When designing molecular environments with SAMSON, users often add light sources to better visualize molecular structures. However, it’s not uncommon for modelers to wonder: why is my light not showing up? If you’ve experienced this, you’re not alone. This blog post explores the key visibility attributes of lights in SAMSON and helps you understand how to ensure your lights are truly visible in your scene.
Understanding Light Visibility in SAMSON
Lights in SAMSON are treated as nodes, which means they inherit several general attributes from the node attribute space. Specifically, light visibility depends on the correct combination of three attributes:
visible (v)hidden (h)visibilityFlag (vf)
If any of these are not properly set, your light may not appear, making it hard to detect and fix lighting issues in your model.
Visibility Checklist
Here are the three key attributes that affect whether a light is visible:
li.v: The visible attribute
This is a direct flag indicating whether the light is currently visible in the scene. It must be set to true.
li.h: The hidden attribute
If this is set to true, the light will be hidden—even if its visible flag is true. Use not li.h to find lights that are not hidden.
li.vf: The visibilityFlag
This flag is often set by the application to indicate whether the node (light) can be considered visible. If it’s set to false, the light may be suppressed from rendering.
How to Select Only the Lights That Are Truly Visible
You can use the Node Specification Language (NSL) in SAMSON to efficiently select or highlight lights based on their visibility states. To find lights that are effectively visible, combine the three checks:
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li.v and not li.h and li.vf |
This command selects all lights that:
- Are marked as visible with
li.v - Are not explicitly hidden with
li.h - Have their visibility flag
li.vfenabled
Running this query can help you quickly troubleshoot visibility issues, especially in complex environments with multiple lights and overlays.
Bonus: Turn Lights Off Quickly
If you want to turn off all visible lights temporarily for clarity, you can invert the logic. Use:
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li.v |
to select all visibly active lights and then disable them in SAMSON’s interface. Or use:
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not li.v |
to find those already off.
Conclusion
Lights are crucial for molecular visualization, and understanding the interplay of visible, hidden, and visibilityFlag can help you avoid the confusion of invisible lights. These quick checks and commands can save time and make sure your molecular scenes look exactly as you intend.
To learn more, visit the full documentation page here.
SAMSON and all SAMSON Extensions are free for non-commercial use. You can download SAMSON at https://www.samson-connect.net.