Refactoring of TBN shader part of lit-shader (#7389)

Co-authored-by: Martin Valigursky <[email protected]>

src/scene/shader-lib/chunks-wgsl/chunks-wgsl.js

@@ -177,8 +177,6 @@ import sphericalPS from './common/frag/spherical.js';
 // import startNineSlicedTiledPS from './lit/frag/startNineSlicedTiled.js';
 // import tangentBinormalVS from './lit/vert/tangentBinormal.js';
 // import TBNPS from './lit/frag/TBN.js';
-// import TBNderivativePS from './lit/frag/TBNderivative.js';
-// import TBNObjectSpacePS from './lit/frag/TBNObjectSpace.js';
 // import thicknessPS from './standard/frag/thickness.js';
 import tonemappingPS from './common/frag/tonemapping/tonemapping.js';
 import tonemappingAcesPS from './common/frag/tonemapping/tonemappingAces.js';
@@ -388,8 +386,6 @@ const shaderChunksWGSL = {
     // startNineSlicedTiledPS,
     // tangentBinormalVS,
     // TBNPS,
-    // TBNderivativePS,
-    // TBNObjectSpacePS,
     // thicknessPS,
     tonemappingPS,
     tonemappingAcesPS,

src/scene/shader-lib/chunks/chunk-validation.js

@@ -65,8 +65,6 @@ const chunkVersions = {
     shadowEVSMPS: CHUNKAPI_1_62,
     spotPS: CHUNKAPI_1_62,
     TBNPS: CHUNKAPI_1_62,
-    TBNObjectSpacePS: CHUNKAPI_1_62,
-    TBNderivativePS: CHUNKAPI_1_62,
 
     endPS: CHUNKAPI_1_65,
     metalnessModulatePS: CHUNKAPI_1_65,
@@ -120,7 +118,9 @@ const removedChunks = {
     baseVS: CHUNKAPI_2_6,
     baseNineSlicedVS: CHUNKAPI_2_6,
     viewNormalVS: CHUNKAPI_2_6,
-    lightmapDirAddPS: CHUNKAPI_2_6
+    lightmapDirAddPS: CHUNKAPI_2_6,
+    TBNObjectSpacePS: CHUNKAPI_2_6,
+    TBNderivativePS: CHUNKAPI_2_6
 };
 
 // compare two "major.minor" semantic version strings and return true if a is a smaller version than b.

src/scene/shader-lib/chunks/chunks.js

@@ -177,8 +177,6 @@ import startNineSlicedPS from './lit/frag/startNineSliced.js';
 import startNineSlicedTiledPS from './lit/frag/startNineSlicedTiled.js';
 import tangentBinormalVS from './lit/vert/tangentBinormal.js';
 import TBNPS from './lit/frag/TBN.js';
-import TBNderivativePS from './lit/frag/TBNderivative.js';
-import TBNObjectSpacePS from './lit/frag/TBNObjectSpace.js';
 import thicknessPS from './standard/frag/thickness.js';
 import tonemappingPS from './common/frag/tonemapping/tonemapping.js';
 import tonemappingAcesPS from './common/frag/tonemapping/tonemappingAces.js';
@@ -388,8 +386,6 @@ const shaderChunks = {
     startNineSlicedTiledPS,
     tangentBinormalVS,
     TBNPS,
-    TBNderivativePS,
-    TBNObjectSpacePS,
     thicknessPS,
     tonemappingPS,
     tonemappingAcesPS,

src/scene/shader-lib/chunks/lit/frag/TBN.js

@@ -1,5 +1,72 @@
 export default /* glsl */`
+
+#ifdef LIT_TANGENTS
+    #define TBN_TANGENTS
+#else
+    #if defined(LIT_USE_NORMALS) || defined(LIT_USE_CLEARCOAT_NORMALS)
+        #define TBN_DERIVATIVES
+    #endif
+#endif
+
+#if defined(TBN_DERIVATIVES)
+    uniform float tbnBasis;
+#endif
+
 void getTBN(vec3 tangent, vec3 binormal, vec3 normal) {
-    dTBN = mat3(normalize(tangent), normalize(binormal), normalize(normal));
+
+    #ifdef TBN_TANGENTS // tangents / binormals based TBN
+
+        dTBN = mat3(normalize(tangent), normalize(binormal), normalize(normal));
+
+    #elif defined(TBN_DERIVATIVES) // derivatives based TBN
+
+        vec2 uv = {lightingUv};
+
+        // get edge vectors of the pixel triangle
+        vec3 dp1 = dFdx( vPositionW );
+        vec3 dp2 = dFdy( vPositionW );
+        vec2 duv1 = dFdx( uv );
+        vec2 duv2 = dFdy( uv );
+
+        // solve the linear system
+        vec3 dp2perp = cross( dp2, normal );
+        vec3 dp1perp = cross( normal, dp1 );
+        vec3 T = dp2perp * duv1.x + dp1perp * duv2.x;
+        vec3 B = dp2perp * duv1.y + dp1perp * duv2.y;
+
+        // construct a scale-invariant frame
+        float denom = max( dot(T,T), dot(B,B) );
+        float invmax = (denom == 0.0) ? 0.0 : tbnBasis / sqrt( denom );
+        dTBN = mat3(T * invmax, -B * invmax, normal );
+
+    #else // object space TBN
+
+        vec3 B = cross(normal, vObjectSpaceUpW);
+        vec3 T = cross(normal, B);
+
+        if (dot(B,B)==0.0) // deal with case when vObjectSpaceUpW normal are parallel
+        {
+            float major=max(max(normal.x, normal.y), normal.z);
+
+            if (normal.x == major)
+            {
+                B = cross(normal, vec3(0,1,0));
+                T = cross(normal, B);
+            }
+            else if (normal.y == major)
+            {
+                B = cross(normal, vec3(0,0,1));
+                T = cross(normal, B);
+            }
+            else if (normal.z == major)
+            {
+                B = cross(normal, vec3(1,0,0));
+                T = cross(normal, B);
+            }
+        }
+
+        dTBN = mat3(normalize(T), normalize(B), normalize(normal));
+
+    #endif
 }
 `;

src/scene/shader-lib/programs/lit-shader.js

@@ -505,6 +505,8 @@ class LitShader {
         const backend = new ChunkBuilder();
         const code = new ChunkBuilder();
 
+        const hasTBN = this.needsNormal && (options.useNormals || options.useClearCoatNormals || (options.enableGGXSpecular && !options.useHeights));
+
         if (options.useSpecular) {
             this.fDefineSet(true, 'LIT_SPECULAR');
             this.fDefineSet(this.reflections, 'LIT_REFLECTIONS');
@@ -522,6 +524,18 @@ class LitShader {
         this.fDefineSet(options.twoSidedLighting, 'LIT_TWO_SIDED_LIGHTING');
         this.fDefineSet(options.lightMapEnabled, 'LIT_LIGHTMAP');
         this.fDefineSet(options.dirLightMapEnabled, 'LIT_DIR_LIGHTMAP');
+        this.fDefineSet(hasTBN, 'LIT_TBN');
+        this.fDefineSet(options.hasTangents, 'LIT_TANGENTS');
+        this.fDefineSet(options.useNormals, 'LIT_USE_NORMALS');
+        this.fDefineSet(options.useClearCoatNormals, 'LIT_USE_CLEARCOAT_NORMALS');
+
+        // injection defines
+        this.fDefineSet(true, '{lightingUv}', this.lightingUv ?? ''); // example: vUV0_1
+
+        // globals
+        decl.append(`
+            mat3 dTBN;
+        `);
 
         // FRAGMENT SHADER INPUTS: UNIFORMS
 
@@ -555,33 +569,23 @@ class LitShader {
             #include "lightingPS"
         `);
 
-        // TBN
-        const hasTBN = this.needsNormal && (options.useNormals || options.useClearCoatNormals || (options.enableGGXSpecular && !options.useHeights));
+        func.append(`
 
-        if (hasTBN) {
-            if (options.hasTangents) {
-                func.append(chunks.TBNPS);
-            } else {
-                if (options.useNormals || options.useClearCoatNormals) {
-                    func.append(chunks.TBNderivativePS.replace(/\$UV/g, this.lightingUv));
-                } else {
-                    func.append(chunks.TBNObjectSpacePS);
-                }
-            }
+            // TBN
+            #ifdef LIT_TBN
+                #include "TBNPS"
 
-            func.append(`
                 #ifdef LIT_TWO_SIDED_LIGHTING
                     #include "twoSidedLightingPS"
                 #endif
-            `);
-        }
+            #endif
 
-        func.append(`
             #include "sphericalPS"
             #include "decodePS"
             #include "gammaPS"
             #include "tonemappingPS"
             #include "fogPS"
+
         `);
 
         // frontend
@@ -800,16 +804,17 @@ class LitShader {
                 code.append('    dBinormalW = vBinormalW;');
             }
 
-            code.append('    getViewDir();');
-            if (hasTBN) {
-                code.append(`
+            code.append(`
+                getViewDir();
+
+                #ifdef LIT_TBN
                     getTBN(dTangentW, dBinormalW, dVertexNormalW);
 
                     #ifdef LIT_TWO_SIDED_LIGHTING
                         handleTwoSidedLighting();
                     #endif
-                `);
-            }
+                #endif
+            `);
         }
 
         // invoke frontend functions
@@ -1354,7 +1359,6 @@ class LitShader {
         const mergedCode = decl.code + func.code + code.code;
 
         // Light inputs
-        if (mergedCode.includes('dTBN')) structCode += 'mat3 dTBN;\n';
         if (mergedCode.includes('dVertexNormalW')) structCode += 'vec3 dVertexNormalW;\n';
         if (mergedCode.includes('dTangentW')) structCode += 'vec3 dTangentW;\n';
         if (mergedCode.includes('dBinormalW')) structCode += 'vec3 dBinormalW;\n';