Load a STEP file

Use the pychrono.cascade module to load a STEP file saved from a CAD. We provide the .step file in the data/ directory for this example.

Uses PyChrono.

Learn how to:

• load a STEP file, saved from a 3D CAD.
• fetch parts from the STEP document and conver into Chrono bodies.

#------------------------------------------------------------------------------
# Name:        pychrono example
# Purpose:
#
# Author:      Alessandro Tasora
#
# Created:     1/01/2019
# Copyright:   (c) ProjectChrono 2019
#------------------------------------------------------------------------------
 
import pychrono.core as chrono
import pychrono.irrlicht as chronoirr
import pychrono.cascade as cascade
from OCC.Core  import TopoDS
 
 
    
    
print ("Example: Load a STEP file, generated by a CAD")
 
# The path to the Chrono data directory containing various assets (meshes, textures, data files)
# is automatically set, relative to the default location of this demo.
# If running from a different directory, you must change the path to the data directory with: 
#chrono.SetChronoDataPath('path/to/data')
 
 
# ---------------------------------------------------------------------
#
#  Create the simulation system and add items
#
 
mysystem      = chrono.ChSystemNSC()
 
# Load a STEP file, containing a mechanism. The demo STEP file has been
# created using a 3D CAD (in this case, SolidEdge v.18).
#
 
# Create the ChCascadeDoc, a container that loads the STEP model
# and manages its subassembles
mydoc = cascade.ChCascadeDoc()
 
 
# load the STEP model using this command:
load_ok = mydoc.Load_STEP(chrono.GetChronoDataFile('cascade/assembly.stp'))  # or specify abs.path: ("C:\\data\\cascade\\assembly.stp");
 
# print the contained shapes
#mydoc.Dump(chrono.GetLog())
 
 
# In most CADs the Y axis is horizontal, but we want it vertical.
# So define a root transformation for rotating all the imported objects.
rotation1 = chrono.ChQuaternionD()
rotation1.Q_from_AngAxis(-chrono.CH_C_PI / 2, chrono.ChVectorD(1, 0, 0))  # 1: rotate 90° on X axis
rotation2 = chrono.ChQuaternionD()
rotation2.Q_from_AngAxis(chrono.CH_C_PI, chrono.ChVectorD(0, 1, 0))  # 2: rotate 180° on vertical Y axis
tot_rotation = chrono.ChQuaternionD()
tot_rotation = rotation2 % rotation1     # rotate on 1 then on 2, using quaternion product
root_frame = chrono.ChFrameMovingD(chrono.ChVectorD(0, 0, 0), tot_rotation)
 
# Retrieve some sub shapes from the loaded model, using
# the GetNamedShape() function, that can use path/subpath/subsubpath/part
# syntax and * or ? wildcards, etc.
 
mrigidBody1 = 0
mrigidBody2 = 0
 
if load_ok: 
    
    shape1 = TopoDS.TopoDS_Shape()
    if (mydoc.GetNamedShape(shape1, "Assem1/body1")):
        
        mbody1 = cascade.ChBodyEasyCascade(shape1, 1000) # density
        
        mysystem.Add(mbody1)
        
        mbody1.SetBodyFixed(True) 
        
        # Move the body as for global displacement/rotation (also mbody1 %= root_frame; )
        mbody1.ConcatenatePreTransformation(root_frame);
        
        mrigidBody1= mbody1;
        
    else:
        print("Warning. Desired object not found in document \n")
 
    shape2 = TopoDS.TopoDS_Shape()
    if (mydoc.GetNamedShape(shape2, "Assem1/body2")): 
        
        mbody2 = cascade.ChBodyEasyCascade(shape2, 1000) # density
        
        mysystem.Add(mbody2)
        
        # Move the body as for global displacement/rotation  (also mbody2 %= root_frame; )
        mbody2.ConcatenatePreTransformation(root_frame);
 
        mrigidBody2= mbody2;
        
    else:
        print("Warning. Desired object not found in document \n")
 
else:
    print("Warning. Desired STEP file could not be opened/parsed \n")
 
# Create a revolute joint between the two parts
# as in a pendulum. We assume we already know in advance
# the aboslute position of the joint (ex. we used measuring tools in the 3D CAD)
 
measured_joint_pos_mm = chrono.ChVectorD(0, 48, 120);
 
scale = 1. / 1000.  # because we use meters instead of mm
 
joint_pos = chrono.ChVectorD(root_frame.TransformPointLocalToParent(measured_joint_pos_mm * scale)) 
                             # transform because we rotated everything
 
if (mrigidBody1 and mrigidBody2):
    my_link = chrono.ChLinkLockRevolute()
    my_link.Initialize(mrigidBody1, mrigidBody2, chrono.ChCoordsysD(joint_pos));
    mysystem.Add(my_link);
 
 
# Create a large cube as a floor.
 
mfloor = chrono.ChBodyEasyBox(1, 0.2, 1, 1000)
mfloor.SetPos(chrono.ChVectorD(0,-0.3,0))
mfloor.SetBodyFixed(True)
mysystem.Add(mfloor)
 
mcolor = chrono.ChColorAsset(0.3, 0.3, 0.8)
mfloor.AddAsset(mcolor)
 
 
 
# ---------------------------------------------------------------------
#
#  Create an Irrlicht application to visualize the system
#
 
myapplication = chronoirr.ChIrrApp(mysystem, 'Test', chronoirr.dimension2du(1024,768))
 
myapplication.AddTypicalSky()
myapplication.AddTypicalLogo(chrono.GetChronoDataFile('logo_pychrono_alpha.png'))
myapplication.AddTypicalCamera(chronoirr.vector3df(0.2,0.2,-0.2))
myapplication.AddTypicalLights()
 
            # ==IMPORTANT!== Use this function for adding a ChIrrNodeAsset to all items
            # in the system. These ChIrrNodeAsset assets are 'proxies' to the Irrlicht meshes.
            # If you need a finer control on which item really needs a visualization proxy in
            # Irrlicht, just use application.AssetBind(myitem); on a per-item basis.
 
myapplication.AssetBindAll();
 
            # ==IMPORTANT!== Use this function for 'converting' into Irrlicht meshes the assets
            # that you added to the bodies into 3D shapes, they can be visualized by Irrlicht!
 
myapplication.AssetUpdateAll();
 
 
# ---------------------------------------------------------------------
#
#  Run the simulation
#
 
 
myapplication.SetTimestep(0.01)
 
 
while(myapplication.GetDevice().run()):
    myapplication.BeginScene()
    myapplication.DrawAll()
    myapplication.DoStep()
    myapplication.EndScene()