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The Unpaste op removes one or more pasted surfaces from a paste hierarchy, causing the hierarchy to update. It can keep either the unpasted surfaces or what remains pasted in the hierarchy after the removal of the unpasted surfaces.
The op accepts both pasted surfaces and entire paste hierarchies as inputs. For example, to turn a paste hierarchy into a set of unrelated surfaces, enter the hierarchy number in the Group field.
By preserving the hierarchical structure of the unpasted surfaces, the resulting sub-hierarchy can be reapplied properly to another hierarchy later on.
The shape and the size of the sub-hierarchy may change considerably as a result of the unpasting operation. This is because the feature surfaces are always mapped onto the domain of the base surface, and the size of the domain is completely unrelated to the size of the actual surface.
By unpasting the root of the paste hierarchy the whole hierarchy becomes undone.
Unpasted Surface Hierarchies
An unpasted surface or sub-hierarchy can be repasted later with the Paste SOP. One case of repasting is worth mentioning for its practical use.
Assume you have used the Paste op to spawn a new surface as a detail added to the base surface. Now you are ready to model the new feature. You can do so by working on the pasted feature, making sure to affect only its points and not the points of the base surface as well. If the point density of the model is high, it may be more convenient to model the feature separately, then re-attach it to the paste hierarchy as if it had never been removed.
There are three easy steps to achieve this goal:
Use the Unpaste op with the default parameters: keep the unpasted part and preserve the shape of the feature together with its hierarchical information. Make sure to specify the feature’s primitive number in the Group field. Notice the shape of the feature has not changed.
Model the stand-alone feature with Houdini’s vast array of tools.
Repaste the feature on the same base surface using the "As Is" tab with shape preservation enabled.
Subset of pasted surfaces or paste hierarchies
Include All Nested Children
Unpaste the surface with all its nested nodes
Keep Unpasted Part
Keep only the unpasted surface(s)
Preserve Pasted Shape
Preserve the shape they had when pasted
Preserve Hierarchical Structure
Extract as a new paste hierarchy
Keep Remaining Hierarchy
Delete the unpasted surface(s)