feat/fix: misc shader changes (fix normals, lighting, uv)

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

@@ -1,13 +1,17 @@
-float ao = smoothstep(0.0, 0.7, vGrassUv.y);
-ao = mix(0.05, 1.0, ao);
-
-vec3 rootColor = diffuseColor.rgb * 0.4;
-vec3 tipColor = diffuseColor.rgb * 1.5;
+float ao = smoothstep(0.0, 0.8, vGrassUv.y);
+ao = mix(0.15, 1.0, ao);
 
+vec3 rootColor = diffuseColor.rgb * 0.35;
+vec3 tipColor = diffuseColor.rgb * 1.3;
 vec3 grassColor = mix(rootColor, tipColor, vGrassUv.y);
-grassColor *= ao;
 
-float translucency = pow(vGrassUv.y, 2.0) * 0.5;
-grassColor += diffuseColor.rgb * translucency;
+vec3 viewDir = normalize(cameraPosition - vWorldPos);
+vec3 lightDir = normalize(vec3(15.0, 25.0, 15.0)); 
 
-diffuseColor.rgb = grassColor;
+float backLighting = max(0.0, dot(viewDir, -lightDir));
+backLighting = pow(backLighting, 3.0) * smoothstep(0.2, 1.0, vGrassUv.y);
+
+vec3 sssColor = vec3(0.4, 0.8, 0.3) * diffuseColor.rgb; 
+grassColor += sssColor * backLighting * 1.5;
+
+diffuseColor.rgb = grassColor * ao;