environments/correlatedBRDF.dds
+     * * For correlated multi scattering BRDF (pbr.brdf.useEnergyConservation = true and pbr.brdf.useSmithVisibilityHeightCorrelated = true) : https://assets.babylonjs.com/environments/correlatedMSBRDF.dds
+     * The material properties need to be setup according to the type of texture in use.
+     */
+    public environmentBRDFTexture: BaseTexture;
 
     /** @hidden */
     protected _environmentTexture: Nullable<BaseTexture>;

tests/unit/babylon/src/Loading/babylon.sceneLoader.tests.ts

@@ -121,7 +121,7 @@ describe('Babylon Scene Loader', function() {
                 expect(meshCount, "meshCount").to.equal(scene.meshes.length);
                 expect(materialCount, "materialCount").to.equal(scene.materials.length);
 
-                const filteredTextures = scene.textures.filter((texture) => texture !== scene._environmentBRDFTexture);
+                const filteredTextures = scene.textures.filter((texture) => texture !== scene.environmentBRDFTexture);
                 expect(textureCount, "textureCount").to.equal(filteredTextures.length);
             }));