P41

Intersection Elimination

  • Let’s consider how to eliminate existing intersections, but without using any collision history.

  • Such a method is useful when there are already intersections in simulation, due to:

    • Past collision handling failures
    • Intense user interaction

  • In this case, we don’t require the simulation is to always intersection-free.

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.

方法一

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)

✅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：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。
✅ 此方法缺点：1. 无法处理边界；2. 难以在 GPU 上实 现；

P44

算法效果

Baraff et al. 2003. Untangling Cloth. TOG (SIGGRAPH)

✅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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https://caterpillarstudygroup.github.io/GAMES103_mdbook/