shaderlab pbr support refraction (#2470)

* feat: pbr support refraction

packages/core/src/material/PBRMaterial.ts

@@ -32,7 +32,6 @@ export class PBRMaterial extends PBRBaseMaterial {
 
   private static _transmissionMacro: ShaderMacro = ShaderMacro.getByName("MATERIAL_ENABLE_TRANSMISSION");
   private static _thicknessMacro: ShaderMacro = ShaderMacro.getByName("MATERIAL_HAS_THICKNESS");
-  private static _absorptionMacro: ShaderMacro = ShaderMacro.getByName("MATERIAL_HAS_ABSORPTION");
   private static _thicknessTextureMacro: ShaderMacro = ShaderMacro.getByName("MATERIAL_HAS_THICKNESS_TEXTURE");
   private static _transmissionTextureMacro: ShaderMacro = ShaderMacro.getByName("MATERIAL_HAS_TRANSMISSION_TEXTURE");
   private static _transmissionProp = ShaderProperty.getByName("material_Transmission");
@@ -46,7 +45,6 @@ export class PBRMaterial extends PBRBaseMaterial {
   private _anisotropyRotation: number = 0;
   private _iridescenceRange = new Vector2(100, 400);
   private _sheenEnabled = false;
-  private _absorptionEnabled = true;
 
   /**
    * Index Of Refraction.
@@ -317,7 +315,7 @@ export class PBRMaterial extends PBRBaseMaterial {
   set refractionMode(value: RefractionMode) {
     if (value !== this._refractionMode) {
       this._refractionMode = value;
-      this._setRefractionMode(value);
+      this.shaderData.enableMacro("REFRACTION_MODE", value.toString());
     }
   }
 
@@ -468,20 +466,17 @@ export class PBRMaterial extends PBRBaseMaterial {
     shaderData.setVector4(PBRMaterial._iridescenceInfoProp, new Vector4(0, 1.3, 100, 400));
     const sheenColor = new Color(0, 0, 0);
     shaderData.setColor(PBRMaterial._sheenColorProp, sheenColor);
-    this.refractionMode = RefractionMode.Plane;
+    this.refractionMode = RefractionMode.Planar;
     shaderData.setFloat(PBRMaterial._transmissionProp, 0);
     shaderData.setFloat(PBRMaterial._thicknessProp, 0);
     shaderData.setFloat(PBRMaterial._attenuationDistanceProp, Infinity);
     const attenuationColor = new Color(1, 1, 1);
     shaderData.setColor(PBRMaterial._attenuationColorProp, attenuationColor);
-    shaderData.enableMacro(PBRMaterial._absorptionMacro);
 
     // @ts-ignore
     this._iridescenceRange._onValueChanged = this._onIridescenceRangeChanged.bind(this);
     // @ts-ignore
     sheenColor._onValueChanged = this._onSheenColorChanged.bind(this);
-    // @ts-ignore
-    attenuationColor._onValueChanged = this._attenuationColorChanged.bind(this);
   }
 
   /**
@@ -511,31 +506,4 @@ export class PBRMaterial extends PBRBaseMaterial {
       }
     }
   }
-
-  private _attenuationColorChanged(): void {
-    const attenuationColor = this.attenuationColor;
-    const enableAbsorption = attenuationColor.r + attenuationColor.g + attenuationColor.b > 0;
-    if (enableAbsorption !== this._absorptionEnabled) {
-      this._absorptionEnabled = enableAbsorption;
-      if (enableAbsorption) {
-        this.shaderData.enableMacro(PBRMaterial._absorptionMacro);
-      } else {
-        this.shaderData.disableMacro(PBRMaterial._absorptionMacro);
-      }
-    }
-  }
-
-  private _setRefractionMode(refractionMode: RefractionMode): void {
-    switch (refractionMode) {
-      case RefractionMode.Sphere:
-        this.shaderData.enableMacro("REFRACTION_MODE", "SPHERE");
-        break;
-      case RefractionMode.Plane:
-        this.shaderData.enableMacro("REFRACTION_MODE", "PLANE");
-        break;
-      case RefractionMode.Thin:
-        this.shaderData.enableMacro("REFRACTION_MODE", "THIN");
-        break;
-    }
-  }
 }

packages/core/src/material/enums/Refraction.ts

@@ -2,10 +2,8 @@
  * Refraction mode.
  */
 export enum RefractionMode {
-  /** Refraction shape is sphere. */
-  Sphere,
-  /** Refraction shape is plane. */
-  Plane,
-  /** Refraction shape is thin. */
-  Thin
+  /** Use the sphere refraction model when light passes through the surface. */
+  Sphere = 0,
+  /** Use the planar refraction model when light passes through the surface. */
+  Planar = 1
 }

packages/shader-shaderlab/src/shaders/Common.glsl

@@ -6,7 +6,7 @@
 #define EPSILON 1e-6
 #define LOG2 1.442695
 #define HALF_MIN 6.103515625e-5  // 2^-14, the same value for 10, 11 and 16-bit: https://www.khronos.org/opengl/wiki/Small_Float_Formats
-// #define HALF_EPS 4.8828125e-4    // 2^-11, machine epsilon: 1 + EPS = 1 (half of the ULP for 1.0f)
+#define HALF_EPS 4.8828125e-4    // 2^-11, machine epsilon: 1 + EPS = 1 (half of the ULP for 1.0f)
 
 #define saturate( a ) clamp( a, 0.0, 1.0 )
 
@@ -99,10 +99,10 @@ float remapDepthBufferLinear01(float z){
 	#define INVERSE_MAT(mat) inverseMat(mat)
 #endif
 
-// vec3 safeNormalize(vec3 inVec)
-// {
-//     float dp3 = max(float(HALF_MIN), dot(inVec, inVec));
-//     return inVec * inversesqrt(dp3);
-// }
+vec3 safeNormalize(vec3 inVec)
+{
+    float dp3 = max(float(HALF_MIN), dot(inVec, inVec));
+    return inVec * inversesqrt(dp3);
+}
 
 #endif

packages/shader-shaderlab/src/shaders/PBR.gs

@@ -58,6 +58,10 @@ Shader "PBR.gs" {
       Header("Transmission"){
         material_Transmission("Transmission", Range(0, 1, 0.01)) = 0;
         material_TransmissionTexture("TransmissionTexture", Texture2D);
+        material_AttenuationColor("AttenuationColor", Color ) = (1, 1, 1, 1);
+        material_AttenuationDistance("AttenuationDistance", Range(0, 1, 0.01)) = 0;
+        material_Thickness("Thickness", Range(0, 5, 0.01)) = 0;
+        material_ThicknessTexture("ThicknessTexture", Texture2D);
       }
 
       Header("Common") {

packages/shader-shaderlab/src/shaders/shadingPBR/BTDF.glsl

@@ -5,28 +5,35 @@
 
 #ifdef MATERIAL_ENABLE_TRANSMISSION 
     sampler2D camera_OpaqueTexture;
-    vec3 evaluateRefraction(SurfaceData surfaceData, BRDFData brdfData) {
+    vec3 evaluateTransmission(SurfaceData surfaceData, BRDFData brdfData) {
         RefractionModelResult ray;
-        #ifdef REFRACTION_MODE
-            refractionModelBox(-surfaceData.viewDir, surfaceData.position, surfaceData.normal, surfaceData.IOR, 0.005, ray);
+        #if REFRACTION_MODE == 0  
+            // RefractionMode.Sphere
+            refractionModelSphere(-surfaceData.viewDir, surfaceData.position, surfaceData.normal, surfaceData.IOR, surfaceData.thickness, ray);
+        #elif REFRACTION_MODE == 1
+            // RefractionMode.Planar
+            refractionModelPlanar(-surfaceData.viewDir, surfaceData.position, surfaceData.normal, surfaceData.IOR, surfaceData.thickness, ray);
         #endif
-        //TODO: support cubemap refraction.
+
         vec3 refractedRayExit = ray.positionExit;
 
         // We calculate the screen space position of the refracted point
         vec4 samplingPositionNDC = camera_ProjMat * camera_ViewMat * vec4( refractedRayExit, 1.0 );
         vec2 refractionCoords = (samplingPositionNDC.xy / samplingPositionNDC.w) * 0.5 + 0.5;
 
         // Sample the opaque texture to get the transmitted light
-		vec4 getTransmission = texture2D(camera_OpaqueTexture, refractionCoords);
-        vec3 refractionTransmitted = getTransmission.rgb;
+        vec3 refractionTransmitted = texture2D(camera_OpaqueTexture, refractionCoords).rgb;
         refractionTransmitted *= brdfData.diffuseColor;
 
         // Use specularFGD as an approximation of the fresnel effect
         // https://blog.selfshadow.com/publications/s2017-shading-course/imageworks/s2017_pbs_imageworks_slides_v2.pdf
-        vec3 specularDFG =  brdfData.envSpecularDFG;
+        refractionTransmitted *= (1.0 - brdfData.envSpecularDFG);
 
-        refractionTransmitted *= (1.0 - specularDFG);
+       #ifdef MATERIAL_HAS_THICKNESS
+            // Absorption coefficient from Disney: http://blog.selfshadow.com/publications/s2015-shading-course/burley/s2015_pbs_disney_bsdf_notes.pdf
+            vec3 transmittance = min(vec3(1.0), exp(-surfaceData.absorptionCoefficient * ray.transmissionLength));
+            refractionTransmitted *= transmittance;
+       #endif
 
     return refractionTransmitted;
     }

packages/shader-shaderlab/src/shaders/shadingPBR/ForwardPassPBR.glsl

@@ -95,7 +95,7 @@ void PBRFragment(Varyings varyings) {
   evaluateIBL(varyings, surfaceData, brdfData, totalDiffuseColor, totalSpecularColor);
 
   #ifdef MATERIAL_ENABLE_TRANSMISSION 
-      vec3 refractionTransmitted = evaluateRefraction(surfaceData, brdfData);
+      vec3 refractionTransmitted = evaluateTransmission(surfaceData, brdfData);
       totalDiffuseColor = mix(totalDiffuseColor, refractionTransmitted, surfaceData.transmission);
   #endif
 

packages/shader-shaderlab/src/shaders/shadingPBR/FragmentPBR.glsl

@@ -62,11 +62,20 @@ float material_OcclusionTextureCoord;
     #endif
 #endif
 
-#ifdef MATERIAL_ENABLE_TRANSMISSION    
-        float material_Transmission;
-        #ifdef MATERIAL_HAS_TRANSMISSION_TEXTURE
-            sampler2D material_TransmissionTexture;
+#ifdef MATERIAL_ENABLE_TRANSMISSION
+    float material_Transmission;
+    #ifdef MATERIAL_HAS_TRANSMISSION_TEXTURE
+        sampler2D material_TransmissionTexture;
+    #endif
+
+    #ifdef MATERIAL_HAS_THICKNESS
+        vec3 material_AttenuationColor;
+        float material_AttenuationDistance;
+        float material_Thickness;
+        #ifdef MATERIAL_HAS_THICKNESS_TEXTURE
+            sampler2D material_ThicknessTexture;
         #endif
+    #endif
 #endif
 
 // Texture
@@ -302,10 +311,18 @@ SurfaceData getSurfaceData(Varyings v, vec2 aoUV, bool isFrontFacing){
     #endif
 
     #ifdef MATERIAL_ENABLE_TRANSMISSION 
-            surfaceData.transmission = material_Transmission;
-            #ifdef MATERIAL_HAS_TRANSMISSION_TEXTURE
-                surfaceData.transmission *= texture2D(material_TransmissionTexture, uv).r;
-            #endif
+        surfaceData.transmission = material_Transmission;
+        #ifdef MATERIAL_HAS_TRANSMISSION_TEXTURE
+            surfaceData.transmission *= texture2D(material_TransmissionTexture, uv).r;
+        #endif
+
+        #ifdef MATERIAL_HAS_THICKNESS
+                surfaceData.absorptionCoefficient = -log(material_AttenuationColor + HALF_EPS) / max(HALF_EPS, material_AttenuationDistance);
+                surfaceData.thickness = max(material_Thickness, 0.0001);
+                #ifdef MATERIAL_HAS_THICKNESS_TEXTURE
+                    surfaceData.thickness *= texture2D( material_ThicknessTexture, uv).g;
+                #endif
+        #endif    
     #endif
 
     // AO

packages/shader-shaderlab/src/shaders/shadingPBR/Refraction.glsl

@@ -9,7 +9,28 @@ struct RefractionModelResult{
     // vec3 directionExit;     // out ray direction
 };
 
-void refractionModelBox(vec3 V, vec3 positionWS, vec3 normalWS, float ior, float thickness, out RefractionModelResult ray){
+//https://docs.unity3d.com/Packages/[email protected]/manual/refraction-models.html
+ void refractionModelSphere(vec3 V, vec3 positionWS, vec3 normalWS, float ior, float thickness, out RefractionModelResult ray){
+    // Refracted ray
+    vec3 R1 = refract(V, normalWS, 1.0 / ior);
+    // Center of the tangent sphere
+    // vec3 C = positionWS - normalWS * thickness * 0.5;
+
+    // Second refraction (tangent sphere out)
+    float dist = dot(-normalWS, R1) * thickness;
+    // Out hit point in the tangent sphere
+    vec3 P1 = positionWS + R1 * dist;
+    // Out normal
+    // vec3 N1 = safeNormalize(C - P1);
+    // Out refracted ray
+    // vec3 R2 = refract(R1, N1, ior);
+
+    ray.transmissionLength = dist;
+    ray.positionExit = P1;
+    // ray.directionExit = R2; 
+}
+
+void refractionModelPlanar(vec3 V, vec3 positionWS, vec3 normalWS, float ior, float thickness, out RefractionModelResult ray){
     // Refracted ray
     vec3 R = refract(V, normalWS, 1.0 / ior);
     // Optical depth within the thin plane