Calculate derivative for slant palettes

src/main/java/com/dfsek/terra/config/base/ConfigPack.java

@@ -165,6 +165,7 @@ public class ConfigPack {
         biomeTemplates.forEach(biome -> {
             biomeRegistry.add(biome.getID(), biomeFactory.build(biome));
             Debug.info("Loaded biome " + biome.getID());
+            Debug.info("Threshold: " + biome.getSlantThreshold());
         });
 
         List<BiomeGridTemplate> biomeGridTemplates = new ArrayList<>();

src/main/java/com/dfsek/terra/config/templates/BiomeTemplate.java

@@ -65,14 +65,7 @@ public class BiomeTemplate implements ConfigTemplate {
     @Abstractable
     @Default
     private Palette<BlockData> oceanPalette = new SinglePalette<>(Material.WATER.createBlockData());
-    @Value("slant.y-offset.top")
-    @Abstractable
-    @Default
-    private double slantOffsetTop = 0.5D;
-    @Value("slant.y-offset-bottom")
-    @Abstractable
-    @Default
-    private double slantOffsetBottom = 0.25;
+
     @Value("elevation.equation")
     @Default
     @Abstractable
@@ -103,6 +96,15 @@ public class BiomeTemplate implements ConfigTemplate {
     @Default
     private Map<Material, Palette<BlockData>> stairPalettes;
 
+    @Value("slant.threshold")
+    @Abstractable
+    @Default
+    private double slantThreshold = 0.1;
+
+    public double getSlantThreshold() {
+        return slantThreshold;
+    }
+
     public double getSlabThreshold() {
         return slabThreshold;
     }
@@ -178,12 +180,4 @@ public class BiomeTemplate implements ConfigTemplate {
     public Map<Ore, OreConfig> getOres() {
         return ores;
     }
-
-    public double getSlantOffsetTop() {
-        return slantOffsetTop;
-    }
-
-    public double getSlantOffsetBottom() {
-        return slantOffsetBottom;
-    }
 }

src/main/java/com/dfsek/terra/generation/Sampler.java

@@ -0,0 +1,18 @@
+package com.dfsek.terra.generation;
+
+import net.jafama.FastMath;
+import org.polydev.gaea.math.ChunkInterpolator;
+
+public class Sampler {
+    private final ChunkInterpolator interpolator;
+    private final ElevationInterpolator elevationInterpolator;
+
+    public Sampler(ChunkInterpolator interpolator, ElevationInterpolator elevationInterpolator) {
+        this.interpolator = interpolator;
+        this.elevationInterpolator = elevationInterpolator;
+    }
+
+    public double sample(double x, double y, double z) {
+        return interpolator.getNoise(x, y - elevationInterpolator.getElevation(FastMath.roundToInt(x), FastMath.roundToInt(z)), z);
+    }
+}

src/main/java/com/dfsek/terra/generation/TerraChunkGenerator.java

@@ -9,6 +9,7 @@ import com.dfsek.terra.biome.palette.PaletteHolder;
 import com.dfsek.terra.config.base.ConfigPack;
 import com.dfsek.terra.config.lang.LangUtil;
 import com.dfsek.terra.config.templates.BiomeTemplate;
+import com.dfsek.terra.math.MathUtil;
 import com.dfsek.terra.population.CavePopulator;
 import com.dfsek.terra.population.FloraPopulator;
 import com.dfsek.terra.population.OrePopulator;
@@ -78,22 +79,10 @@ public class TerraChunkGenerator extends GaeaChunkGenerator {
         popMap.get(c.getWorld()).checkNeighbors(c.getX(), c.getZ(), c.getWorld());
     }
 
-    private static Palette<BlockData> getPalette(int x, int y, int z, BiomeTemplate c, ChunkInterpolator interpolator, ElevationInterpolator elevationInterpolator) {
+    private static Palette<BlockData> getPalette(int x, int y, int z, BiomeTemplate c, Sampler sampler) {
         PaletteHolder slant = c.getSlantPalette();
-        if(slant != null) {
-            double ySlantOffsetTop = c.getSlantOffsetTop();
-            double ySlantOffsetBottom = c.getSlantOffsetBottom();
-            boolean top = interpolator.getNoise(x, y + ySlantOffsetTop - elevationInterpolator.getElevation(x, z), z) > 0;
-            boolean bottom = interpolator.getNoise(x, y - ySlantOffsetBottom - elevationInterpolator.getElevation(x, z), z) > 0;
-
-            if(top && bottom) {
-                boolean north = interpolator.getNoise(x, y - elevationInterpolator.getElevation(x, z + 1), z + 1) > 0;
-                boolean south = interpolator.getNoise(x, y - elevationInterpolator.getElevation(x, z - 1), z - 1) > 0;
-                boolean east = interpolator.getNoise(x + 1, y - elevationInterpolator.getElevation(x + 1, z), z) > 0;
-                boolean west = interpolator.getNoise(x - 1, y - elevationInterpolator.getElevation(x - 1, z), z) > 0;
-
-                if((north || south || east || west) && (!(north && south && east && west))) return slant.getPalette(y);
-            }
+        if(slant != null && MathUtil.derivative(sampler, x, y, z) > c.getSlantThreshold()) {
+            return slant.getPalette(y);
         }
         return c.getPalette().getPalette(y);
     }
@@ -157,6 +146,8 @@ public class TerraChunkGenerator extends GaeaChunkGenerator {
             elevationInterpolator = new ElevationInterpolator(chunkX, chunkZ, tw.getGrid());
         }
 
+        Sampler sampler = new Sampler(interpolator, elevationInterpolator);
+
         for(byte x = 0; x < 16; x++) {
             for(byte z = 0; z < 16; z++) {
                 int paletteLevel = 0;
@@ -167,13 +158,11 @@ public class TerraChunkGenerator extends GaeaChunkGenerator {
                 Biome b = grid.getBiome(xOrig + x, zOrig + z, GenerationPhase.PALETTE_APPLY);
                 BiomeTemplate c = ((UserDefinedBiome) b).getConfig();
 
-                double elevate = elevationInterpolator.getElevation(x, z);
-
                 int sea = c.getSeaLevel();
                 Palette<BlockData> seaPalette = c.getOceanPalette();
                 for(int y = world.getMaxHeight() - 1; y >= 0; y--) {
-                    if(interpolator.getNoise(x, y - elevate, z) > 0) {
-                        BlockData data = getPalette(x, y, z, c, interpolator, elevationInterpolator).get(paletteLevel, cx, cz);
+                    if(sampler.sample(x, y, z) > 0) {
+                        BlockData data = getPalette(x, y, z, c, sampler).get(paletteLevel, cx, cz);
                         chunk.setBlock(x, y, z, data);
                         if(paletteLevel == 0 && c.doSlabs() && y < 255) {
                             prepareBlockPart(data, chunk.getBlockData(x, y + 1, z), chunk, new Vector(x, y + 1, z), c.getSlabPalettes(),

src/main/java/com/dfsek/terra/math/MathUtil.java

@@ -0,0 +1,20 @@
+package com.dfsek.terra.math;
+
+import com.dfsek.terra.generation.Sampler;
+
+public final class MathUtil {
+    private static final double CONST = 1;
+
+    public static double derivative(Sampler sampler, double x, double y, double z) {
+        double baseSample = sampler.sample(x, y, z);
+
+        double xVal1 = (sampler.sample(x + CONST, y, z) - baseSample) / CONST;
+        double xVal2 = (sampler.sample(x - CONST, y, z) - baseSample) / CONST;
+        double zVal1 = (sampler.sample(x, y, z + CONST) - baseSample) / CONST;
+        double zVal2 = (sampler.sample(x, y, z - CONST) - baseSample) / CONST;
+        double yVal1 = (sampler.sample(x, y + CONST, z) - baseSample) / CONST;
+        double yVal2 = (sampler.sample(x, y - CONST, z) - baseSample) / CONST;
+
+        return Math.sqrt(((xVal2 - xVal1) * (xVal2 - xVal1)) + ((zVal2 - zVal1) * (zVal2 - zVal1)) + ((yVal2 - yVal1) * (yVal2 - yVal1)));
+    }
+}