(转)CGMA - Organic World Building in UE4: week 6

原文：丢失，这篇是艺术家博客上发现的，小道整理笔记中，临时放于效果案例目录。

 
 

In this week we focused on creating the grass and flora to decorate your map. I used a bunch of Megascan assets I got from some time ago that I thought they worked well for the scene. We also created some roots we can use in our environment. I wanted to share with you some tips and advice I got during this week on creating foliage.

This is how the scene looks with some foliage on:

 
 

Foliage

I brake down the assets so that they can be used in different situations and can blend with the environment different.

These are some of the foliage I created for this scene:

As you can see, I have some big patches and some small patches. Also, different kinds of grass i grabbed from my references and some flowers I could use to break up the repetition when painting foliage. It's important to arrange the grass planes so that they go around a circle instead of a box. To speed up the workflow I used the Object Paint mode inside 3ds Max to paint different grass planes with different variations. I can then adjust them manually if I don't like the result but I found this was a good way to start creating the assets.

 
 

I would just play with the settings and find something I like that works for what I'm looking for. After that, I can save the preset and use it in the rest of the assets I want to create.

After that's done, I would adjust the vertex normals so they can blend nicely with the ground. I do that by using the Edit Normals tool and move them so that they can point upwards.

This is how the asset looks with the vertex normals changed:

This is how the asset looks without the vertex normals changed:

As you can see, the asset can blend nicely with the light when you change the normals. You can also transfer the vertex normals of a sphere and make it look nicer, which is something I may do to tweak the scene later on.

Finally, you want to add some vertex colors to mask the vertices you don't want to move when applying a vertex offset to simulate wind in the environment.

In this case, I painted green on the vertices I wanted to be affected by the wind and black for the vertices I wanted to stay still.

You want to have enough variations to have big, medium and small shapes. That way you can have really cool transitions in your environments and apply the same principle of Primary, Secondary and Tertiary shapes with all the assets you create.

For the Material, I'm using 4 textures: Albedo with opacity, SSS color, normals and a mask texture with roughness, height and spec map.

  
 

  
 

As you can see I'm using a Material parameter collection to change the values instead of using a common Parameter. The reason is that I want to iterate on all the assets at once to have an overall look of the scene. I can later change each material instance indivitualy but this is a good way to add global parameters to your scene. It can be used to change the roughness of all your assets in a rainy day or add a snow parameter on top. Really powerful stuff.

This is how my Material Parameter Collection looks like:

That way I can change global parameters in the scene like the snow:

Snow intensity at 2.1:

Snow intensity at 0:

I still need to change the textures so it can look nicer with the snow but it is a good start.

Roots

A great thing about the course is that Anthony teaches us how to create roots for your scene. They can make it look really believable and add an extra layer of complexity to the scene.

The way you create the roots is by using splines and then add some geometry and connect the vertices. You don't necessarily need to make a high poly model since the textures can do the work and also you can also smooth the mesh and add extra little details like bumps in the geometry to help sell the asset.

Here is a video when I show the process since it can be easier be explained there than a text:

 
 

After that is done, it is just a matter of UV the mesh so you can then apply some tiling materials on it and use an FFD modifier to rotate the mesh and create different variations. You can also use bones and skin the mesh to manipulate the roots individually.

This is how the mesh looks with the materials applied:

Here is how the material graph looks, it is simply blending 2 different materials using the slope shader:

 
 

 
 

Biggest takeaways:

• Foliage assets can bring a lot of life to your scene and they occupy a lot of screen space so it is a very important asset.
• Use different layers of complexity with your assets. Have some big grass patches, some smaller ones and use them to blend them nicely in your environment.
• Adding roots to your scene can help it look more natural and it is really easy to create them, so give it a try.