From 8e23c37668acafd072cbde6a8310be9680dda6e0 Mon Sep 17 00:00:00 2001
From: scrawl <scrawl@baseoftrash.de>
Date: Thu, 16 Jun 2016 18:07:10 +0200
Subject: [PATCH] Flip the parallax offset Y component based on tangent parity
 (Bug #3440)

---
 files/shaders/objects_fragment.glsl | 6 +++---
 files/shaders/objects_vertex.glsl   | 4 ++--
 files/shaders/parallax.glsl         | 4 ++--
 files/shaders/terrain_fragment.glsl | 2 +-
 4 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/files/shaders/objects_fragment.glsl b/files/shaders/objects_fragment.glsl
index 8f21e7247..ac8c2d591 100644
--- a/files/shaders/objects_fragment.glsl
+++ b/files/shaders/objects_fragment.glsl
@@ -28,7 +28,7 @@ varying vec2 emissiveMapUV;
 #if @normalMap
 uniform sampler2D normalMap;
 varying vec2 normalMapUV;
-varying vec3 passTangent;
+varying vec4 passTangent;
 #endif
 
 #if @envMap
@@ -69,7 +69,7 @@ void main()
     vec4 normalTex = texture2D(normalMap, normalMapUV);
 
     vec3 normalizedNormal = normalize(passNormal);
-    vec3 normalizedTangent = normalize(passTangent);
+    vec3 normalizedTangent = normalize(passTangent.xyz);
     vec3 binormal = cross(normalizedTangent, normalizedNormal);
     mat3 tbnTranspose = mat3(normalizedTangent, binormal, normalizedNormal);
 
@@ -82,7 +82,7 @@ void main()
     vec3 cameraPos = (gl_ModelViewMatrixInverse * vec4(0,0,0,1)).xyz;
     vec3 objectPos = (gl_ModelViewMatrixInverse * vec4(passViewPos, 1)).xyz;
     vec3 eyeDir = normalize(cameraPos - objectPos);
-    vec2 offset = getParallaxOffset(eyeDir, tbnTranspose, normalTex.a);
+    vec2 offset = getParallaxOffset(eyeDir, tbnTranspose, normalTex.a, (passTangent.w > 0) ? -1.f : 1.f);
     adjustedDiffuseUV += offset; // only offset diffuse for now, other textures are more likely to be using a completely different UV set
 
     // TODO: check not working as the same UV buffer is being bound to different targets
diff --git a/files/shaders/objects_vertex.glsl b/files/shaders/objects_vertex.glsl
index 9aabbe696..e140cd6ad 100644
--- a/files/shaders/objects_vertex.glsl
+++ b/files/shaders/objects_vertex.glsl
@@ -22,7 +22,7 @@ varying vec2 emissiveMapUV;
 
 #if @normalMap
 varying vec2 normalMapUV;
-varying vec3 passTangent;
+varying vec4 passTangent;
 #endif
 
 #if @envMap
@@ -85,7 +85,7 @@ void main(void)
 
 #if @normalMap
     normalMapUV = (gl_TextureMatrix[@normalMapUV] * gl_MultiTexCoord@normalMapUV).xy;
-    passTangent = gl_MultiTexCoord7.xyz;
+    passTangent = gl_MultiTexCoord7.xyzw;
 #endif
 
 #if @specularMap
diff --git a/files/shaders/parallax.glsl b/files/shaders/parallax.glsl
index 097a59ed1..433dbcd3e 100644
--- a/files/shaders/parallax.glsl
+++ b/files/shaders/parallax.glsl
@@ -1,8 +1,8 @@
 #define PARALLAX_SCALE 0.04
 #define PARALLAX_BIAS -0.02
 
-vec2 getParallaxOffset(vec3 eyeDir, mat3 tbnTranspose, float height)
+vec2 getParallaxOffset(vec3 eyeDir, mat3 tbnTranspose, float height, float flipY)
 {
     vec3 TSeyeDir = normalize(eyeDir * tbnTranspose);
-    return TSeyeDir.xy * ( height * PARALLAX_SCALE + PARALLAX_BIAS );
+    return vec2(TSeyeDir.x, TSeyeDir.y * flipY) * ( height * PARALLAX_SCALE + PARALLAX_BIAS );
 }
diff --git a/files/shaders/terrain_fragment.glsl b/files/shaders/terrain_fragment.glsl
index d05a94687..0995a2d44 100644
--- a/files/shaders/terrain_fragment.glsl
+++ b/files/shaders/terrain_fragment.glsl
@@ -53,7 +53,7 @@ void main()
     vec3 cameraPos = (gl_ModelViewMatrixInverse * vec4(0,0,0,1)).xyz;
     vec3 objectPos = (gl_ModelViewMatrixInverse * vec4(passViewPos, 1)).xyz;
     vec3 eyeDir = normalize(cameraPos - objectPos);
-    adjustedUV += getParallaxOffset(eyeDir, tbnTranspose, normalTex.a);
+    adjustedUV += getParallaxOffset(eyeDir, tbnTranspose, normalTex.a, 1.f);
 
     // update normal using new coordinates
     normalTex = texture2D(normalMap, adjustedUV);