Make a pass through VTK classes to ensure all methods and arguments are clearly documented.

See bug report 9983 for details.

http://www.vtk.org/Bug/view.php?id=9983

Replace or extend the current observer pattern with signals and slots.

I'd like to be able to build and debug VTK and projects using VTK (Java & C++) in the NetBeans IDE. There's a NetBeans IDE plugin that can interpret Ant projects, but that's an extra step I'd like to avoid.

It would be great if at least the most common filters (stream lines, contour, extract surface...) would take advantage of multiple cores without MPI.

What about to make a web version of vtk with webgl?

Put VTK in a namespace instead of relying on prefixes for avoiding name collisions.

Make enumeration values available from wrapped languages like Python.

When triangulating large volumes, the underlying data type float reaches quickly its limits. Rounding the data to float makes details disappear in case a triangle is far away from the origin of the coordinate system. In case float was choosen in the past for performance reasons, this shouldn't be a reason anymore with modern computers (of course the occupied memory will be twice as much).

A formatter object could allow "pretty printing", serialization, and other customized output. This would extend the current Print() methods.

See http://markmail.org/message/7xgyqly7roj2kofs

Trying to make a real application with vtk that works under windows is nearly imposibble. The problem is that memory allocated by vtk must be consecutive, so it doesn't benefit for virtual memory (swap file memory).
I suggest to create a new class vtkMemory that handle about this. This class stores memory and handle it as it where all consecutive memory, but internally it can be splitted into chunks to allow application to fit into system memory.

To make the vtkScalarBarActor more legible over complex scenery, it would help to have a background with programmable color/opacity like the Box object in the legend of the XYPlot actor.
One implementation difficulty will be in creating a box that encompasses the labels & title which hang outside the area defined by the scalarbar actor's position, width & height. The scalar bar widget would need to be aware of this expanded size so that user's could resize the scalar bar by dragging its new edge.

Store unit information for each *component* of an array. This could be done easily with vtkInformation objects. For example, the vtkDataArray used by a vtkPoints objects might have 3 vtkInformation objects (one for x, y, and z) specifying the units in which each component's values are specified ('km', 'ft.', 'furlong'). A filter could then perform unit conversions for arrays or even do fancy analysis like using Buckingham Pi theory to determine combinations of arrays to examine.

As the current import function of QT Creator for cmake projects cannot handle only-header files properly, it would be helpful if a correct QT project file could be generated by cmake similar to Eclipse.

I've found only TCL examples for VTK via Cuda. Can you give me advice how I can use VTK via nVidia CUDA with Python?

Bryn wrote a couple of nice helper functions for dealing with matrices:
http://www.vtk.org/Wiki/Compute_eigenvalues_and_eigenvectors_of_a_symmetric_matrix

These should be wrapped into a class so the interfaces to many of the vtkMath functions (Jacobi(), for example) do not require the user to use ** variables, but rather can easily interface with a matrix using an (r,c) type notation.