Quadric Surfaces

This plugin is not capable of transforming a generic mesh surface into quadric geometries. Instead, it provides a set of predefined objects for constructing the geometry. If more flexibility is needed, the user can use the Triangular Meshes geometry format. These objects are listed in a submenu named Quadric in the Add menu, as shown in the following image:

Note that only the objects listed in the Quadric submenu can be exported as quadric surfaces. Other types of objects will be ignored by the quadrics exporter. To determine if an object is quadric-compatible, the user can check if the Body Properties panel has a properties block named Quadric Properties:

Transformation Handling for Export

The Quadric exporter directly uses Blender's object properties and transformations (location, rotation and bounding box size) to define geometry parameters in the PenRed/PENELOPE quadric format. Therefore, vertex modifications done in edit mode will produce unexpected behaviours in the exported quadric geometry.

⚠️ Critical Warning:
Applying object transformations in Blender will result in exported geometry that doesn't match the viewport representation.

Best Practices

✅ Do:

• Keep all transformations unapplied before exporting
• Modify objects using:
  • Object Mode transforms
  • Transform properties panel (N panel)
  • Native transformation tools

❌ Don't:

• Use Ctrl+A > "Apply" operations:
  • "Apply Rotation & Scale"
  • "Apply Location"
  • "Apply All Transforms"

Consequences of Applying Transforms

Action	Export Result	Viewport Appearance
Keep transforms	Correct export	Matches export
Apply transforms	Incorrect export	Still looks correct

Quadric Parameters

Regardless of the quadric object type, the following parameters must be specified to define the object in the geometry:

• Material Index
  Sets the material index filling this body. Note that the first defined material corresponds to material index 1, as index 0 is reserved for void regions.

• Module
  If enabled, the geometry package will assume this object is a module. This means none of its surfaces are crossed by other bodies or module surfaces. Therefore, all descendant bodies and modules must be completely included inside the module volume. If used, this option speeds up the particle tracking calculations, but the user must ensure the requirements are fulfilled.

Additionally, the following object types require additional parameters:

• Cone: The top and bottom radius must be specified.
• Trapezoid: The (dx,dy) dimensions for both, top and bottom faces, must be specified.
• Tube: The radius for both outer and inner cylinders, must be specified.

Cutting Planes

Optionally, any quadric object can be cut using planes to modify its shape. These cuts are defined as boolean operations, which can be added or removed from the object using the Quadric Properties panel. This ensures the structure is created as intended or removed entirely.

When a cutting plane is created, both a boolean modifier and the corresponding plane are generated. You can select these planes by clicking their names in the Cutting Planes panel:

Once selected, the cutting plane becomes visible in the 3D viewport and can be moved or rotated to achieve the desired shape. Note that cutting planes are only visible when selected:

To remove a specific cutting plane, click the trash icon next to its name in the panel.