When you’re managing complex molecular systems in SAMSON, ensuring that your scene renders exactly what you expect is critical—especially when working with lighting. However, debugging visibility and selection issues for light sources can be frustrating, especially in scenes with multiple light nodes and nested structures. If you’ve ever found yourself wondering why a light doesn’t appear to influence your scene or if it’s being incorrectly toggled, this article is for you.
What’s affecting your light nodes?
In SAMSON, lights are represented as nodes, just like atoms, molecules, or groups. This means they come with a set of attributes that you can query or modify using the Node Specification Language (NSL). These attributes can be extremely helpful when creating scripts, building complex filters, or debugging visibility issues.
The light attribute space (short name: li) in NSL offers a structured way to access and filter light nodes based on key attributes. These include:
- visible (
li.v): Whether the light is visible in the scene. - hidden (
li.h): Whether the light is explicitly hidden by the user. - visibilityFlag (
li.vf): Whether the light is flagged to be visible in the current SAMSON view context. - selectionFlag (
li.sf): Whether the node is internally flagged as selected. - name (
li.n): The user-defined or default name of the light node.
Each of these plays a role, and only when they’re all set appropriately will your light node behave as expected.
Using NSL to diagnose visibility issues
Imagine you’ve added a light to your scene named MyLight, but it’s not affecting the illumination. Instead of toggling random visibility switches or hoping for the best, use NSL queries directly in the Search box or scripts. For example:
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li.n "MyLight" and not li.v |
This will help you find if MyLight is present but currently not visible. If it’s not visible, maybe it’s marked hidden or its visibilityFlag is set to false.
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li.vf false |
That query tells you which lights are flagged as not visible in the current view. Refine further by combining expressions:
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li.n "L*" and li.vf |
This finds all light nodes whose names start with “L” and are flagged as visible.
Shortcuts for better scripting
If you’re scripting repetitive tasks or building visual analysis pipelines, using short names can speed things up. For instance, instead of typing li.visible, simply use li.v. Here’s a quick mapping:
v= visiblevf= visibilityFlagsf= selectionFlagh= hiddenn= name
Remember: some attributes like selected do not have a short name for lights. Only li.selected is valid.
Why this matters
In a molecular modeling workflow, especially for presentations or simulations involving lighting effects (say, when showing the topology of a protein or rendering ligand docking results), having fine-grained control over light node visibility is essential. These NSL patterns help you cleanly manage which lights are active, visible, and selected, making sure no hidden lights are unintentionally affecting your scene. Plus, if you’re collaborating or sharing your SAMSON files, clean visibility logic ensures others see your data just as you intended.
To see all the options and detailed examples, you can explore the official documentation here:
https://documentation.samson-connect.net/users/latest/nsl/light/
SAMSON and all SAMSON Extensions are free for non-commercial use. You can get SAMSON here.