CC3 Cloth simulation in iClone and Unreal Engine 4

Oct 02, 2021 at 06:00 am by nemirc

Turning a cloth object into a dynamic cloth object in CC3 is pretty easy, but it may require some experimentation to get the result you want. All you need to do is select the cloth object you want to turn into a dynamic object, and then go to the PhysX tab (the one that looks like an atom in the Modify pane).

Then, click on the Weight Map button and a pop-up window will open, where you can import a weight map. Weight maps are grayscale maps that tell the cloth what is dynamic and what is static. Static parts are painted black, while different shades of gray will offer different degree of simulation (whiter parts move more).

As you can see, the gradient is not uniform (frontal parts of the UVs are placed at a different height than rear parts). For this reason, I decided to paint the weight map in Substance Designer.

First, I used a Tri Planar node to project a gradient along the vertical axis (I modified the gradient so the upper part of the dress was solid white and then the lower part gradually turned black).

Then, I used a mask to combine the result of the Tri Planer and a solid color, to make sure only the lower part has a gradient applied and the upper part is completely solid. I considered this necessary because there might be the chance the re was some gradient in the parts I didn’t want to become dynamic.

And lastly, I used an invert node.

This process is the one you have to use to make dynamic clothing for iClone. The dress animates just fine, without the need of any extra work. However, in iClone you have some extra settings you can use to tweak your cloth simulation even further. You can select a cloth preset, or you can manually configure settings to tweak your cloth simulation (on a side note, there are also presets for hair and wind forces).

Below you can see an animation of this elf woman with the dress.

Another thing you can do is tweak collisions of your character. You can resize colliders and add new colliders as you see fit.

On top of this, this setup automatically adds cloth simulation to your CC3 characters in Unreal Engine 4. If you export your CC3 character into Unreal Engine 4, the auto-setup will automatically add cloth simulation to the dynamic outfit. However, the default Physics Asset is not really that good (this asset is automatically created by UE4), so you need to manually create a new Physics Asset for your cloth simulation. For example, for this dress I used a lot of capsule and sphere colliders to simulate the shape of my character’s hips and buttocks.

This is how the simulation looks in UE4. Keep in mind OBS for some reason makes the game run a little slower. If I had not been using a video capture software, the game would have ran faster and the cloth wouldn't have gotten through her skin.

Since the character in Just Let Me Go has various outfits, I used the same technique for some flared leggings she has. What I did is left everything from the waist to the knees completely black, and then I used a gradient to make the lower part of the leggings dynamic.

I hope these techniques were useful and I hope to see some of your iClone work in the Renderosity gallery!


Sections: Tips + Tutorials

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