Avogadro 2
Avogadro libraries provide 3D rendering, visualization, and analysis
...It provides the essential tools for constructing, analyzing, and visualizing molecular structures in 2D and 3D. Designed for extensibility, AvogadroLibs supports plugins for quantum chemistry computations, molecular mechanics, and surface rendering. It interfaces with multiple chemistry formats and data sources, making it a versatile backbone for scientific applications and custom visualization tools.