Introduction to Python (3)

Create a postprocessing system based on POVray, using PyChrono.

• create a basic system with two bodies
• create a postprocessor object
• add asset objects to rigid bodies, for visualization
• generate POVray scripts for rendering a 3D animation

#-------------------------------------------------------------------------------
# Name:        pychrono example
# Purpose:
#
# Author:      Alessandro Tasora
#
# Created:     1/01/2019
# Copyright:   (c) ProjectChrono 2019
#
#
# This file shows how to use POV ray for postprocessing, thanks to the
# utility functions in the unit_POSTPROCESS of Chrono::Engine.
#
#-------------------------------------------------------------------------------
 
print ("Third tutorial: use the postprocess module.");
 
 
# Load the Chrono::Engine core module and the postprocessing module!
import pychrono as chrono
import pychrono.postprocess as postprocess
 
# We will create two directories for saving some files, we need this:
import os
 
 
# Create a physical system,
my_system = chrono.ChSystemNSC()
my_systemB = my_system
 
# Create a body
body_1= chrono.ChBodyAuxRef()
my_system.Add(body_1)
 
# Attach a visualization asset to the body (ex.: a sphere)
myasset = chrono.ChSphereShape()
myasset.GetSphereGeometry().rad =0.2
body_1.GetAssets().push_back(myasset)
 
# Assets can be shared, ex. to save memory...
body_2= chrono.ChBodyAuxRef()
body_2.SetPos(chrono.ChVectorD(0.5,0,0))
my_system.Add(body_2)
body_2.GetAssets().push_back(myasset)
 
#
# Create an exporter to POVray !!!
#
 
pov_exporter = postprocess.ChPovRay(my_system)
 
 # Sets some file names for in-out processes.
pov_exporter.SetTemplateFile        (chrono.GetChronoDataFile("_template_POV.pov"))
pov_exporter.SetOutputScriptFile    ("rendering_frames.pov")
pov_exporter.SetOutputDataFilebase  ("my_state")
pov_exporter.SetPictureFilebase     ("picture")
 # Save the .dat files and the .bmp files in two subdirectories,
 # to avoid cluttering the current directory...
if not os.path.exists("output"):
    os.mkdir("output")
if not os.path.exists("anim"):
    os.mkdir("anim")
pov_exporter.SetOutputDataFilebase("output/my_state")
pov_exporter.SetPictureFilebase("anim/picture")
 
 # Tell selectively which physical items you want to render, or use AddAll()
pov_exporter.Add(body_1)
pov_exporter.Add(body_2)
 
 
 # 1) Create the two .pov and .ini files for POV-Ray (this must be done
 #    only once at the beginning of the simulation).
pov_exporter.ExportScript()
 
 # Perform a short simulation
while (my_system.GetChTime() < 0.2) :
 
    my_system.DoStepDynamics(0.01)
 
    print ('time=', my_system.GetChTime() )
 
    # 2) Create the incremental nnnn.dat and nnnn.pov files that will be load
    #    by the pov .ini script in POV-Ray (do this at each simulation timestep)
    pov_exporter.ExportData()
 
 
 
# That's all! If all worked ok, this python script should
# have created a  "rendering_frames.pov.ini"  file that you can
# load in POV-Ray, then when you press 'RUN' you will see that
# POV-Ray will start rendering a short animation, saving the frames
# in the directory 'anim'.