diff --git a/shaders/bumpdiffuse.vp b/shaders/bumpdiffuse.vp
index 0892e7cc5..2f26bb6be 100644
--- a/shaders/bumpdiffuse.vp
+++ b/shaders/bumpdiffuse.vp
@@ -34,7 +34,7 @@ MAD   R3, R1.yzxw, R2.zxyw, -R3;
 
 # Transform the light direction from object space into surface space
 DP3   R0.x, R2, c[16];
-DP3   R0.y, R3, c[16];
+DP3   R0.y, -R3, c[16];
 DP3   R0.z, R1, c[16];
 # Compress the light direction to fit in the primary color and output it
 MOV   R5, c[40];
diff --git a/shaders/bumpdiffuse_arb.vp b/shaders/bumpdiffuse_arb.vp
index b49f04178..b94827073 100644
--- a/shaders/bumpdiffuse_arb.vp
+++ b/shaders/bumpdiffuse_arb.vp
@@ -37,7 +37,7 @@ MAD   binormal, iNormal.yzxw, t.zxyw, -binormal;
 
 # Transform the light direction from object space into surface space
 DP3   light_surf.x, iTangent, lightDir;
-DP3   light_surf.y, binormal, lightDir;
+DP3   light_surf.y, -binormal, lightDir;
 DP3   light_surf.z, iNormal, lightDir;
 
 # Compress the light direction to fit in the primary color and output it
diff --git a/shaders/bumphaze.vp b/shaders/bumphaze.vp
index e2b155314..6214dbd3b 100644
--- a/shaders/bumphaze.vp
+++ b/shaders/bumphaze.vp
@@ -52,7 +52,7 @@ MAD   R3, R1.yzxw, R2.zxyw, -R3;
 
 # Transform the light direction from object space into surface space
 DP3   R0.x, R2, c[16];
-DP3   R0.y, R3, c[16];
+DP3   R0.y, -R3, c[16];
 DP3   R0.z, R1, c[16];
 # Compress the light direction to fit in the primary color and output it
 MOV   R5, c[40];
diff --git a/shaders/bumphaze_arb.vp b/shaders/bumphaze_arb.vp
index b6774c137..30457ef03 100644
--- a/shaders/bumphaze_arb.vp
+++ b/shaders/bumphaze_arb.vp
@@ -65,7 +65,7 @@ MAD   binormal, iNormal.yzxw, t.zxyw, -binormal;
 
 # Transform the light direction from object space into surface space
 DP3   light_surf.x, iTangent, lightDir;
-DP3   light_surf.y, binormal, lightDir;
+DP3   light_surf.y, -binormal, lightDir;
 DP3   light_surf.z, iNormal, lightDir;
 
 # Compress the light direction to fit in the primary color and output it
diff --git a/src/celengine/lodspheremesh.cpp b/src/celengine/lodspheremesh.cpp
index 3e0ecc208..43bbe3d6a 100644
--- a/src/celengine/lodspheremesh.cpp
+++ b/src/celengine/lodspheremesh.cpp
@@ -574,7 +574,7 @@ void LODSphereMesh::renderSection(int phi0, int theta0,
                 // Compute the tangent--required for bump mapping
                 tangents[n3]      = stheta;
                 tangents[n3 + 1]  = 0.0f;
-                tangents[n3 + 2]  = ctheta;
+                tangents[n3 + 2]  = -ctheta;
                 
                 n2 += 2;
                 n3 += 3;
diff --git a/src/celengine/render.cpp b/src/celengine/render.cpp
index 02a904b30..3cbb47832 100644
--- a/src/celengine/render.cpp
+++ b/src/celengine/render.cpp
@@ -1572,6 +1572,7 @@ static void renderBumpMappedMesh(const GLContext& context,
     // Set up the texture transformation--the light direction and the
     // viewer orientation both need to be considered.
     glMatrixMode(GL_TEXTURE);
+    glScalef(-1.0f, 1.0f, 1.0f);
     glRotate(lightOrientation * ~orientation);
     glMatrixMode(GL_MODELVIEW);
     glx::glActiveTextureARB(GL_TEXTURE0_ARB);
diff --git a/src/celengine/texture.cpp b/src/celengine/texture.cpp
index 5f411aad1..f7294a1ed 100644
--- a/src/celengine/texture.cpp
+++ b/src/celengine/texture.cpp
@@ -741,14 +741,14 @@ void Texture::normalMap(float scale, bool wrap)
             int h01 = (int) pixels[(i1 * width + j0) * components];
             
             float dx = (float) (h10 - h00) * (1.0f / 255.0f) * scale;
-            float dy = (float) (h00 - h01) * (1.0f / 255.0f) * scale;
+            float dy = (float) (h01 - h00) * (1.0f / 255.0f) * scale;
 
             float mag = (float) sqrt(dx * dx + dy * dy + 1.0f);
             float rmag = 1.0f / mag;
 
             int n = (i * width + j) * 4;
             npixels[n]     = (unsigned char) (128 + 127 * dx * rmag);
-            npixels[n + 1] = (unsigned char) (128 - 127 * dy * rmag);
+            npixels[n + 1] = (unsigned char) (128 + 127 * dy * rmag);
             // npixels[n]     = (unsigned char) (128 + 127 * dy * rmag);
             // npixels[n + 1] = (unsigned char) (128 - 127 * dx * rmag);
             // npixels[n]     = (unsigned char) (128 - 127 * dx * rmag);