A constraint-based manipulator toolset for editing 3D objects
Ching-Yao Hsu, G. Alt, Zhengdong Huang, Ekkehard Beier, Beat D. Bruderlin · 1997
We present TWEAK, a new constraint-based manipulator tool set for editing CAD models.Manipulators for positioning vertices, translating and orienting planes, and for translating and orienting rigid objects, appear on the graphic elements that are picked by the interactive user.These manipulators may be controlled by dragging handles.They are connected to an efficient three-dimensional geometric constraint solver, which ensures that the changes are consistent with the relationships defined between the geometric elements of the model.The manipulators can also be used to snap together objects to build assemblies, and they serve as temporary constraints to explicitly control the behavior of the constraint system in underconstrained situations.The manipulators also provide an optional grid system, discretizing the transformations and dimensions.The multiple functionality of the manipulators makes modifications of CAD models easy and intuitive, and at the same time, they provide the necessary accuracy.A few mouse clicks and drag operations can achieve what previously required a complex sequence of operations in CAD systems.