feat: overhaul grass

src/app/niko/scene-components/shaders/grass.frag

@@ -1,17 +1,31 @@
-float ao = smoothstep(0.0, 0.8, vGrassUv.y);
-ao = mix(0.15, 1.0, ao);
+float ao = smoothstep(0.0, 0.7, vGrassUv.y);
+ao = mix(0.05, 1.0, pow(ao, 1.6));
 
-vec3 rootColor = diffuseColor.rgb * 0.35;
-vec3 tipColor = diffuseColor.rgb * 1.3;
-vec3 grassColor = mix(rootColor, tipColor, vGrassUv.y);
+vec3 rootColor = diffuseColor.rgb * 0.15;
+vec3 midColor = diffuseColor.rgb;
+vec3 tipColor = diffuseColor.rgb * 1.3 + vec3(0.06, 0.08, 0.0);
+
+float heightParam = vGrassUv.y;
+vec3 grassColor;
+if (heightParam < 0.4) {
+    float t = smoothstep(0.0, 0.4, heightParam);
+    grassColor = mix(rootColor, midColor, t);
+} else {
+    float t = smoothstep(0.4, 1.0, heightParam);
+    grassColor = mix(midColor, tipColor, t);
+}
 
 vec3 viewDir = normalize(cameraPosition - vWorldPos);
-vec3 lightDir = normalize(vec3(15.0, 25.0, 15.0)); 
+vec3 lightDir = normalize(vec3(15.0, 25.0, 15.0));
 
-float backLighting = max(0.0, dot(viewDir, -lightDir));
-backLighting = pow(backLighting, 3.0) * smoothstep(0.2, 1.0, vGrassUv.y);
+float VdotL = max(0.0, dot(viewDir, -lightDir));
+float sss = pow(VdotL, 3.0) * smoothstep(0.2, 0.9, vGrassUv.y);
 
-vec3 sssColor = vec3(0.4, 0.8, 0.3) * diffuseColor.rgb; 
-grassColor += sssColor * backLighting * 1.5;
+vec3 sssColor = diffuseColor.rgb * vec3(0.6, 1.0, 0.15) * 1.8;
+grassColor += sssColor * sss * 2.0;
+
+float NdotV = 1.0 - max(0.0, dot(normalize(vNormal), viewDir));
+float rim = pow(NdotV, 3.0) * smoothstep(0.3, 1.0, vGrassUv.y) * 0.15;
+grassColor += vec3(0.3, 0.5, 0.1) * rim;
 
 diffuseColor.rgb = grassColor * ao;