Tim Hobson

Destruction with Rigid Animation

There may comes a time when you want to showcase some awesome destruction for your game and it's just not practical to have this simulated in real-time as a physically intractable scene. Another reason would be that you need the simulation to be the same each and every time without question and with as little overhead as possible. The PhysX Destructible system in Unreal Engine 4 simply cannot do this. Instead if you setup a physics simulation in your modeling application of choice you can export this. This tutorial will cover the basics of using this type of physics simulation in UE4 without the need to Skin, rig, or bone your mesh, but will not cover the creation for any specific software. 
This technique was used extensively in the Elemental demo's cinematic that you see in the beginning with the ceiling rocks crashing too the floor.
FBX and 3Ds Max file for reference: Download Files Here
This tutorial will demonstrate the beginning portion using 3DS Max. The process should be similar in other modeling applications.

Before your export the animation

​This is my mesh with the timeline animation that has already been baked from a physics simulation.
​Once you've got your animation setup the way that you would like you'll need to select all the Fracture chunks or pieces and place them in a group:

You can do this in Max by going to the menu bar > Group > Group > pop-up window > Give your group a name
  • ​After you've grouped your pieces we can export.
  • Select your group and choose Export Selected. 
  • Use these FBX settings, making sure that you include the animation. You can specify the exact frames you want to export if you'd like)
  • In my animation it is ~200 frames

Importing your rigid mesh animation into ue4

​When you import the FBX into UE4 make sure that you've selected the option for "Import as Skeletal" for this to work correctly. 

Use the following settings:

Using your Rigid mesh animation

​Place your skeletal mesh in your scene and create a reference to it in your Level BP and pull off a the pin to create a "Play Animation" Node. Select the animation and whether it should loop. 
​Then Play in Editor which should play like the video linked above.