Python Calculator

The python calculator is a programmable calculator that provides common mathematical operations and apply them on the point data, cell data or the input datasets directly. It is similar to the python programmable filter and utilizes its functionality to build python scripts for execution. For efficiency, the actual computation is delegated either to corresponding VTK filters or to the numpy library.

Below is a list of mathematical functions currently supported by this python calculator. Notice that these functions are also available in the python programmable filter.

<source lang="cpp"> [Name ] [Supported Operand Types] [Number of Operands] [Data Association] abs scalar vector tensor 1 point or cell cross vector 2 point or cell curl vector 1 point or cell det tensor 1 point or cell determinant tensor 1 point or cell dot scalar vector 2 point or cell eigenvalue tensor 1 point or cell eigenvector tensor 1 point or cell global_mean scalar vector tensor 1 point or cell global_max scalar vector tensor 1 point or cell global_min scalar vector tensor 1 point or cell gradient scalar vector 1 point or cell inverse tensor 1 point or cell laplacian scalar 1 point or cell ln scalar vector tensor 1 point or cell log(==ln) scalar vector tensor 1 point or cell log10 scalar vector tensor 1 point or cell max scalar vector tensor 1 point or cell min scalar vector tensor 1 point or cell mean scalar vector tensor 1 point or cell mag scalar vector 1 point or cell norm scalar vector 1 point or cell strain vector 1 point or cell trace tensor 1 point or cell vorticity vector 1 point or cell

[Name ] [Supported Cell Types] [Data Association] area trig quad cell aspect trig quad tet cell aspect_gamma tet cell diagonal hex cell jacobian quad tet hex cell max_angle trig quad cell min_angle trig quad cell shear quad hex cell skew quad hex cell surface_normal trig cell volume tet hex cell vertex_normal trig point </source>

Comments

The first list gives all the math functions that work with point data or cell data. The general calling signature is function_name(array) for functions taking one operand or function_name(array1, array2) for functions taking two operands. For example, abs(Normals) computes the absolute value for all normals associated with the dataset component-wise. The array association must be given throuth the GUI interface of the python calculator.

The second list gives all the math functions that directly work with a dataset. Most of them work on the cells of a dataset, with only one exception vertex_normal which computes the normal for each point in a dataset. The calling signature of this category is function_name(inputs[0]) where inputs[0] is defined within the calling context by paraview to be your first input dataset.

In the lists, vector means 3D vectors and tensor stands for 3 by 3 matrix. trig is triangle, quad is quadrilateral, tet is tetrahedron and hex is hexahedron.

Examples

Compute area for each cell

   area(inputs[0]) and array association set to Cell Data

Compute vector length for each point

   sqrt(dot(BrownianVectors,BrownianVectors)) or equivalently mag(BrownianVectors) 

where BrownianVectors is an array of 3D vectors that are associated with each point in the dataset. Array association set to Point Data.

A more complex example

   max(abs(trace(inverse(gradient(Normals)))))

Normals is an array of 3D vectors that are associated to each point in the dataset. The expression first computes for each component of the normal vector its gradient, therefore effectively generates a tensor and then it takes the inverse of the generated matrix and then sum everything on the diagonal of the inverse matrix and then computes the absolute value of the sum and then looks for the maximum of all the absolute values.