Discard terrain base layer alpha in non-shader rendering path (bug #6657)

CHANGELOG.md

@@ -17,6 +17,7 @@
     Bug #6427: Enemy health bar disappears before damaging effect ends
     Bug #6550: Cloned body parts don't inherit texture effects
     Bug #6645: Enemy block sounds align with animation instead of blocked hits
+    Bug #6657: Distant terrain tiles become black when using FWIW mod
     Bug #6661: Saved games that have no preview screenshot cause issues or crashes
     Bug #6807: Ultimate Galleon is not working properly
     Bug #6893: Lua: Inconsistent behavior with actors affected by Disable and SetDelete commands

components/terrain/material.cpp

@@ -173,6 +173,27 @@ namespace
         }
     };
 
+    class DiscardAlphaCombine
+    {
+    public:
+        static const osg::ref_ptr<osg::TexEnvCombine>& value()
+        {
+            static DiscardAlphaCombine instance;
+            return instance.mValue;
+        }
+
+    private:
+        osg::ref_ptr<osg::TexEnvCombine> mValue;
+
+        DiscardAlphaCombine()
+            : mValue(new osg::TexEnvCombine)
+        {
+            mValue->setCombine_Alpha(osg::TexEnvCombine::REPLACE);
+            mValue->setSource0_Alpha(osg::TexEnvCombine::CONSTANT);
+            mValue->setConstantColor(osg::Vec4(0.0, 0.0, 0.0, 1.0));
+        }
+    };
+
     class UniformCollection
     {
     public:
@@ -287,6 +308,8 @@ namespace Terrain
                     stateset->setTextureAttributeAndModes(
                         0, LayerTexMat::value(layerTileSize), osg::StateAttribute::ON);
 
+                stateset->setTextureAttributeAndModes(0, DiscardAlphaCombine::value(), osg::StateAttribute::ON);
+
                 // Multiply by the alpha map
                 if (!blendmaps.empty())
                 {