Scripted transient thermal: how to extract end-of-step temperatures? (ThermoSensorExtractor.Results is None)

[241x049x]

I’m running everything via Python scripts (no UI). To reproduce liver motion, I move the organ geometry at each time step in both the EMLF simulation (to generate Phantom_Liver_i / Overall Field) and the transient thermal simulation. My goal is to use the final temperature at step i as the initial condition of step i+1—but I can’t retrieve temperatures programmatically.

Current behavior (brief):

Thermal sim runs, voxels created, .sab saved.

I attach a thermal.TransientFieldSensorSettings() (Temperature) to Overall Field, enable available store/write flags, and set snapshot times (0–5 s) on both Setup and sensor.

In simulation.Results(), I see ThermoSensorExtractor, but after Update() its Results is always None.

Log excerpt:

[DBG] ThermoExtractor ...
[DBG] Overall Field.Results type=<class 'NoneType'>

I tried various other methods to obtain the temperature, but they all failed.

Questions:

In the current API, what is the supported script-only method to obtain temperature values (per entity or field) at the last snapshot of a transient run?

Which exact settings/flags are required so that ThermoSensorExtractor (or an alternative extractor) returns non-None results?

Is there a minimal example showing how to:

attach the correct temperature sensor(s) to the right component,

trigger result generation,

and export the final-step temperatures for reuse as the next step’s initial condition?

I can share the script, logs, and .sab files if helpful.
Thank you!

Best regards

[bryn]

This is a simplified example (partly generated using the "To Python" action in the context menu). The example does the following

• creates an EM simulation as heat source
• creates a thermal simulation
• creates a "continue" simulation using the thermal distribution from the first simulation
• extracts the temperature field

from pathlib import Path

import numpy as np
import s4l_v1.document as document
import s4l_v1.materials.database as database
import s4l_v1.model as model
import s4l_v1.simulation.emfdtd as emfdtd
import s4l_v1.simulation.thermal as thermal
import s4l_v1.units as units
from s4l_v1 import Unit


def create_emfdtd_simulation():
    simulation = emfdtd.Simulation()

    entity__lines1 = model.AllEntities()["Edge Source"]
    entity__sphere1 = model.AllEntities()["Sphere 1"]

    material_settings = simulation.AddMaterialSettings([entity__sphere1])
    simulation.LinkMaterialWithDatabase(material_settings, database["IT'IS LF 5.0"]["Liver"])

    edge_source_settings = emfdtd.EdgeSourceSettings()
    simulation.Add(edge_source_settings, [entity__lines1])

    edge_sensor_settings = emfdtd.EdgeSensorSettings()
    simulation.Add(edge_sensor_settings, [entity__lines1])

    automatic_grid_settings = [x for x in simulation.AllSettings if isinstance(x, emfdtd.AutomaticGridSettings) and x.Name == "Automatic"][0]
    simulation.Add(automatic_grid_settings, [entity__lines1, entity__sphere1])

    automatic_voxeler_settings = [x for x in simulation.AllSettings if isinstance(x, emfdtd.AutomaticVoxelerSettings) and x.Name == "Automatic Voxeler Settings"][0]
    simulation.Add(automatic_voxeler_settings, [entity__lines1, entity__sphere1])

    simulation.UpdateAllMaterials()
    simulation.UpdateGrid()

    return simulation

    
def create_thermal_transient(em_overall_field):
    simulation = thermal.TransientSimulation()

    entity__sphere1 = model.AllEntities()["Sphere 1"]

    material_settings = simulation.AddMaterialSettings([entity__sphere1])
    simulation.LinkMaterialWithDatabase(material_settings, database["IT'IS LF 5.0"]["Liver"])

    initial_condition_settings = thermal.InitialConditionSettings()
    initial_condition_settings.InitialTemperature = 37.0, Unit("C")
    simulation.Add(initial_condition_settings, [entity__sphere1])

    transient_heat_source_settings = simulation.AddHeatSourceSettings([em_overall_field])

    automatic_grid_settings = [x for x in simulation.AllSettings if isinstance(x, thermal.AutomaticGridSettings) and x.Name == "Automatic"][0]
    simulation.Add(automatic_grid_settings, [entity__sphere1])

    automatic_voxeler_settings = [x for x in simulation.AllSettings if isinstance(x, thermal.AutomaticVoxelerSettings) and x.Name == "Automatic Voxeler Settings"][0]
    simulation.Add(automatic_voxeler_settings, [entity__sphere1])

    simulation.UpdateAllMaterials()
    simulation.UpdateGrid()
    
    return simulation

if __name__ == "__main__":
    # create dummy model
    line = model.CreatePolyLine([model.Vec3(0,0,20), model.Vec3(5,0,20)])
    line.Name = "Edge Source"
    
    sphere = model.CreateSolidSphere(model.Vec3(0,0,0), radius=15)
    sphere.Name = "Sphere 1"
    sphere.MaterialName = "Liver"

    # create heat source
    em_sim = create_emfdtd_simulation()
    em_sim.Name = "EM Heat Source"
    document.AllSimulations.Add( em_sim )
    
    # setup initial thermal simulation
    th_sim = create_thermal_transient(em_sim.AllComponents["Overall Field"])
    th_sim.Name = "T Initial Simulation"
    document.AllSimulations.Add( th_sim )
    
    # setup simulation using result from previous simulation
    th_continue = th_sim.CloneWithDiscretization()
    th_continue.Name = "T Continue Simulation"
    
    init_cond_settings = th_continue.GlobalInitialConditionSettings
    init_cond_settings.InitializationOptions = init_cond_settings.InitializationOptions.enum.ContinueSimulation
    init_cond_settings.InputSensor = "Overall Field"
    init_cond_settings.InputSimulation = th_sim.Name
    
    document.AllSimulations.Add( th_continue )
    
    # run simulations
    project_file_path = Path.home() / "t_continue.smash"
    em_sim.CreateVoxels(project_file_path)
    em_sim.RunSimulation()
    
    th_sim.CreateVoxels(project_file_path)
    th_sim.RunSimulation()
    
    th_continue.CreateVoxels(project_file_path)
    th_continue.RunSimulation()

    # extract some results
    th_continue_extractor = th_continue.Results()
    th_sensor_extractor = th_continue_extractor["Overall Field"]
    th_sensor_extractor.Outputs["T(x,y,z,t)"].Update()
    field = th_sensor_extractor.Outputs["T(x,y,z,t)"].Data
    print(field)