Merge pull request #13916 from WestLangley/dev-normal_bump

Handle normal/bump maps when material is back/double-sided

src/renderers/WebGLRenderer.js

@@ -8,7 +8,8 @@ import {
 	TriangleStripDrawMode,
 	TrianglesDrawMode,
 	NoColors,
-	LinearToneMapping
+	LinearToneMapping,
+	BackSide
 } from '../constants.js';
 import { _Math } from '../math/Math.js';
 import { DataTexture } from '../textures/DataTexture.js';
@@ -2140,6 +2141,7 @@ function WebGLRenderer( parameters ) {
 
 			uniforms.bumpMap.value = material.bumpMap;
 			uniforms.bumpScale.value = material.bumpScale;
+			if ( material.side === BackSide ) uniforms.bumpScale.value *= - 1;
 
 		}
 
@@ -2147,6 +2149,7 @@ function WebGLRenderer( parameters ) {
 
 			uniforms.normalMap.value = material.normalMap;
 			uniforms.normalScale.value.copy( material.normalScale );
+			if ( material.side === BackSide ) uniforms.normalScale.value.negate();
 
 		}
 
@@ -2199,6 +2202,7 @@ function WebGLRenderer( parameters ) {
 
 			uniforms.bumpMap.value = material.bumpMap;
 			uniforms.bumpScale.value = material.bumpScale;
+			if ( material.side === BackSide ) uniforms.bumpScale.value *= - 1;
 
 		}
 
@@ -2206,6 +2210,7 @@ function WebGLRenderer( parameters ) {
 
 			uniforms.normalMap.value = material.normalMap;
 			uniforms.normalScale.value.copy( material.normalScale );
+			if ( material.side === BackSide ) uniforms.normalScale.value.negate();
 
 		}
 
@@ -2269,6 +2274,7 @@ function WebGLRenderer( parameters ) {
 
 			uniforms.bumpMap.value = material.bumpMap;
 			uniforms.bumpScale.value = material.bumpScale;
+			if ( material.side === BackSide ) uniforms.bumpScale.value *= - 1;
 
 		}
 
@@ -2276,6 +2282,7 @@ function WebGLRenderer( parameters ) {
 
 			uniforms.normalMap.value = material.normalMap;
 			uniforms.normalScale.value.copy( material.normalScale );
+			if ( material.side === BackSide ) uniforms.normalScale.value.negate();
 
 		}
 

src/renderers/shaders/ShaderChunk/bumpmap_pars_fragment.glsl

@@ -34,6 +34,8 @@
 
 		float fDet = dot( vSigmaX, R1 );
 
+		fDet *= ( float( gl_FrontFacing ) * 2.0 - 1.0 );
+
 		vec3 vGrad = sign( fDet ) * ( dHdxy.x * R1 + dHdxy.y * R2 );
 		return normalize( abs( fDet ) * surf_norm - vGrad );
 

src/renderers/shaders/ShaderChunk/normalmap_pars_fragment.glsl

@@ -16,15 +16,17 @@
 		vec2 st1 = dFdy( vUv.st );
 
 		float scale = sign( st1.t * st0.s - st0.t * st1.s ); // we do not care about the magnitude
-		scale *= float( gl_FrontFacing ) * 2.0 - 1.0;
 
 		vec3 S = normalize( ( q0 * st1.t - q1 * st0.t ) * scale );
 		vec3 T = normalize( ( - q0 * st1.s + q1 * st0.s ) * scale );
 		vec3 N = normalize( surf_norm );
+		mat3 tsn = mat3( S, T, N );
 
 		vec3 mapN = texture2D( normalMap, vUv ).xyz * 2.0 - 1.0;
-		mapN.xy = normalScale * mapN.xy;
-		mat3 tsn = mat3( S, T, N );
+
+		mapN.xy *= normalScale;
+		mapN.xy *= ( float( gl_FrontFacing ) * 2.0 - 1.0 );
+
 		return normalize( tsn * mapN );
 
 	}