Editing CAD meshes

In OghmaNano, every 3D object has both a simple bounding shape and, optionally, a more detailed CAD mesh. By default, complex CAD meshes are disabled and each object is drawn using a generic box defined by its size in the Object editor. This section explains how to enable complex meshes and how to use the Mesh editor to configure different primitive shapes such as pyramids, tubes, and hollow tubes.

User right-clicking an object in the 3D view and choosing Edit object. — Right-click an object in the 3D scene and select **Edit object** to open the Object editor.

OghmaNano Object editor window showing basic object properties and Complex meshes disabled. — The *Object editor*, where you can configure the object's position, size, colour, material and shape. By default the object shape is a simple box and complex meshes are disabled.

To edit an object, right-click it in the 3D view and choose Edit object, as shown in ??. This opens the Object editor window (??). Here, the xyz size fields (dx, dy, and dz) define the size of the object's default box-shaped representation. You can also change the object's position, rotation, colour, and the material it is made from.

At the bottom of the Object editor under Object shape, the text Complex meshes disabled indicates that no detailed CAD mesh is currently being used for this object. In this mode, the object is always drawn as a simple box, regardless of what optical material or other properties you choose.

Enabling the Mesh editor

To enable complex CAD meshes, click the Edit button (with three dots) next to Object shape in the Object editor. This opens the Mesh editor. When you first open it for an object, the mesh system is disabled, as illustrated in ??.

Mesh editor window showing complex meshes disabled. — The *Mesh editor* when complex meshes are disabled. Click the **Disabled** button to enable mesh editing for this object.

Click the Disabled button in the toolbar of the Mesh editor to turn complex meshes on. Once enabled, the editor switches to its default primitive shape, which is a pyramid. The configuration controls and the resulting mesh are discussed in more detail in the following sections, starting with the pyramid in ??.

Pyramid

When complex meshes are first enabled for an object, the default primitive is a pyramid. The Mesh editor displays a toolbar of available primitives (box, prism, sphere, tube, hollow tube, pyramid, etc.) and a configuration panel for the active shape. For the pyramid, you can set its base radius, height, and number of sides. The pyramid mesh then replaces the simple box for that object in the 3D view.

Wireframe pyramid mesh rendered in the 3D scene. — The resulting pyramid mesh in the 3D scene. The red wireframe shows the triangulated CAD mesh, replacing the simple box shape.

Adjusting the pyramid parameters in ?? immediately updates the mesh shown in the main 3D window (??). This makes it easy to fine-tune the overall dimensions before combining the object with other optics in your simulation.

Tube

The Tube primitive creates a solid cylinder. This is useful for modelling rods, pillars, or waveguides. In the configuration panel you can set the overall radius, height, and the discretisation of the mesh via the number of rings and segments.

Wireframe cylinder mesh rendered in the 3D scene. — The resulting solid tube mesh in the 3D view. A finer choice of rings and segments produces a smoother-looking cylinder at the cost of more triangles.

As with the pyramid, any changes you make in the tube configuration window (??) are reflected immediately in the rendered mesh (??). Increasing the number of rings and segments increases mesh density, which can improve geometric fidelity but may also increase ray-tracing time.

Hollow tube

The Hollow tube primitive generates a cylindrical shell, with a user-defined inner and outer radius. This is useful for modelling pipes, hollow waveguides, or annular support structures. In addition to radius and height, you can set the number of rings and segments to control the triangulation of the mesh.

Wireframe hollow cylinder mesh rendered in the 3D scene. — The hollow tube mesh in the 3D scene. The red wireframe outlines both the inner and outer cylindrical surfaces.

By adjusting the inner and outer radii in ??, you can move smoothly between a thin-walled shell and a nearly solid cylinder. As before, the mesh resolution is governed by the number of rings along the axis and the number of angular segments around the circumference (??).

Sphere

The Sphere primitive creates a triangulated spherical surface. In the configuration panel you can set the sphere Radius, along with the number of Rings (latitudinal divisions) and Segments (longitudinal divisions). Together these parameters control how finely the sphere is tessellated and therefore how smooth it appears in the 3D view.

Wireframe sphere mesh rendered in the 3D scene. — The resulting spherical mesh in the 3D view. Increasing the rings and segments makes the surface appear smoother at the expense of more triangles.

For many optical applications a moderate number of rings and segments is sufficient; increasing these values beyond what is visually smooth will only increase simulation time without improving accuracy. Use ?? and ?? as a guide when choosing suitable values.

Prism

The Prism primitive is designed for creating simple wedge-shaped or peaked structures. In the configuration panel you specify the overall xyz size of the prism (its dx, dy, and dz dimensions). The Peak in center option controls whether the peak of the prism is in the middle of the footprint or offset to one side.

Wireframe prism mesh rendered in the 3D scene. — The prism mesh in the 3D scene. The triangulated faces meet at the peak defined in the configuration window.

Prisms are useful for building up more complex optical components, such as light-redirecting structures or simple beam deflectors. The relationship between the dx, dy, and dz values in ?? and the resulting geometry shown in ?? is direct, making it straightforward to design and tweak these shapes.

Box

The Box primitive provides an explicit mesh-based version of the simple rectangular box used when complex meshes are disabled. You can specify the size of the box in the xyz size fields (dx, dy, dz). In most cases there is no practical advantage to using a box mesh instead of leaving the object as the default box shape, but the option is provided for completeness and for situations where you want all objects to use the mesh system consistently.

Mesh editor window showing configuration options for a box. — Configuration options for a **Box**: the `x`, `y`, and `z` dimensions match those used for the default object box.

Wireframe box mesh rendered in the 3D scene. — The box mesh in the 3D scene. The triangulated faces reproduce the same geometry as the default rectangular object.

If you only need a simple rectangular object, you can normally leave complex meshes disabled and rely on the default box. However, the mesh-based box in ?? and ?? can be useful when you want consistent mesh-level control (for example, when exporting geometry or when combining with other mesh primitives).

Aperture

The Aperture primitive is intended for modelling optical stops and diaphragms. It creates a flat plate with a polygonal opening in the centre. In the configuration panel you specify the outer diameter d0, the inner diameter d1 (the clear aperture), and the number of Blades, which sets the number of sides of the polygonal opening.

Wireframe aperture mesh rendered in the 3D scene, showing the polygonal opening. — The aperture mesh in the 3D scene. The central polygonal opening defines the region through which light can pass.

In a typical optical model, the material of the aperture plate is set to an absorbing or metallic medium so that only light passing through the opening contributes to the simulation. By adjusting d0, d1, and the number of blades in ??, you can quickly prototype different stop sizes and shapes and immediately see the resulting geometry shown in ??.

Lens

The Lens primitive in the Mesh Editor allows you to construct fully triangulated optical lenses. Lenses may be round or square, and each surface can take one of several shapes: plano (flat), spherical, parabolic, ellipsoid, hyperbolic, or aspheric. These options enable flexible modelling of optical elements for ray-tracing.

Each lens has two surfaces—Surface 0 and Surface 1—and each surface can be configured independently. Parameters include:

Surface r — Radius of curvature (positive or negative depending on whether the surface is convex or concave).
Surface k — Conic constant for non-spherical surfaces.
Surface A4, A6, … — Higher-order aspheric coefficients.
ct — Centre thickness of the lens body.
Diameter — Physical diameter of the lens.
Hole diameter — Size of an optional central hole.

The Lens Editor is powerful, but in most optical workflows lenses are more easily manipulated using the S-plane editor, described later. The Mesh Editor is mainly useful when you need explicit triangulated lens geometry for export or for visual debugging.

Lens editor configuration window showing aspheric surface parameters. — The **Lens configuration** panel. Both surfaces may be set to plano, spherical, parabolic, ellipsoid, hyperbolic, or aspheric. Parameters such as r, k, A4, and A6 define the curvature and higher-order behaviour of each surface.

Concave lens mesh shown in the 3D scene. — A **concave lens** produced using the Mesh Editor. The triangulated surface follows the curvature specified in ??.

Lens with central hole rendered in the 3D scene. — A lens with a **central hole**. The hole size is controlled by the **Hole diameter** field. Such lenses are used in specialised optical layouts where central obscurations must be modelled.

Convex lens mesh shown in the 3D scene. — A **convex lens** with both surfaces set to curved profiles. The triangulated form is suitable for detailed optical simulations where physical shape must be modelled explicitly.

Together, the configuration examples in ??, ??, ??, and ?? demonstrate how the Lens Editor can construct a wide range of optical elements.

Shape database

The Shape Database option provides access to a library of pre-defined CAD meshes stored in OghmaNano’s own format. These shapes are not generated on the fly by the Mesh Editor; instead they are loaded directly from the internal database and can be reused across multiple simulations.

In addition to standard library shapes, you can also import flat images—such as AFM height maps—into the Shape Database and convert them into 3D objects. This makes it a convenient place to keep frequently used geometries together, whether they originate from measurements, external CAD tools, or previous projects.

Mesh editor window showing a shape selected from the internal shape database. — The **Shape Database** panel. A stored CAD mesh (here named `teapot`) is selected from the internal library and scaled using the **xyz size** fields.

Once a shape has been chosen in ??, it behaves like any other mesh primitive: it is attached to the current object and participates fully in the ray-tracing simulation.

Importing CAD files

Instead of first adding shapes to the internal database, it is also possible to attach meshes directly from external CAD files using the CAD File option. This is useful when you already have a model stored on disk and simply want to bring it into an OghmaNano simulation.

At present, the importer supports standard Wavefront OBJ files. Other, non-standard or proprietary formats are not accepted, so if your geometry is stored in a different format it should be exported as a Wavefront OBJ mesh first.

Mesh editor CAD file panel showing the selected OBJ file and scaling controls. — The **CAD File** panel. Use the file selector to choose a Wavefront OBJ file and adjust its **xyz size** to set the physical scale of the imported mesh.

Imported CAD teapot mesh rendered in the 3D scene. — An imported CAD mesh (a teapot) rendered in the 3D scene. The geometry comes directly from an external OBJ file and is then used as a full 3D mesh in the simulation.

The example in ?? and ?? shows how an external CAD model can be brought into OghmaNano and combined with other optical components in the scene.