Crafting Arc and 3D Models with PythonOCC

In the realm of 3D modeling and CAD (Computer-Aided Design), PythonOCC emerges as a powerful tool, bringing the robust capabilities of Open CASCADE Technology (OCCT) to the Python environment. Let’s dive into a practical example to demonstrate how you can create intricate 3D models using PythonOCC.

Setting Up Your Environment

Before you begin crafting 3D models, you need to set up your environment correctly. This involves specifying the path to your OCC library and ensuring that all necessary modules are imported. Here's how you can do it:

import os
getcwd = os.getcwd()
path = os.path.join(getcwd, "Library\OCC")
os.add_dll_directory(path)

This code snippet sets up the path for the DLLs required by PythonOCC, ensuring smooth execution of the modeling functions.

Importing the Necessary Modules

Next, we import various classes from the PythonOCC library. These classes provide functionalities for creating points, vectors, edges, wires, faces, and more.

from OCC.Core.gp import gp_Ax2, gp_Dir, gp_Circ, gp_Pnt, gp_Vec
from OCC.Core.BRepBuilderAPI import BRepBuilderAPI_MakeEdge, BRepBuilderAPI_MakeWire, BRepBuilderAPI_MakeFace
from OCC.Core.BRepPrimAPI import BRepPrimAPI_MakePrism
from OCC.Display.SimpleGui import init_display

Initiating the 3D Visualization

We initiate a 3D visualization window where our model will be displayed:

display, start_display, add_menu, add_function_to_menu = init_display()

Building the 3D Model

Now, let’s create a simple 3D shape to understand the process:

Define Points and Vectors

We start by defining the start, end, and center points for our shape. We also define the normal vector assuming the shape lies in the XY plane.

start_point = gp_Pnt(1, 0, 0)
end_point = gp_Pnt(0, 1, 0)
center_point = gp_Pnt(0.0, 0.0, 0)
normal_vector = gp_Dir(0, 0, 1)

Creating an Arc

Using these points and the normal vector, we set up a coordinate system and create an arc.

coordinate_system = gp_Ax2(center_point, normal_vector)
radius = center_point.Distance(start_point)
arc = BRepBuilderAPI_MakeEdge(gp_Circ(coordinate_system, radius), start_point, end_point).Edge()

Building the Wire

We construct a wire using the arc and lines connecting the start and end points to the center.

line1 = BRepBuilderAPI_MakeEdge(start_point, center_point).Edge()
line2 = BRepBuilderAPI_MakeEdge(center_point, end_point).Edge()
wire_builder = BRepBuilderAPI_MakeWire()
wire_builder.Add(arc)
wire_builder.Add(line1)
wire_builder.Add(line2)
wire = wire_builder.Wire()

Creating a Face and Prism

We then create a face from this wire and extrude it to form a prism (a 3D shape).

face_builder = BRepBuilderAPI_MakeFace(wire, True)
face_builder.Build()
face = face_builder.Face()
height = 2.0
prism_builder = BRepPrimAPI_MakePrism(face, gp_Vec(0, 0, height))
solid = prism_builder.Shape()

Displaying the Model

Finally, we display the created 3D shape in our visualization window.

display.DisplayShape(solid, update=True)
display.FitAll()
start_display()

Result

Conclusion

Through this example, we’ve seen how PythonOCC can be used to build a simple 3D model. The process involves creating geometric elements, assembling them into more complex shapes, and finally visualizing them. PythonOCC’s integration with Python makes it a versatile tool for anyone looking to explore 3D modeling and CAD in a familiar programming environment.

Remember, this is just the tip of the iceberg. PythonOCC offers extensive functionalities for more complex and intricate designs, making it a valuable asset for engineers, designers, and enthusiasts alike in the field of 3D modeling and CAD.