Local and Hierarchical Refinement for Subdivision Gradient Meshes

Gradient mesh design tools allow users to create detailed scalable images, traditionally through the creation and manipulation of a (dense) mesh with regular rectangular topology. Through recent advances it is now possible to allow gradient meshes to have arbitrary manifold topology, using a modified Catmull‐Clark subdivision scheme to define the resultant geometry and colour [ LKSD17 ]. We present two novel methods to allow local and hierarchical refinement of both colour and geometry for such subdivision gradient meshes. Our methods leverage the mesh properties that the particular subdivision scheme ensures. In both methods, the artists enjoy all the standard capabilities of manipulating the mesh and the associated colour gradients at the coarsest level as well as locally at refined levels. Further novel features include interpolation of both position and colour of the vertices of the input meshes, local detail follows coarser‐level edits, and support for sharp colour transitions, all at any level in the hierarchy offered by subdivision.

[1]  Paul L. Rosin,et al.  Image and Video-Based Artistic Stylisation , 2012, Computational Imaging and Vision.

[2]  Neil A. Dodgson,et al.  Control vectors for splines , 2015, Comput. Aided Des..

[3]  Pascal Barla,et al.  Gradient Art: Creation and Vectorization , 2013, Image and Video-Based Artistic Stylisation.

[4]  Tony DeRose,et al.  Subdivision surfaces in character animation , 1998, SIGGRAPH.

[5]  Harry Shum,et al.  Image vectorization using optimized gradient meshes , 2007, ACM Trans. Graph..

[6]  Thomas J. R. Hughes,et al.  Extended Truncated Hierarchical Catmull–Clark Subdivision , 2016 .

[7]  Jiansong Deng,et al.  Truncated Hierarchical Loop Subdivision Surfaces and application in isogeometric analysis , 2016, Comput. Math. Appl..

[8]  Adobe Creative Team Adobe Illustrator 8 Classroom in a Book , 1998 .

[9]  E. Catmull,et al.  Recursively generated B-spline surfaces on arbitrary topological meshes , 1978 .

[10]  Neil A. Dodgson,et al.  A Colour Interpolation Scheme for Topologically Unrestricted Gradient Meshes , 2017, Comput. Graph. Forum.

[11]  Tony DeRose,et al.  Efficient, fair interpolation using Catmull-Clark surfaces , 1993, SIGGRAPH.

[12]  Rémi Ronfard,et al.  Vector graphics animation with time-varying topology , 2015, ACM Trans. Graph..

[13]  Pascal Barla,et al.  Diffusion curves: a vector representation for smooth-shaded images , 2008, ACM Trans. Graph..

[14]  Yizhou Yu,et al.  Patch-based image vectorization with automatic curvilinear feature alignment , 2009, ACM Trans. Graph..

[15]  Tony DeRose,et al.  Feature-adaptive GPU rendering of Catmull-Clark subdivision surfaces , 2012, TOGS.

[16]  Ralph R. Martin,et al.  Automatic and topology-preserving gradient mesh generation for image vectorization , 2009, SIGGRAPH 2009.

[17]  Ralph R. Martin,et al.  Automatic and topology-preserving gradient mesh generation for image vectorization , 2009, ACM Trans. Graph..

[18]  David A. Forsyth,et al.  A Subdivision-Based Representation for Vector Image Editing , 2012, IEEE Transactions on Visualization and Computer Graphics.

[19]  Jirí Kosinka,et al.  Locally refinable gradient meshes supporting branching and sharp colour transitions , 2018, The Visual Computer.

[20]  William A. Barrett,et al.  Object-based vectorization for interactive image editing , 2006, The Visual Computer.

[21]  Lei Wei,et al.  Representing Images Using Curvilinear Feature Driven Subdivision Surfaces , 2014, IEEE Transactions on Image Processing.

[22]  Neil A. Dodgson,et al.  Shading Curves: Vector‐Based Drawing With Explicit Gradient Control , 2015, Comput. Graph. Forum.

[23]  Henrik Lieng,et al.  A gradient mesh tool for non-rectangular gradient meshes , 2017, SIGGRAPH Posters.

[24]  Charles T. Loop,et al.  Smooth Subdivision Surfaces Based on Triangles , 1987 .

[25]  David R. Forsey,et al.  Hierarchical B-spline refinement , 1988, SIGGRAPH.

[26]  John Snyder,et al.  Freeform vector graphics with controlled thin-plate splines , 2011, ACM Trans. Graph..