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Tree Cutting

5 min read

Tree Cutting #

The most common question is: How to add your own tree? Check the video!

Play

This is our quick walkthrough of the system check this one:

Play

We also added instant breakable trees like this video (but obvisouly peformant):

Play

We also have a full tutorial on our Udemy course within our survival framework on how to setup a basic tree cutting system from scratch.

cORE Principles of the tREECUTTING SYSTEM #

  • I have included two types of tree chopping logic. You choose which one you prefer.
    • Material Offset based on a static mesh. The only thing you must do is select your mesh in the configurable and it will work! It has fewer visual effects but is predictable and stable.
    • Chaos-based trees. Looks amazing! But needs some work to configure. Less predictable and stable.

Material offset based Tree #

The material offset based trees are static mesh only. You do not need to split it yourself,

To make a material offset based tree do the following:

  • Make a child of the master or copy paste a configuration:

  • Select your static mesh in the class defaults:

  • In that mesh, check which material is the base/trunk of the tree, open that one.

  • Now you already have the static mesh open, set allow CPU access on it.

  • Also remove any simple capsule collision and convert it to convex, play around with the settings to make it look nice. This will work for most trees. If it doesn't work for yours, you can just add a capsule collision and scale it.

  • On most trees this step is not needed, but on some mega scans trees it is:
  • Please make sure that your Configuration Blueprint has set the Choppable Material Index properly. To find it,
    • Open the tree Mesh
    • Highlight the part that needs to be chopped
    • Check which index it is on. This one is on Index 2

  • After you know the index, set that in the configuration blueprint.
    • I have made two predefined choppable material indexes. You can leave the second one if only one is applied.

  • Some trees also require setting the material indexes manually of the mesh after it is cut, you can override the materials on the top by checking the Boolean Set Top Mesh Manually:

  • In the trunk material that you are hitting with an axe (or master) add the MF_OffsetMask function which can be found in the material folder and connect it.

  • Now you are done, and it will work! Tweak settings in the class defaults to your liking

Chaos based #

Setting up the chaos tree is more advanced. Please only do if you know what you are doing!

  • Chaos based trees should consist of: Top, Middle, and a Trunk wherein the middle part is a destructible mesh.

  • Make a child of the configuration from the master or duplicate an existing one

  • Setup the class defaults and manually override the geometry collection (of course you need to make the collection first, check for chaos tutorials)

  • After you have setup all the defaults properly, test it out!

Actor Foliage vs PCG #

  • You can use the actor foliage to spawn it in the world via the foliage tool or use a pcg graph

  • However, since PCG is out and stable we strongly advise to use PCG. E.g. Our advanced Biome generator in combination with the mesh to actor swap system! Perfect for large scale worlds.

Use cases #

My tree breaks to fast or to slow, what to do? #

  • Chaos is heavily under development at Epic. On each update I see massive updates which also affects my assets. I’ve seen a couple of times that the mass calculation is changed which can cause issues of breaking down too fast or too slow. Gladly I made an option to easily change this.
  • NOTE: Currently it is made to process damage between ~10/50. Go the damage part later in this section to check it out if you use other values.
  • Open the child config of the tree you are hitting and notice the” mass required to be chopped down”

  • Hit the destructible object and check the mass that is printed. In this example, we see big numbers over the 4000 while we only needed 450 mass for the complete object to be destructed.

  • This means that when all pieces are broken, we have ~4000 massed chopped away. We probably want that somewhere over 50% of the total mass. We are going to experiment by trial and error to see what mass works for us.

  • Change the mass until you are satisfied with the result. Use the printed mass chopped down as an indicator of where to start with the mass.

  • Second part to consider is tweaking the amount of damage. I have the following code:

I only see Material Attributes in my material. How can I add the Material offset function? #

  • Some materials do have collapsed material attribute nodes like this

  • To add my MF_OffsetMask function you can break and make the nodes like this:

I am getting a Allow CPU access is not enabled error, what to do? #

  • If you do use my Material offset tree, and you get this error:

  • Please do open your specific mesh, and allow CPU Access

I have applied the material, but it does not seem to offset when hitting the tree #

Please make sure that your Configuration Blueprint has set the Choppable Material Index properly. To find it,

  • Open the tree Mesh
  • Highlight the part that needs to be chopped
  • Check which index it is on. This one is on Index 2

  • After you know the index, set that in the configuration blueprint.

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