I want to spatially model systems of atoms. Atoms have the shape of a sphere and the diameter for all spheres is the same. Spheres cannot deform, they tend to touch each other but overlaps are not allowed.
The GUI shall allow to place spheres in a 3d-environment and render different views. It would be helpful if the program considers that the spheres cannot overlap and arrange the spheres in touch with each other, align them in a line, or bring a sphere in touch with three other spheres on a triangular grid. There are not more than ten spheres to arrange in a scence. Easy placement is possible if I can control which spheres are touching or the program suggests suitable positions.
Esthetics or special artistic effects are not important, it would be sufficient if the color of any sphere can be selected. Setting transparency of a sphere would be optional. Also optional would be the creation of animations of moving spheres.
Examples for programs that are not comfortable
I could use Blender but this is a general-purpose software and not comfortable for my purpose. A code-based renderer like Povray oder OpenSCAD is also quite cumbersome.