P41
相交解除 Intersection Elimination
P42
对于有体积的物体
Eliminating cloth-volume and volume-volume intersections is straightforward: simply pushing vertices/edges in the volume out.

P43
对于没有体积的物体,Untangling Cloth问题
The situation is complicated in cloth-cloth intersection, since we don’t have a clear definition of inside and outside.
✅P42适用于有体积的物体,但布没有封闭体积,两根线没有里面外面之分,因此相交时不知道哪一段是正确的。
方法一
✅ 方法:对布分段,根据分段区域决定谁在上谁在下,以此为依据推动顶点。
算法过程
Baraff et al. used flood-fill to segment cloth into regions and decided which region is in intersection. (Cannot handle boundary well.)

Baraff et al. 2003. Untangling Cloth. TOG (SIGGRAPH)
P44
算法效果

✅缺点:1. 难以处理边界;2. 对整个面进行评估,难以用于GPU.
P45
方法二
Volino and Magnenat-Thalmann proposed to untangle cloth by reducing the
intersection contour.
Their method can handle boundaries, but it doesn’t always work.

✅ 两个面相交会产生一条曲线,目标是让曲线变短。优点:可以处理边界;缺点:基于局部优化、可用于 GPU。
✅可以处理边界情况,缩短边界也能解除相交。
P46
After-Class Reading
Volino and Magnenat-Thalmann et al. 2006. Resolving Surface Collisions through Intersection Contour Minimization. TOG (SIGGRAPH).
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