C3D Interactive 3D Viewer

C3D provides an interactive 3D molecule viewer for Jupyter and Marimo notebooks, powered by 3Dmol.js. It generates self-contained HTML with no external network requests, making it suitable for offline use and secure environments.

The viewer includes a built-in GUI with a sidebar for toggling molecule visibility, a menubar with view controls, and a terminal for executing 3Dmol.js commands interactively.

Quick Start

from cnotebook.c3d import C3D
from openeye import oechem

mol = oechem.OEMol()
oechem.OESmilesToMol(mol, "c1ccccc1 benzene")  # SMILES with optional title

viewer = C3D().add_molecule(mol)
viewer.display()

You’ll see the following warning Molecule 'benzene' lacks 3D coordinates; generating with OEOmega." This is normal, since the molecule converted from SMILES contains no 3D coordinates but you’re trying to display it in 3D.

C3D is also available at the top level when its dependencies are present:

import cnotebook

# ... code that loads a molecule ...
viewer = cnotebook.C3D().add_molecule(mol)
viewer.display()

Adding Molecules

Use add_molecule to add OpenEye molecules. If the molecule lacks 3D coordinates, CNotebook will automatically generate them using Omega.

# Read two molecules from the example notebooks
mol1 = oechem.OEGraphMol()
mol2 = oechem.OEGraphMol()

with oechem.oemolistream("examples/assets/5FQD_ligand.sdf") as ifs:
    oechem.OEReadMolecule(ifs, mol1)

with oechem.oemolistream("examples/assets/6XK9_ligand.sdf") as ifs:
    oechem.OEReadMolecule(ifs, mol2)

# View them both as sticks
viewer = (
    C3D()
    .add_molecule(mol1)
    .add_molecule(mol2)
    .add_style("stick")
)
viewer.display()

Note that adding two molecules automatically displays the sidebar. The names of each entry on the sidebar are taken from the molecule titles. If you want to custom names, use the name parameter on add_molecule and provide your own name.

Adding Design Units

Design units (protein-ligand complexes) are added with add_design_unit. The full complex is extracted and written as PDB format for 3Dmol.js.

from openeye import oechem
from cnotebook.c3d import C3D

du = oechem.OEDesignUnit()
oechem.OEReadDesignUnit("examples/assets/spruce_9Q03_ABC__DU__A1CM7_C-502.oedu", du)

viewer = (
    C3D()
    .add_design_unit(du, name="complex")
    .set_preset("sites")
    .orient("resi 502")
)
viewer.display()

Note that orient will orient the molecule based on it’s principal components and zoom to it. It does not guarantee that no residues will be in the way.

Disabled Molecules

Molecules and design units can be loaded in a disabled state using the disabled parameter. Disabled entries are not displayed when the viewer starts, but can be toggled on via the sidebar.

# ... load two molecules 'mol' and 'ref'
viewer = (
    C3D()
    .add_molecule(mol, name="active")
    .add_molecule(ref, name="reference", disabled=True)
)
viewer.display()

View Presets

Presets are compound styles defined in the GUI that combine multiple representations into a common visualization. When a preset is set, it replaces any styles added via add_style.

Available presets:

  • "simple" – Element-coloured cartoon with per-chain carbons and sticks for ligands.

  • "sites" – Like simple, plus stick representation for residues within 5 angstroms of ligands.

  • "ball-and-stick" – Ball-and-stick for ligands only.

viewer = (
    C3D()
    .add_design_unit(du, name="complex")
    .set_preset("sites")
)
viewer.display()

Custom Styles

For finer control, add individual 3Dmol.js styles with add_style:

viewer = (
    C3D()
    .add_molecule(mol)
    .add_style({"chain": "A"}, "cartoon", color="blue")
    .add_style({}, "stick")
)
viewer.display()

Style presets: cartoon, stick, sphere, line, cross, surface.

You can also pass a raw 3Dmol.js style dict for full control:

viewer.add_style({"resi": 42}, {"cartoon": {"color": "spectrum"}})

Zoom Targets

The zoom_to method sets the initial zoom target after loading.

  • String selection – Parsed by the GUI’s selection engine:

    viewer.zoom_to("resn 502")
viewer.zoom_to("chain A")

  • Dict selection – Passed directly to 3Dmol.js:

    viewer.zoom_to({"chain": "A"})

  • None – Fit all molecules in view (the default).

UI Configuration

Control which GUI panels are visible:

viewer = (
    C3D()
    .add_molecule(mol)
    .set_ui(sidebar=True, menubar=True, terminal=True)
)
viewer.display()

Background Color

Set the viewer background colour with any CSS colour string:

viewer.set_background("#ffffff")
viewer.set_background("white")

Builder API

All configuration methods return self, enabling fluent method chaining:

viewer = (
    C3D(width=1024, height=768)
    .add_design_unit(du, name="protein")
    .add_molecule(ligand, name="ligand")
    .add_style({"chain": "A"}, "cartoon", color="blue")
    .set_preset("sites")
    .set_ui(sidebar=True, menubar=True, terminal=False)
    .set_background("#ffffff")
    .zoom_to("resn 502")
)
viewer.display()

HTML Export

Use to_html() to get the raw HTML string for embedding or saving:

html = viewer.to_html()
with open("viewer.html", "w") as f:
    f.write(html)

The generated HTML is fully self-contained with all JavaScript and CSS inlined.