How to Enviro Art: Tree Wind

(Enviro Art Lesson by Wolfgang Traenkle, Senior Enviro Artist)

Hey there! Wanted to make a quick page explaining how to get some cool movement in trees utilizing both vertex painting and an axis rotation in WPO

This video is the end result of using both methods:

• Using the axis rotation to make a sway

• Using Vertex paint to get the secondary movement that adds a noise to the tips of the leaves

Here is what the full BP looks like

Vertex: Secondary Wind

The Wind section is how you get the tips of the leaves to have that secondary noise, it uses a simple wind to add noise and then uses the Vertex color input to basically mask out the noise to just the tip of the leaf instead of everything.

1. In maya you are going to take you model and open the Apply color menu

2. To be able to start vertex painting you need to lay down a base layer, Just apply some flat black

3. Then Select all the edges that you want to wiggle, switch the color to white and apply. To be able to select vertex faster I like to do it in the UVs so I dont have to grab every edge individually

4. You should get results like this 

5. When importing into UE4 make sure you change the Vertex Color Import from the default IGNORE to REPLACE

AND WOW just like that you have leaves that wiggle, here is that visual

Sway: Axis rotation

This part of the BP is using the pivot of the object to rotation around the axis of the object creating an overall sway to the tree

 How the BP works

1. This section Normalizes the rotation axis in an up value so it is using the correct axis to rotate around

 2. This section creates two sine waves that creates variation in what direction the tree sways

3. This section establishes the location of the pivot point we want for where the object rotates from. We want the object to start its rotation from the bottom of the mesh  

 4. We want the overall affect of this sway to be determined independently, per object, wherever it is in the world so we will put an absolute world position in

 5. We dont want the whole tree to rotate evenly since the bottom of a tree is a lot more ridged. SO we take that pivot point that we established at the bottom of the mesh and combine that absolute world position so we can have that point in space no matter where it is places in the scene. Then you divide that in half to use only the top half of the tree

6. LASTLY, We add a constant sway option so that if instead of having the distance cut off be determined at the halfway point of each object, we can set it to be something like 1000 units away from the pivot. This makes it so the taller trees will have a sway that affects more of it than the smaller trees do.  

With all that said this is what it looks like with just the sway

 The final results with everything together!