Blueprint reader can mess up fields for point meshes.

[BradWhitlock]

Describe the bug

I noticed in ExplicitCoordsToVTKPoints that there is code to check the topology to make a vtkPoints object that contains only the used points for point meshes. Vertex-associated fields will have the number of values that the coordset has. This operation reduces the number of points in the VTK dataset, making it no longer match any vertex-associated fields. Later when a vertex-associated field is retrieved, VisIt just copies it into a VTK data array and serves it up. The field has the wrong number of values for the mesh.

Either:
a) Remove this behavior when constructing the points (add them all like other unstructured topos)
b) Or, use the connectivity to pull out the relevant field values when making a field

Option a is probably easiest/best.

To Reproduce

This YAML file makes 8 points but only selects 4 of them via connectivity. When making a PC plot of "wrong", it shows all 10's instead of the negative values that should be shown, according to the connectivity.

Take this YAML file and convert it to blueprint.

coordsets: 
  coords: 
    type: "explicit"
    values: 
      x: [0., 1., 0., 1., 0., 1., 0., 1.]
      y: [0., 0., 1., 1., 0., 0., 1., 1.]
      z: [0., 0., 0., 0., 1., 1., 1., 1.]
topologies: 
  mesh: 
    coordset: "coords"
    type: "unstructured"
    elements: 
      shape: "point"
      connectivity: [4, 5, 6, 7]
      sizes: [1, 1, 1, 1]
      offsets: [0, 1, 2, 3]
fields: 
  zonal: 
    topology: "mesh"
    association: "element"
    values: [10., 10., 10., 10.]
  wrong: 
    topology: "mesh"
    association: "vertex"
    values: [10., 10., 10., 10., -2., -3., -4., -5.]

conduit_relay_io_convert pointmesh.yaml pointmesh --write-protocol blueprint

Expected behavior

Plot the data, get 4 points, and show the negative values for a PC plot of "wrong".

Desktop

/usr/gapps/visit on RZ.

[JustinPrivitera]

Others are welcome to work on this, but I am happy to take it if no one else gets to it. Hence my assignment.