MayaVi supports data picking. While visualizing some data press the p or P key to pick the data point above the current mouse position. This will pop up a new window where the picked values will be displayed. The window also has a few controls that let you configure the type of picking you wish to perform. Please note that the picker will pick data on the actors that you have visualized on screen. It will attempt to find the nearest actor and pick the data on that. The picked point will be highlighted using an axes. The picker supports picking the following:
This option is the default and lets you pick the nearest point in the data. You could use this if you have data specified as point data. Note that when you pick using this option the picked location may not be exactly where you placed the mouse. The location will snap to the nearest available point. By changing the tolerance presented in the GUI you can control how near the point should be to the exact picked position.
This option lets you pick the nearest cell in the data. You could use this if you have data specified as cell data. By changing the tolerance you can control how closely the picker finds the nearest cell.
This option lets you pick an arbitrary point in space that is not tied to the nearest cell or point. The motion of this picker is much smoother than the point or cell picker. However, the point that you pick will not be exactly at a point in the actual data. The results will therefore be interpolated using a probe filter.