Figure 1: True2Form takes as input a 2D vector sketch, here traced on a design drawing (a). We formulate a set of local 3D regularity properties that our algorithm detects and applies selectively to lift the curves off the page into 3D (b). A baseline inaccurate 3D result (c, top), is gradually corrected by the selective regularization process (c, bottom). The accompanying histograms show how angles between all potentially parallel and locally symmetric curves are randomly spread initially but converge to a globally consistent state where these properties are either ignored or precisely enforced. For example, the curve tangents on the tapered fuselage are not treated as parallel in global context, despite being near-parallel in 2D (b, green cross). Our 3D curve network can be easily surfaced to bring the sketch to life or integrate the airplane design with its drive-train (d). Airplane sketch by Spencer Nugent. True2Form is a sketch-based modeling system that reconstructs 3D curves from typical design sketches. Our approach to infer 3D form from 2D drawings is a novel mathematical framework of insights derived from perception and design literature. We note that designers favor viewpoints that maximally reveal 3D shape information, and strategically sketch descriptive curves that convey intrinsic shape properties, such as curvature, symmetry, or parallelism. Studies indicate that viewers apply these properties selectively to envision a globally consistent 3D shape. We mimic this selective regularization algorithmically, by progressively detecting and enforcing applicable properties, accounting for their global impact on an evolving 3D curve network. Balancing regularity enforcement against sketch fidelity at each step allows us to correct for inaccuracy inherent in free-hand sketching. We perceptually validate our approach by showing agreement between our algorithm and viewers in selecting applicable regularities. We further evaluate our solution by: reconstructing a range of 3D models from diversely sourced sketches; comparisons to prior art; and visual comparison to both ground-truth and 3D reconstructions by designers.
Other assisted sketching systems take as input 2D sketches and interpret them as 3D curve networks REF .
True2Form: 3D curve networks from 2D sketches via selective regularization
TOGS
Computer Science