That looks distinctly like double-sided polygons. The normals are probably all facing the right way, but due to z-buffering issues, you are seeing some of the back faces and some of the front faces. You can either: 1. get rid of all the 'inside' polygons (the ones that are facing the inside of the garment). 2. add a displacement to the material that's applied to the outside layer of the dress. 3. disable back-face rendering.

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