Here's how i created this little animation:
tree: i used the free treeIt software to create the trunk and the basic shape of the tree. as for the leaves i created an alpha mask using Photoshop. there's a very good tutorial on this subject. finally i imported everything into unreal and made a tree leaves material and applied it to the leaves. i created bunch of leaves alphas so that i could have some flexibility in terms of variation.
grass: i modelled some basic grass strands in blender and made sure their normals were correct. and then i imported them into unreal. made a basic stylized grass material following some tuts on YouTube. i wanted to use unreal's runtime virtual texture for my grass strands so that the grass follows the color of the landscape.
landscape: this was the easiest part. created a landscape and made a landscape material driven by virtual texture. did some little sculpting and it was done.
painted the grass on the landscape, placed the tree, used Niagara system for the rain, played with lighting settings for a day and finally, rendered out some clips.
some useful tuts link : • Stylized Grass Tutorial
• Stylized Tree Tutorial