Sketch- and Constraint-based Design of B-spline Surfaces

Authors:
Paul Michalik, Dae Hyun Kim, Beat D. Bruderlin
Computer Graphics Group, Dept. of CS
Technical University of Ilmenau, Germany

Summary:
To join 2 splines- first the portion of the base curve relevant for merging is identified. Then merged with correction curve. A part to the left and right of base stroke is identified as the transition part, to give a gradual merging to the corrected curve.

Modes provided for 3D image editing:
1. Sweeping mode - mode to draw the initial set of curves
2. Skinning mode - to add curves to the already identified surfaces.
3. Sculpting mode
The sketch space. surface is showed using blue hatch lines. In the sculpting mode, each line drawn by the user leads to a constraint graph. each node is a constraint given by the user and the error calculated for the surface on the constraint. each node has weight associated with it which helps solve the over-constrained graphs.

Discussion:
the summary is not complete.. The lot of these mathematical modeling techniques expect the user to understand the maths behind it which might not be possible. This can affect the interaction between the user and the system considerably. A system that defines the method of user drawing constraints the user ability. "A good idea is to start with relatively simple surface, and let the system automatically introduce new DOFs at appropriate locations, if errors at the constraints exceed defined limits."