Local Ops: Deleting Faces & Healing Wounds

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Contents

• 14.1 Introduction
• 14.2 Methods for healing wounds
• 14.3 Healing faces with multiple loops
  • 14.3.1 Healing loops independently
• 14.4 Limitations/restrictions on healing wounds
• 14.5 Limitations/restrictions on growing loops together

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14.1 Introduction

PK_FACE_delete deletes faces from a body. Removing faces in this way leaves "wounds" that must be healed in order to leave the body in a valid state. The wound is actually a hole which has one or more loops.

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14.2 Methods for healing wounds

Wounds can be healed using the following methods:

Figure 14-1 Healing wounds - 'Grow from child' or 'Cap' using the loops_independent option

Figure 14-2 Healing wounds - 'Grow only'

Figure 14-3 Healing wounds - 'Allow shrinkage'

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14.3 Healing faces with multiple loops

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14.3.1 Healing loops independently

A further option that is available when healing wounds using the PK_FACE_delete operation, using either the grow or cap methods, and which is related to the treatment of the loops of the wounds.

If the option loops_independent is selected then each closed loop around a face is healed independently, otherwise loops are healed together. Healing loops independently can result in a fragmented body.

The following two examples, Figure 14-4 and Figure 14-5, show the results that are achieved when using both methods of healing multiple loops in conjunction with the 'Cap' and 'Allow shrinkage' options.

Figure 14-4 Deleting single shaded face

Figure 14-5 Deleting cylindrical and two planar faces

PK_FACE_delete receives a further option, "loops independent" which is applicable when the wound left has more than one loop.

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14.4 Limitations/restrictions on healing wounds

In the following example it is not possible to heal the wounds, in a single operation. This is because the 'face set' (i.e. the wound) is non-manifold. This operation is possible if the faces are deleted individually using the PK_FACE_heal_shrink_c option.

Figure 14-6 Non-manifold faceset boundary

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14.5 Limitations/restrictions on growing loops together

The following restrictions apply when growing loops together.

• It is only possible to grow across two loops simultaneously.
• It is not possible to grow across a wound with more than two loops.
• One of the two loops must lie on a single surface.
• The surface from the 'single surface loop' must intersect with all the surfaces from the other loop.
• The loop which lies on the single surface must not have vertices with three or more edges, see Figure 14-7.

Figure 14-7 Each of the two loops in the wound contains 3-edge vertices

• Only the face of the loop which lies on a single surface may be shrunk.

In the following example it is not possible to delete the planar face using the PK_FACE_heal_grow_from_parent_c option (healing the loops together) as this would shrink the faces on the rectangular block.

Figure 14-8 Cannot shrink faces not on the single surface

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