Figura Primer
Figura is build on top of pythonocc-core which is a python wrapper around Open Cascade technology. Briefly, Open Cascade is modelling engine using boundary representation with very rich API and coming with a lot of capabilities. This can be quite overwhelming for a new-comer and this is one of the reasons figura was created.
Figura tries to offer intuitive API to allow users to create their paramerical models easily.
It provides simple modeling primitives like Point, Line, Circle, Box, Cylinder, etc.
that can be used to build complex geometries.
The final models can be exported to industry standard file formats like STEP. These files can then be used for further processing.
Basic Concepts
The basic concept is based on object-oriented approach to models.
Core modeling entities can be combined into higher-level entities.
Using the python language, composition and inheritance is available to create more complicated models.
Object-Oriented Models
Since the modeling entities in figura are python objects, the user doesn’t deal with ID-based models. Compare the following two approaches:
pt1 = Point(0, 0, 0)
pt2 = Point(1, 0, 0)
line = Line(pt1, pt2)
create vertex 0 0 0
create vertex 0 0 1
create curve vertex 1 2
In the Cubit example, there is no notion that the command create vertex 0 0 0 created a vertex
with ID 1 that can be passed into the create curve command.
In figura, since all entities are objects, they are referred to via their variable names.
This leads to a great robustness of the script that produces the final model.
Putting Entities Together
The model can be build from bottom up. Starting from points that are connected into edges, that are used to create wires, which are then used to build face which can then be used to build solid shapes.
pt1 = Point(0, 0, 0)
pt2 = Point(1, 0, 0)
pt3 = Point(0, 1, 0)
triangle = Face(Polygon([pt1, pt2, pt3]).wire())
vec = Vector(0, 0, 1)
solid = triangle.extrude(vec)
Using Modeling Primitives
Modeling primitives like Cylinder, Box, Sphere, etc. are available to create solid objects quickly.
Those can then be combined together to create more complicated models.
origin = Point(0, 0, 0)
z_vec = Direction(0, 0, 1)
axis = Axis2(origin, z_vec)
cyl = Cylinder(axis, 0.5, 2)
sph_ctr = Point(0, 0, 2)
sph = Sphere(sph_ctr, 0.5)
solid = cyl.fuse(sph)
Running figura
You can create a standalone python file that can be executed in the usual manner:
example.py:
from figura import *
<figura objects>
export("prim.step", [<objects to export>])
$ python example.py
example.figura:
<figura objects>
export = [<objects to export>]
$ figura example.figura example.step