Monday, July 18, 2011

Cloth Cheat #2

It's been a while since I've talked about nCloth, so let's do that now.

I hope you all know about face normals.


Well, a normal tells you what direction a face is facing. You can see them by going to Display > Polygons > Face Normals. See those green things on one side? They're normals, telling you which direction the face is facing. (Hide them by going to the same place you went to make them appear).

The direction of your normals is really important when it comes to cloth simulation. Normals should always face out, for collision objects and cloth objects.

Why? Well, when you apply nCloth, and you want to adjust an attribute like Thickness, nCloth assumes that the normals are facing out and so, the thickness grows outward, in the direction the normal is facing. If your normals are facing the wrong way, your collisions will either fail or won't be nearly as accurate as they should.

Why? Let's continue to use Thickness as an example. Say you have a body and an article of clothing, a dress. Oops, the body's normals are facing inward. That means, the top of the body has no thickness. The dress will sink through until it reaches the thick part of the body, which is inside!

Indecent exposure. Pretty sure that's a no-no for any animated shot. (or maybe it isn't, in which case, I kinda want to see what you're working on...)

And this is just one attribute. Many other attributes depend on the direction of a face.

So what's the cheat?

Say you forgot to check your normals before you made your garment nCloth (shame!). You can't change them after the fact unless you remove nCloth, change the normals then reapply nCloth. What do you do now?


Let's continue to use Thickness as an example.

Instead of making the Thickness value 0.5, make it -0.5.

The thickness will grow from the bottom of the face rather than the top. It's a great cheat, especially if you're only working with one article of clothing.

I'll let you in on a little secret. If you look at the longest shot on my demo reel, the shot with the Nobleman and the Scribe walking away, I had to use this cheat on the Scribe's sleeves.



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