<H1>5 ANIMATING GARMENT WRINKLES</H1>
        Until now, the Geometric Wrinkle formulation is developed keeping in mind a general deformable model. In this section, we apply the method specifically for cloth animation. Figure 12 shows representative frames of a typical garment animation without Geometric Wrinkle. The garment is animated using a coarse mesh and low metric stiffnesses for the reasons explained in section 2. Though the user can design the wrinkles according to her wish, it is worthwhile to study the strain patterns in the garment. This is because, inappropriately placed wrinkles in the region where there is no deformation will not animate satisfactorily. In addition, the pattern should be orthogonal to the deformations in general, as explained in section 4.1. Figure 13 is a strain pattern for the second frame in the Figure 12 . Dark triangles are triangles with compression and depict the regions where wrinkles might appear. Based on such strain patterns (corresponding to two distinct frames of the garment animation in Figure 12 ), two wrinkling patterns are designed as shown in the Figure 14 . The patterns have distinct wrinkles and additional irregularities to smooth out the sharp appearance of wrinkles. Each pattern represents a distinct direction of deformation. Note that they are considerably orthogonal. Figure 17 (color plate) shows the result after applying the Geometric Wrinkles. It is interesting to see the smooth switch of the wrinkling patterns in the animation because of multi-fold wrinkling. Figure 15 and Figure 16 (color plates) use a single wrinkle pattern (different from Figure 14 ). The frames on the left side correspond to the animation without Geometric Wrinkles. Note that, there are very few wrinkles in the second figure as there is very little deformation of the mesh. The first figure shows the modulation of the wrinkles as per the deformation. As the calculations of the wrinkling coefficients are done on a per triangle basis, the computational time is linear with respect to number of triangles. Typically, it takes 5 minutes per thousand triangles on a MIPS R10000 200 MHz processor. Once the wrinkling coefficients are computed, the time spent on modulating wrinkle pattern is negligible compared to rendering time. In fact, for small meshes (upto a hundred polygons) the modulation of wrinkle pattern can be real time (20 fps).
        
          
          Figure 14: Wrinkling patterns for the garment
        
      
      
        