This code performs gradient domain processing [Chuang et al. 2009, Chuang et al. 2016] on signals defined on a mesh, where the signal can be either a color-field represented as a color per vertex or is the position of the vertices themselves. The code supports both sharpening and smoothing of the signals through the solution of a screened-Poisson equation. Specifically, given an input signal F, it solves for the signal G minimizing:

For more robust estimation of normals, the executable also supports harmonic smoothing of normals as described in [Prada et al. 2016]. As with the code above, this amounts to minimizing:

In the case that the signal processed describes the vertices' normals, we also support fitting the original geometry to the processed normals using the approach of [Yu et al. 2004]. Given input positions F and a target normal field N This amounts to minimizing:

ShapeGradientDomain: Processes either the vertex positions, or per-vertex colors, performing isotropic/anisotropic gradient-domain smoothing and sharpening (with the option of smoothing normals in a pre-processing step)

--in <input geometry>

This string specifies the name of the input geometry, represented in PLY format.

[--out <ouput geometry>]

This string specifies the name of the output geometry, represented in PLY format.

[--nIters <normal smoothing iterations>]

This integer value gives the number of iterations of harmonic normal smoothing to be performed before estimating curvatures. (If normal smoothing is desired, we have found that a single iteration suffices.)
The default value for this parameter is 0.

[--nTime <normal diffusion time>]

This floating point value gives the normal diffusion time (γ).
The default value for this parameter is 10^-4.

[--gWeight <gradient interpolation weight>]

This floating point value gives the weight for gradient interpolation (β).
The default value for this parameter is 10^-4.

[--gScale <gradient scale>]

This floating point value gives the scale factor for the target gradient field (λ).
The default value for this parameter is 1.0.

[--kWeight <curvature weight>]

This floating point value gives the curvature weight for adjusting the metric (ε).
The default value for this parameter is 0.0.

[--npWeight <normal projection weight>]

This floating point value gives the normal projection weight (δ).
The default value for this parameter is 10^-3.

[--signal]

This inter value describes which signal is to be processed:

• 0: Vertex positions
• 1: Vertex normals (will be assigned if none are give)
• 2: Vertex colors
• 3: Vertex normals used to fit the geometry.

The default value for this parameter is 0.

[--verbose]

If this flag is enabled, the code will output processing information.

• Top row: Isotropic sharpening:

       ShapeGradientDomain --in armadillo.ply --out armadillo.sharp.ply --gScale 2 --gWeight <gradient weight> 

• Middle row: Isotropic smoothing:

       ShapeGradientDomain --in armadillo.ply --out armadillo.smooth.ply --gScale 0 --gWeight <gradient weight> 

• Bottom row: Anisotropic smoothing:

       ShapeGradientDomain --in armadillo.ply --out armadillo.smooth.ply --gScale 0 --gWeight <gradient weight> --kWeight 0.02 --nIters 1