From 8ea7db4016bc56fa4683f4d82cf7999d2ee9ecd9 Mon Sep 17 00:00:00 2001
From: chubei-oppen <chubei@oppentech.com>
Date: Fri, 29 Apr 2022 15:39:22 +0800
Subject: [PATCH] Add a r115 compatible version `perturbNormal2Arb`

---
 src/materials/MeshMatcapMaterial.js            |  8 +++++++-
 src/materials/MeshStandardMaterial.js          |  1 +
 .../normalmap_pars_fragment.glsl.js            | 18 ++++++++++++++++++
 3 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/src/materials/MeshMatcapMaterial.js b/src/materials/MeshMatcapMaterial.js
index ea0992883b0248..9f11863f0b3c25 100644
--- a/src/materials/MeshMatcapMaterial.js
+++ b/src/materials/MeshMatcapMaterial.js
@@ -37,6 +37,12 @@ class MeshMatcapMaterial extends Material {
 
 		this.defines = { 'MATCAP': '' };
 
+		if ( Material.r115Compatible === true ) {
+
+			this.defines[ 'PERTURB_NORMAL_R115_COMPATABILITY' ] = '';
+
+		}
+
 		this.type = 'MeshMatcapMaterial';
 
 		this.color = new Color( 0xffffff ); // diffuse
@@ -69,7 +75,7 @@ class MeshMatcapMaterial extends Material {
 
 		super.copy( source );
 
-		this.defines = { 'MATCAP': '' };
+		this.defines = source.defines;
 
 		this.color.copy( source.color );
 
diff --git a/src/materials/MeshStandardMaterial.js b/src/materials/MeshStandardMaterial.js
index bfd45ca92bd109..819abd6006c502 100644
--- a/src/materials/MeshStandardMaterial.js
+++ b/src/materials/MeshStandardMaterial.js
@@ -65,6 +65,7 @@ class MeshStandardMaterial extends Material {
 
 			this.defines[ 'MULTISCATTERRING_R115_COMPATABILITY' ] = '';
 			this.defines[ 'ALPHA_R115_COMPATABILITY' ] = '';
+			this.defines[ 'PERTURB_NORMAL_R115_COMPATABILITY' ] = '';
 
 		}
 
diff --git a/src/renderers/shaders/ShaderChunk/normalmap_pars_fragment.glsl.js b/src/renderers/shaders/ShaderChunk/normalmap_pars_fragment.glsl.js
index 006bdb7abee86c..8d427965dd5565 100644
--- a/src/renderers/shaders/ShaderChunk/normalmap_pars_fragment.glsl.js
+++ b/src/renderers/shaders/ShaderChunk/normalmap_pars_fragment.glsl.js
@@ -32,6 +32,22 @@ export default /* glsl */`
 		vec2 st0 = dFdx( vUv.st );
 		vec2 st1 = dFdy( vUv.st );
 
+	#ifdef PERTURB_NORMAL_R115_COMPATABILITY
+
+		float scale = sign( st1.t * st0.s - st0.t * st1.s ); // we do not care about the magnitude
+
+		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 );
+
+		mapN.xy *= ( faceDirection * 2.0 - 1.0 );
+
+		return normalize( tsn * mapN );
+
+	#else
+
 		vec3 N = surf_norm; // normalized
 
 		vec3 q1perp = cross( q1, N );
@@ -45,6 +61,8 @@ export default /* glsl */`
 
 		return normalize( T * ( mapN.x * scale ) + B * ( mapN.y * scale ) + N * mapN.z );
 
+	#endif
+
 	}
 
 #endif