Finding the mesh you meant: a practical guide to mesh attributes in SAMSON

A crowded molecular scene can make a simple task surprisingly fiddly: you want to inspect a mesh, but several mesh nodes are present, some are hidden, and you are not sure which ones have materials or are selected. The mesh attribute space in SAMSON’s Node Specification Language (NSL) gives you a compact way to describe the mesh nodes you want to find.

The first detail to remember is the attribute-space prefix. Mesh attributes use me, so an expression such as me.h refers to the mesh node’s hidden attribute. The page lists these as inherited node attributes: meshes can be queried using attributes defined for nodes generally, with the mesh prefix specifying the kind of node you are targeting.

Start with the state you need to check

When the problem is visibility, the reference provides both visible (short name v) and hidden (short name h). For example:

• me.v — query the mesh’s visible attribute.
• not me.v — query for the opposite value of visible.
• me.h or not me.h — query the hidden attribute.

These are separate attribute names in the reference, so use the one that matches the question you are asking. If you are diagnosing a display issue, checking the named visibility state directly is clearer than relying on an assumption that two different attributes are interchangeable.

Selection has a similar distinction. Mesh nodes support selected, written as me.selected, and selectionFlag, whose short name is sf and whose examples include me.sf and me.sf false. One important syntax detail: unlike the node attribute reference, selected has no short name for meshes. Use the full form rather than trying me.s.

Check material state without guessing

Two material-related attributes are available: hasMaterial (hm) and ownsMaterial (om). The reference shows examples such as me.hm and me.om. They are distinct attributes, so if you are investigating material assignment or ownership, query the one whose name matches the information you need. The attribute list alone does not define their deeper relationship, so avoid treating one as a substitute for the other.

Use names to narrow down a scene

If you know a mesh’s name, the name attribute (n) accepts strings in quotes. The documentation’s examples are me.n "A" and me.n "L*". This is useful when a scene contains multiple mesh nodes and you want to work from a known label. The examples illustrate the syntax; consult the NSL examples documentation if you need guidance on more complex expressions.

A small, repeatable triage routine

1. Use the me attribute space to target mesh nodes.
2. Check me.n "A" (or the relevant name) when you need to narrow by a label.
3. Inspect visibility with me.v or me.h, and selection with me.selected or me.sf.
4. For material questions, check me.hm and me.om as separate attributes.

This approach turns a vague “where did that mesh go?” moment into a set of specific checks. It also makes expressions easier for a teammate to read: the prefix says what kind of node is being queried, and the attribute says what property you are checking.

For the complete attribute table and details on inherited node attributes, see the SAMSON mesh attributes reference.

Note: SAMSON and all SAMSON Extensions are free for non-commercial use. Get SAMSON.