perlin noise generation and height maps

shaders/cube_frag.glsl

@@ -17,6 +17,8 @@ void main()
         // Dirt - brownish
         color *= vec3(0.6, 0.4, 0.2);
     } else if (v_VoxelKind == 2.0) {
+        color *= vec3(0.2, 0.8, 0.2);
+    } else if (v_VoxelKind == 3.0) {
         // Stone - grayish (keep as is)
     }