Implement a correct sample shape object

[Martyn Gigg]

This ticket has 2 parts: (a) a quick resolution to a problem for the SANS group and (b) the more long term fix.

The SANS reduction scales its output using the sample volume and we are not dealing with this in the most generic way. Currently we read fields from the ISIS raw/nexus files that define a basic shape and 3 dimenions: height, width, thickness. These values are stored on the Sample object and used by the SANS script. The problem the SANS group has is that these values are not saved by our SaveNexusProcessed routine.

The first step of the ticket is a temporary fix to make Save/LoadNexusProcessed understand the sample geometry by adding log file entries for the necessary fields:

1. Update SaveNexusProcessed to add the 4 fields; m_geom_id, m_thick, m_height and m_width, as log file fields;
2. Update LoadNexusProcessed to read in these fields from the log file values if they are present.

This needs to be completed fully and committed before moving on.

The longer term and more general fix is to properly define a sample shape object that knows how to calculate its volume. This can then be saved as an XML string and recreated when reloaded. This will require:

1. Modifying ISIS LoadRaw/LoadNexus to create a sample shape object using the CreateSampleShape algorithm;
2. Add the ability of objects to calculate their own volume based upon a triangulated wire mesh that is used to approximate them. At the moment the primitive shapes such as cylinders are defined by a low resolution mesh and we want to be able to be able to specify as a parameter whether we want a low/high resolution triangulation.

[Steve Williams]

(In [4203]) A temporary simple way to save and retrieve sample width, height ... in processed nexus files re #1166

[Steve Williams]

the last check in completed the first section (1. and 2.) of the discription above

[Steve Williams]

Only the first part of this ticket has been completed. The rest is in ticket:1517

[Michael Whitty]

in #5905 - checking in SANS2D interface which updates geometry details as expected, concurs with values held in nxs file when viewed with HDFView

[Stuart Campbell]

This ticket has been transferred to github issue ​2014