diff --git a/apps/opencs/model/world/data.cpp b/apps/opencs/model/world/data.cpp
index 470ce04131..4198e1b980 100644
--- a/apps/opencs/model/world/data.cpp
+++ b/apps/opencs/model/world/data.cpp
@@ -152,6 +152,7 @@ CSMWorld::Data::Data(ToUTF8::FromType encoding, const Files::PathContainer& data
     mResourceSystem
         = std::make_unique<Resource::ResourceSystem>(mVFS.get(), expiryDelay, &mEncoder.getStatelessEncoder());
 
+    // FIXME: this is severely out of date (see #7595)
     Shader::ShaderManager::DefineMap defines
         = mResourceSystem->getSceneManager()->getShaderManager().getGlobalDefines();
     Shader::ShaderManager::DefineMap shadowDefines = SceneUtil::ShadowManager::getShadowsDisabledDefines();
diff --git a/apps/openmw/mwrender/renderingmanager.cpp b/apps/openmw/mwrender/renderingmanager.cpp
index dc71e455b2..d5c5321f8e 100644
--- a/apps/openmw/mwrender/renderingmanager.cpp
+++ b/apps/openmw/mwrender/renderingmanager.cpp
@@ -446,6 +446,7 @@ namespace MWRender
         globalDefines["useOVR_multiview"] = "0";
         globalDefines["numViews"] = "1";
         globalDefines["disableNormals"] = "1";
+        globalDefines["reconstructNormalZ"] = "0";
 
         for (auto itr = lightDefines.begin(); itr != lightDefines.end(); itr++)
             globalDefines[itr->first] = itr->second;
diff --git a/components/resource/imagemanager.cpp b/components/resource/imagemanager.cpp
index a7d2ef61a1..e7cc9f03e5 100644
--- a/components/resource/imagemanager.cpp
+++ b/components/resource/imagemanager.cpp
@@ -78,8 +78,7 @@ namespace Resource
                 }
                 break;
             }
-            // not bothering with checks for other compression formats right now, we are unlikely to ever use those
-            // anyway
+            // not bothering with checks for other compression formats right now
             default:
                 return true;
         }
diff --git a/components/shader/shadervisitor.cpp b/components/shader/shadervisitor.cpp
index 7bce9de2a6..3867f1f43e 100644
--- a/components/shader/shadervisitor.cpp
+++ b/components/shader/shadervisitor.cpp
@@ -184,6 +184,7 @@ namespace Shader
         , mAdditiveBlending(false)
         , mDiffuseHeight(false)
         , mNormalHeight(false)
+        , mReconstructNormalZ(false)
         , mTexStageRequiringTangents(-1)
         , mSoftParticles(false)
         , mNode(nullptr)
@@ -429,6 +430,7 @@ namespace Shader
                     normalMapTex->setFilter(osg::Texture::MAG_FILTER, diffuseMap->getFilter(osg::Texture::MAG_FILTER));
                     normalMapTex->setMaxAnisotropy(diffuseMap->getMaxAnisotropy());
                     normalMapTex->setName("normalMap");
+                    normalMap = normalMapTex;
 
                     int unit = texAttributes.size();
                     if (!writableStateSet)
@@ -440,6 +442,23 @@ namespace Shader
                     mRequirements.back().mNormalHeight = normalHeight;
                 }
             }
+
+            if (normalMap != nullptr && normalMap->getImage(0))
+            {
+                // Special handling for red-green normal maps (e.g. BC5 or R8G8).
+                switch (normalMap->getImage(0)->getPixelFormat())
+                {
+                    case GL_RG:
+                    case GL_RG_INTEGER:
+                    case GL_COMPRESSED_RED_GREEN_RGTC2_EXT:
+                    case GL_COMPRESSED_SIGNED_RED_GREEN_RGTC2_EXT:
+                    {
+                        mRequirements.back().mReconstructNormalZ = true;
+                        mRequirements.back().mNormalHeight = false;
+                    }
+                }
+            }
+
             if (mAutoUseSpecularMaps && diffuseMap != nullptr && specularMap == nullptr && diffuseMap->getImage(0))
             {
                 std::string specularMapFileName = diffuseMap->getImage(0)->getFileName();
@@ -629,6 +648,7 @@ namespace Shader
 
         defineMap["diffuseParallax"] = reqs.mDiffuseHeight ? "1" : "0";
         defineMap["parallax"] = reqs.mNormalHeight ? "1" : "0";
+        defineMap["reconstructNormalZ"] = reqs.mReconstructNormalZ ? "1" : "0";
 
         writableStateSet->addUniform(new osg::Uniform("colorMode", reqs.mColorMode));
         addedState->addUniform("colorMode");
diff --git a/components/shader/shadervisitor.hpp b/components/shader/shadervisitor.hpp
index a8e79ec995..9ce0819bd3 100644
--- a/components/shader/shadervisitor.hpp
+++ b/components/shader/shadervisitor.hpp
@@ -110,6 +110,7 @@ namespace Shader
 
             bool mDiffuseHeight; // true if diffuse map has height info in alpha channel
             bool mNormalHeight; // true if normal map has height info in alpha channel
+            bool mReconstructNormalZ; // used for red-green normal maps (e.g. BC5)
 
             // -1 == no tangents required
             int mTexStageRequiringTangents;
diff --git a/files/shaders/compatibility/bs/default.frag b/files/shaders/compatibility/bs/default.frag
index 77131c6a52..d2c8de0b22 100644
--- a/files/shaders/compatibility/bs/default.frag
+++ b/files/shaders/compatibility/bs/default.frag
@@ -77,6 +77,9 @@ void main()
     vec3 specularColor = getSpecularColor().xyz;
 #if @normalMap
     vec4 normalTex = texture2D(normalMap, normalMapUV);
+#if @reconstructNormalZ
+    normalTex.z = sqrt(1.0 - dot(normalTex.xy, normalTex.xy));
+#endif
     vec3 viewNormal = normalToView(normalTex.xyz * 2.0 - 1.0);
     specularColor *= normalTex.a;
 #else
diff --git a/files/shaders/compatibility/groundcover.frag b/files/shaders/compatibility/groundcover.frag
index dfdd6518c3..aab37d465d 100644
--- a/files/shaders/compatibility/groundcover.frag
+++ b/files/shaders/compatibility/groundcover.frag
@@ -59,7 +59,11 @@ void main()
     gl_FragData[0].a = alphaTest(gl_FragData[0].a, alphaRef);
 
 #if @normalMap
-    vec3 viewNormal = normalToView(texture2D(normalMap, normalMapUV).xyz * 2.0 - 1.0);
+    vec4 normalTex = texture2D(normalMap, normalMapUV);
+#if @reconstructNormalZ
+    normalTex.z = sqrt(1.0 - dot(normalTex.xy, normalTex.xy));
+#endif
+    vec3 viewNormal = normalToView(normalTex.xyz * 2.0 - 1.0);
 #else
     vec3 viewNormal = normalToView(normalize(passNormal));
 #endif
diff --git a/files/shaders/compatibility/objects.frag b/files/shaders/compatibility/objects.frag
index 56c7abf27c..eb5b79a0c2 100644
--- a/files/shaders/compatibility/objects.frag
+++ b/files/shaders/compatibility/objects.frag
@@ -167,7 +167,11 @@ vec2 screenCoords = gl_FragCoord.xy / screenRes;
     gl_FragData[0].a = alphaTest(gl_FragData[0].a, alphaRef);
 
 #if @normalMap
-    vec3 viewNormal = normalToView(texture2D(normalMap, normalMapUV + offset).xyz * 2.0 - 1.0);
+    vec4 normalTex = texture2D(normalMap, normalMapUV + offset);
+#if @reconstructNormalZ
+    normalTex.z = sqrt(1.0 - dot(normalTex.xy, normalTex.xy));
+#endif
+    vec3 viewNormal = normalToView(normalTex.xyz * 2.0 - 1.0);
 #else
     vec3 viewNormal = normalize(gl_NormalMatrix * passNormal);
 #endif
diff --git a/files/shaders/compatibility/terrain.frag b/files/shaders/compatibility/terrain.frag
index abc7425eb0..f45f1f024e 100644
--- a/files/shaders/compatibility/terrain.frag
+++ b/files/shaders/compatibility/terrain.frag
@@ -63,7 +63,11 @@ void main()
 #endif
 
 #if @normalMap
-    vec3 viewNormal = normalToView(texture2D(normalMap, adjustedUV).xyz * 2.0 - 1.0);
+    vec4 normalTex = texture2D(normalMap, adjustedUV);
+#if @reconstructNormalZ
+    normalTex.z = sqrt(1.0 - dot(normalTex.xy, normalTex.xy));
+#endif
+    vec3 viewNormal = normalToView(normalTex.xyz * 2.0 - 1.0);
 #else
     vec3 viewNormal = normalize(gl_NormalMatrix * passNormal);
 #endif