SnapPaste: An Interactive Technique for Easy Mesh Composition

Andrei Sharf, Marina Blumenkrants, Ariel Shamir, Daniel Cohen–Or

Snapping allows even eight years old children to compose 3D mesh parts easily.

Abstract:

Editing and manipulation of existing 3D geometric objects are means to extend their repertoire and promote their availability. Traditionally, tools to compose or manipulate objects defined by 3D meshes are in the realm of artists and experts. In this paper, we introduce a simple and effective user interface for easy composition of 3D mesh-parts for non-professionals. Our technique borrows from the cut-and-paste paradigm where a user can cut parts out of existing objects and paste them onto others to create new designs. To assist the user attach objects to each other in a quick and simple manner, many applications in computer graphics support the notion of “snapping”. Similarly, our tool allows the user to loosely drag one mesh part onto another with an overlap, and lets the system snap them together in a graceful manner. Snapping is accomplished using our Soft-ICP algorithm which replaces the global transformation in the ICP algorithm with a set of point-wise locally supported transformations. The technique enhances registration with a set of rigid to elastic transformations that account for simultaneous global positioning and local blending of the objects. For completeness of our framework, we present an additional simple mesh-cutting tool, adapting the graph-cut algorithm to meshes.

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Movie:
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The Soft-ICP algorithm: Starting with one shape placed near another with an overlap, correspondence is computed in the snapping region (gray region) (left). Transformations are computed point-wise (example shows for 3 points), based on local supporting neighborhoods (colored stripes) (middle). The algorithm iteratively computes correspondence and transformations on both shapes until they gracefully blend together (right). Note the elastic deformation inside the snapping region while details outside rigidly align.

Differences in the speed of the pasting gesture: colors of the heads denote the dragging speed, the darker the color, the more slowly the positioning is. The snapping process has more freedom in relative positioning as the pasting is faster. Dragging the shapes slowly causes the shapes to merge with little change in the global position.

Sphinx’s face lift. A part of the Sphinx’s face is loosely cut out and replaced. Snapping aligns and merges the replacing part in a natural manner.

Snapping multiple boundaries simultaneously can only be achieved by a technique that treats the surface locally as a soft body and does not require exact positioning.