Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Poisson Vector Graphics (PVG) and Its Closed-Form Solver   This paper presents Poisson vector graphics, an extension of the popular
first-order diffusion curves, for generating smooth-shaded images. Armed with
two new types of primitives, namely Poisson curves and Poisson regions, PVG can
easily produce photorealistic effects such as specular highlights, core
shadows, translucency and halos. Within the PVG framework, users specify color
as the Dirichlet boundary condition of diffusion curves and control tone by
offsetting the Laplacian, where both controls are simply done by mouse click
and slider dragging. The separation of color and tone not only follows the
basic drawing principle that is widely adopted by professional artists, but
also brings three unique features to PVG, i.e., local hue change, ease of
extrema control, and permit of intersection among geometric primitives, making
PVG an ideal authoring tool.
  To render PVG, we develop an efficient method to solve 2D Poisson's equations
with piecewise constant Laplacians. In contrast to the conventional finite
element method that computes numerical solutions only, our method expresses the
solution using harmonic B-spline, whose basis functions can be constructed
locally and the control coefficients are obtained by solving a small sparse
linear system. Our closed-form solver is numerically stable and it supports
random access evaluation, zooming-in of arbitrary resolution and anti-aliasing.
Although the harmonic B-spline based solutions are approximate, computational
results show that the relative mean error is less than 0.3%, which cannot be
distinguished by naked eyes.

15
The categories of this paper are: nucl-ex
13
The categories of this paper are: quant-ph
27
The categories of this paper are: comp-gas
31
The categories of this paper are: ao-sci
9
The categories of this paper are: nlin
6
The categories of this paper are: astro-ph
24
The categories of this paper are: dg-ga
16
The categories of this paper are: stat
19
The categories of this paper are: eess
20
The categories of this paper are: acc-phys
34
The categories of this paper are: chem-ph
23
The categories of this paper are: solv-int
11
The categories of this paper are: hep-lat
12
The categories of this paper are: nucl-th
37
The categories of this paper are: supr-con
2
The categories of this paper are: math