  Head shapes play an important role in 3D character design. In this work, we
propose SimpModeling, a novel sketch-based system for helping users, especially
amateur users, easily model 3D animalmorphic heads - a prevalent kind of heads
in character design. Although sketching provides an easy way to depict desired
shapes, it is challenging to infer dense geometric information from sparse line
drawings. Recently, deepnet-based approaches have been taken to address this
challenge and try to produce rich geometric details from very few strokes.
However, while such methods reduce users' workload, they would cause less
controllability of target shapes. This is mainly due to the uncertainty of the
neural prediction. Our system tackles this issue and provides good
controllability from three aspects: 1) we separate coarse shape design and
geometric detail specification into two stages and respectively provide
different sketching means; 2) in coarse shape designing, sketches are used for
both shape inference and geometric constraints to determine global geometry,
and in geometric detail crafting, sketches are used for carving surface
details; 3) in both stages, we use the advanced implicit-based shape inference
methods, which have strong ability to handle the domain gap between freehand
sketches and synthetic ones used for training. Experimental results confirm the
effectiveness of our method and the usability of our interactive system. We
also contribute to a dataset of high-quality 3D animal heads, which are
manually created by artists.
