tune(environment): rebalance procedural grass zones

src/world/grass/GrassPatch.tsx

@@ -153,14 +153,17 @@ function createGrassMaterial(
       uClumpThreshold: { value: GRASS_CONFIG.clumpThreshold },
       uClumpSoftness: { value: GRASS_CONFIG.clumpSoftness },
       uZoneFrequency: { value: GRASS_CONFIG.zoneFrequency },
+      uNoGrassZoneThreshold: { value: GRASS_CONFIG.noGrassZoneThreshold },
       uSparseZoneThreshold: { value: GRASS_CONFIG.sparseZoneThreshold },
-      uTallZoneThreshold: { value: GRASS_CONFIG.tallZoneThreshold },
+      uMediumZoneThreshold: { value: GRASS_CONFIG.mediumZoneThreshold },
       uZoneSoftness: { value: GRASS_CONFIG.zoneSoftness },
+      uNoGrassZoneHeight: { value: GRASS_CONFIG.noGrassZoneHeight },
       uSparseZoneHeight: { value: GRASS_CONFIG.sparseZoneHeight },
-      uLowZoneHeight: { value: GRASS_CONFIG.lowZoneHeight },
+      uMediumZoneHeight: { value: GRASS_CONFIG.mediumZoneHeight },
       uTallZoneHeight: { value: GRASS_CONFIG.tallZoneHeight },
+      uNoGrassZoneDensity: { value: GRASS_CONFIG.noGrassZoneDensity },
       uSparseZoneDensity: { value: GRASS_CONFIG.sparseZoneDensity },
-      uLowZoneDensity: { value: GRASS_CONFIG.lowZoneDensity },
+      uMediumZoneDensity: { value: GRASS_CONFIG.mediumZoneDensity },
       uTallZoneDensity: { value: GRASS_CONFIG.tallZoneDensity },
       uMaxBendAngle: { value: GRASS_CONFIG.maxBendAngle },
       uMaxBladeHeight: { value: GRASS_CONFIG.maxBladeHeight },

src/world/grass/grassConfig.ts

@@ -17,14 +17,17 @@ export const GRASS_CONFIG = {
   clumpThreshold: 0.18,
   clumpSoftness: 0.45,
   zoneFrequency: 0.035,
+  noGrassZoneThreshold: 0.2,
   sparseZoneThreshold: 0.4,
-  tallZoneThreshold: 0.8,
+  mediumZoneThreshold: 0.65,
   zoneSoftness: 0.08,
+  noGrassZoneHeight: 0,
   sparseZoneHeight: 0.08,
-  lowZoneHeight: 0.45,
+  mediumZoneHeight: 0.45,
   tallZoneHeight: 1,
+  noGrassZoneDensity: 0,
   sparseZoneDensity: 0.08,
-  lowZoneDensity: 0.72,
+  mediumZoneDensity: 0.72,
   tallZoneDensity: 1,
   maxBendAngle: 14,
 } as const;

src/world/grass/grassShaders.ts

@@ -26,14 +26,17 @@ export const grassVertexShader = /* glsl */ `
   uniform float uClumpThreshold;
   uniform float uClumpSoftness;
   uniform float uZoneFrequency;
+  uniform float uNoGrassZoneThreshold;
   uniform float uSparseZoneThreshold;
-  uniform float uTallZoneThreshold;
+  uniform float uMediumZoneThreshold;
   uniform float uZoneSoftness;
+  uniform float uNoGrassZoneHeight;
   uniform float uSparseZoneHeight;
-  uniform float uLowZoneHeight;
+  uniform float uMediumZoneHeight;
   uniform float uTallZoneHeight;
+  uniform float uNoGrassZoneDensity;
   uniform float uSparseZoneDensity;
-  uniform float uLowZoneDensity;
+  uniform float uMediumZoneDensity;
   uniform float uTallZoneDensity;
   uniform float uMaxBendAngle;
   uniform float uMaxBladeHeight;
@@ -88,16 +91,23 @@ export const grassVertexShader = /* glsl */ `
     float clumpNoise = texture2D(uNoiseTexture, clumpUv).r;
     float clumpMask = smoothstep(uClumpThreshold, uClumpThreshold + uClumpSoftness, clumpNoise);
     float zoneNoise = texture2D(uNoiseTexture, worldPos.xz * uZoneFrequency).r;
-    float sparseZone = 1.0 - smoothstep(uSparseZoneThreshold, uSparseZoneThreshold + uZoneSoftness, zoneNoise);
-    float tallZone = smoothstep(uTallZoneThreshold, uTallZoneThreshold + uZoneSoftness, zoneNoise);
-    float midZone = clamp(1.0 - sparseZone - tallZone, 0.0, 1.0);
+    float noGrassZone = 1.0 - smoothstep(uNoGrassZoneThreshold, uNoGrassZoneThreshold + uZoneSoftness, zoneNoise);
+    float sparseZone =
+      smoothstep(uNoGrassZoneThreshold, uNoGrassZoneThreshold + uZoneSoftness, zoneNoise) *
+      (1.0 - smoothstep(uSparseZoneThreshold, uSparseZoneThreshold + uZoneSoftness, zoneNoise));
+    float mediumZone =
+      smoothstep(uSparseZoneThreshold, uSparseZoneThreshold + uZoneSoftness, zoneNoise) *
+      (1.0 - smoothstep(uMediumZoneThreshold, uMediumZoneThreshold + uZoneSoftness, zoneNoise));
+    float tallZone = smoothstep(uMediumZoneThreshold, uMediumZoneThreshold + uZoneSoftness, zoneNoise);
     float zoneHeight =
+      noGrassZone * uNoGrassZoneHeight +
       sparseZone * uSparseZoneHeight +
-      midZone * uLowZoneHeight +
+      mediumZone * uMediumZoneHeight +
       tallZone * uTallZoneHeight;
     float zoneDensity =
+      noGrassZone * uNoGrassZoneDensity +
       sparseZone * uSparseZoneDensity +
-      midZone * uLowZoneDensity +
+      mediumZone * uMediumZoneDensity +
       tallZone * uTallZoneDensity;
     float bladeVisibility = step(random(worldPos.xz), zoneDensity);
     float heightModifier = uMaxBladeHeight * mix(0.35, 1.0, heightNoiseAverage) * uHeightNoiseAmplitude;