Align terrain movement snowline parameters with shader and add polar land ice threshold

config/terrain_movement.yaml

@@ -7,8 +7,9 @@ mountain_rock_height_km: 2.3        # Height in km >= 2.3 is rocky mountain
 snow_height_km: 3.1                 # Altitude in km >= 3.1 is high peak snow
 polar_snow_line_enabled: true       # Whether latitude reduces snowline altitude
 polar_snow_line_base_km: 2.5        # Base snowline at temperate latitudes
-polar_snow_factor_start: 0.88       # Latitude distFromCenter where polar cooling starts (polar caps only)
-polar_snow_factor_end: 0.98         # Latitude distFromCenter where sea-level snowline is reached
+polar_snow_factor_start: 0.40       # Latitude distFromCenter where polar cooling starts (matches simple.frag)
+polar_snow_factor_end: 0.85         # Latitude distFromCenter where sea-level snowline is reached (matches simple.frag)
+polar_land_ice_threshold: 0.72      # Latitude distFromCenter where sea-level polar ice starts (matches simple.frag)
 
 # Slope and elevation movement penalties
 # Elevation difference (deltaH in km) between hex centers

terrainmovementmanager.cpp

@@ -12,8 +12,9 @@ TerrainMovementConfig::TerrainMovementConfig()
       snowHeightKm(3.1f),
       polarSnowLineEnabled(true),
       polarSnowLineBaseKm(2.5f),
-      polarSnowFactorStart(0.88f),
-      polarSnowFactorEnd(0.98f),
+      polarSnowFactorStart(0.40f),
+      polarSnowFactorEnd(0.85f),
+      polarLandIceThreshold(0.72f),
       uphillSlopeMultiplier(4.0f),
       downhillSlopeBonusMultiplier(2.0f),
       minStepCost(0.25f),
@@ -77,6 +78,9 @@ bool TerrainMovementManager::loadConfig(const QString &filePath)
     if (root.hasChild("polar_snow_factor_end")) {
         m_config.polarSnowFactorEnd = root["polar_snow_factor_end"].asFloat(0.85f);
     }
+    if (root.hasChild("polar_land_ice_threshold")) {
+        m_config.polarLandIceThreshold = root["polar_land_ice_threshold"].asFloat(0.72f);
+    }
 
     if (root.hasChild("uphill_slope_multiplier")) {
         m_config.uphillSlopeMultiplier = root["uphill_slope_multiplier"].asFloat(4.0f);
@@ -164,6 +168,13 @@ QString TerrainMovementManager::getTerrainType(int tx, int ty, Matrix2D<TerrainP
                 return "sneeuw";
             }
         }
+        if (distFromCenter >= m_config.polarLandIceThreshold) {
+            float tIce = std::max(0.0f, std::min(1.0f, (distFromCenter - m_config.polarLandIceThreshold) / 0.20f));
+            float polarLandIce = tIce * tIce * (3.0f - 2.0f * tIce);
+            if (polarLandIce > 0.5f) {
+                return "sneeuw";
+            }
+        }
     }
 
     // 4. Rocky mountain

terrainmovementmanager.h

@@ -41,6 +41,7 @@ struct TerrainMovementConfig {
     float polarSnowLineBaseKm;
     float polarSnowFactorStart;
     float polarSnowFactorEnd;
+    float polarLandIceThreshold;
 
     float uphillSlopeMultiplier;
     float downhillSlopeBonusMultiplier;