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  • Installing Sim4Life and configuring licenses

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    M
    Hi, yes, we have new agent in China and the contact email is zmt_china@163.com.

  • Working with CAD models

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    Hi everyone, I am experiencing several rendering issues with the Sim4Life 3D Viewer when running Sim4Life on a Windows server through Remote Desktop (RDP). Colors change when selecting an individual model element. When I select the Model folder in the Explorer, all elements are displayed correctly: [image: 1786565631056-screenshot-2026-08-12-161301-resized.png] However, as soon as I select an individual element within the folder, the colors of the model change significantly and no longer correspond to their normal appearance: [image: 1786565696244-screenshot-2026-08-12-161442-resized.png] Elements disappear when opacity is below 100%. If I change the opacity of any element to a value below 100%, the element completely disappears from the 3D Viewer. At the same time, the colors of the remaining model are also altered, even when I select the entire Model folder again: [image: 1786566049952-screenshot-2026-08-12-162026-resized.png] [image: 1786566083849-screenshot-2026-08-12-162105-resized.png] The server has the following specifications: OS: Windows Server 2019 Standard, version 1809, build 17763.8755 CPU: Intel Xeon Platinum 8160 @ 2.10 GHz RAM: 1.50 TB System: 64-bit OS, x64-based processor GPUs: NVIDIA Quadro P1000, NVIDIA Tesla V100-PCIE-32GB NVIDIA driver/OpenGL information: Initialized OpenGL view 4.6.0 NVIDIA 539.64 [Quadro P1000/PCIe/SSE2], backwards compatible, 8 multi-samples Connection: Windows Remote Desktop (RDP) Sim4Life version: 9.4.2.21604 The 3D Viewer itself initializes successfully, but these rendering problems persist. Does anyone know what could be causing this or how to fix it? Thanks!

  • Working with models from the Virtual Population

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    J
    Good evening. Please, I want to ask if there is a model or phantom that contains the lower limb tibial nerve. Best regards,

  • FDTD, Low-Frequency, Neuron, Mode-Matching, Flow, Acoustics, etc...

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    V
    Hello, I am setting up an LF Electro Ohmic Quasi-Static simulation using the DUKE_POSABLE 3.2 model. I have placed two solid spherical electrodes in contact with the body and applied Dirichlet boundary conditions. After voxelisation, the electrodes appear hollow or lattice-like, as shown in the attached screenshots, even though the original geometries are solid. I used a local 1 mm grid for the electrodes, while the anatomical model has a maximum grid step of 2 mm. Could you please explain what may be causing this appearance? Is it only a visualisation effect, or does it mean that the electrode interiors have not been filled with voxels? If the electrodes are actually voxelised as hollow structures, could this affect the electrical contact with the tissue, including the calculated current distribution or contact impedance? Also, is there a way to check whether the electrode material has been correctly assigned throughout the entire electrode volume? Thank you. Here is the screenshort of the voxel: [image: 1789648394768-screenshot-2026-09-17-104009.png] Screenshort on simulation settings: [image: 1789648532529-screenshot-2026-09-17-104234.png]

  • Postprocessing results

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    Z
    Hello, I am having an issue when evaluating SAR results in Sim4Life. When I try to view the SAR result (e.g., psSAR IEEE/IEC 62704-1 Avg.SAR(x,y,z,f0)) over the original simulation domain, Sim4Life reports an error indicating that the grid is too coarse, and I cannot obtain the SAR result. However, if I first use Crop to reduce the analysis region to a smaller area around the region of interest, the SAR evaluation works and I can successfully visualize the SAR distribution. The underlying simulation results and grid remain unchanged; I am only changing the spatial region used for post-processing. Could you please clarify why cropping the analysis region changes whether the SAR evaluator considers the grid sufficiently fine? In particular: Could a coarse-grid region somewhere outside my region of interest cause the SAR evaluation for the whole domain to fail? If the SAR result becomes available after cropping out those regions, can the SAR values within the cropped region be considered valid, or should I refine the simulation grid and rerun the simulation? Thank you for your help.

  • Scripting interface for Sim4Life

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    R
    thanks Robin!

  • Running Sim4Life over a network

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    ofliO
    Hi, Please allow me to share here the response we sent you via the Sim4Life support email so that other users can benefit from your questions. The default machine provides 500GB of storage, and you are running out of space for this project. If your results require more than 500GB, consider upgrading to a higher-tier machine with greater storage capacity. Alternatively, you could reduce the size of your simulation project by splitting it into multiple smaller simulations. This would allow you to continue using the default tier. Additionally, you might optimize your sensor settings, such as by creating smaller sensors and recording data for specific volumes of interest, rather than using an Overall Field sensor.
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    Billie_V2_skin_functionalized.sab file for optimization tutorial

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    J
    Yes, I am working on sim4life.lite version Thank you very much bryn
  • T

    Electro Ohmic Quasi-Stat Normalization

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    When you use the normalization option, Sim4Life: Computes the current flux through an automatically generated iso-potential surface Scales all output quantities so that the resulting current matches the value specified in the Normalize Frequency-Domain Results field The current value you enter represents the phasor amplitude, i.e. the baseline-to-peak current. For more information, please refer to the Sim4Life Manual Section 2.13.7.3.3 Normalization -- Normalization to Current.
  • M

    Export Huygens Source

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    H
    Hi @MB, The solution would be to export a separate Huygens source for each port individually (i.e., without using the Simulation Combiner). You can then set the amplitudes and phases of each Huygens source when you use them. This approach is quite powerful if you need to simulate multiple amplitude/phase configurations. However, we understand this might be a concern if you have a large number of ports involved. That said, we’re aware of this limitation and are working on adding this feature in an upcoming release.
  • R

    sim4life.lite Tutorial

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    S
    The guided tours within the tutorials are indeed not working as intended. Thanks for pointing this out! Instead, I would recommend following the instructions in the text documentation of the tutorials: https://manual.sim4life.io/manual/Tutorials/index.html Let me know if you run into issues with a specific tutorial!
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    Electrode with Nerve Model tutorial

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    Hi @cbenj33 we are aware of the inconsistencies (we have changed the position of the nerve and electrode, which will be part of the next release happening soon). For now, I am emailing you the pdf version of this tutorial documentation and explanations regarding the errors.
  • M

    What does this mean?: Error : Geometry cache out of date, unable to continue voxeling.

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    brynB
    The voxeler (re-)uses cached information about the geometry (solids, wires, etc.). It looks up the information for each model entity and emits this message if the cached geometry was not found. Questions: are you running this in the GUI or a script/notebook? did you potentially delete (or modify) some of the entities assigned to the simulation (I guess in voxeler settings)? If you deleted the entity or modified it in the modeler (some operations preserve the instance, while others may create a new instance and delete the old one), this would explain the error. We could improve the error message by providing more helpful instructions.
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    This topic is deleted!

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  • R

    Volt and sensitivity of transducer sim4lite

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    M
    Assuming a linear relation between voltage and pressure amplitude, you should be able to map the input voltage to the input pressure (I think its 1 MPa by default), and then use this as a scaling factor, but it's unclear to me what you mean with voltage at the focused area. What exactly do you mean by transducer sensitivity? You could run additional simulations where you shift the transducer or slightly change some parameters to get a sense of the sensitivity.
  • A

    How to Script the Import a Segmented NIfTI Volume as a Solid in Sim4Life?

    image model python
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    brynB
    Here is a simple implementation to write an iSEG tissue list file, given a dictionary mapping the label index to a name: https://github.com/dyollb/s4l-scripts/blob/df8e2241f87ca91d71138e9d2b3d4336dadb82dc/src/anisotropic_conductivity/load_labels.py#L44
  • vegogardenV

    This topic is deleted!

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  • J

    Cannot open .smash project file

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    J
    Thank you so much you are a godsend You saved me a couple days worth of work!
  • L

    Heat generation rate and Heat transfer rate in a MQS/Thermal simulation

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    In terms of the material settings in the thermal simulation: The heat transfer rate defines whether heat removal by perfusion should be considered. In the absence of this term, heat is only removed by thermal conduction (diffusion) and boundary conditions. The options provided for heat transfer rate affect whether perfusion is constant or affected by local thermoregulation (temperature (T) dependent perfusion, e.g., to account for vasodilation). As for the heat transfer rate, the heat generation rate term can be constant or affected by local thermoregulation (T dependent, reflecting increased metabolic activity with increasing temperature). It is also possible to introduce time-dependent heat generation, e.g., to model a heating battery. Baseline perfusion values (incl. variability information) are available in the IT'IS database and can be automatically assigned from sim4life: (http://www.itis.ethz.ch/virtual-population/tissue-properties/database/database-summary/). If non-constant perfusion should be applied or not depends on the tissue and temperature increase magnitude (e.g., muscle above 39 starts to have a strong perfusion increase). The conservativeness of a perfusion model choice is application-dependent. To simulate the heating effect of tissues over time, blood perfusion and heat generation rate (metabolic heat generation) of the tissue would also need to be considered. The perfusion is covered in the option "Heat Transfer Rate". All options that you can enter here are related to heat-transfer based removal of energy from the system. Perfusion can be adjusted by changing the type of hear transfer (None, Constant, Linear (T), Piecewise Linear (T). The constant term assumes constant perfusion, independent of tissue temperature. It is the default assigned when using the IT'IS tissue database in Sim4Life. Linear (T) or Piecewise Linear (T) assume temperature dependent perfusion. You can add your your transition temperatures using the little "+" icon. Please note that the linear coefficients represent the slope of the linear perfusion. Each transition temperature indicates the change of the perfusion rate.
  • Paria M.P

    Grid Convergence

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    To perform such a study, define your region or quantity of interest, then parametrize it. After a quantity has been parametrized, you can run multiple simulations using the built in Sweeper feature or using the Sim4Life Python API. There is an example in the Sim4Life manual titled 'Parametrized Patch Antenna' that shows how to use the Sweeper feature. If using the Python API, the easiest way would be to create a baseline simulation by hand, then right-click on the simulation name and select To Python. Then you would find the quantity of interest in the auto-generated script and assign it to a variable instead of the hardcoded value. Using a simple loop in Python, you can create multiple simulation that have identical setup except for parameters of interest. In your example, multiple simulations would be run with identical setup except for the grid resolution within a region of interest (e.g., a wire block surrounding a region of interest is placed in a manual grid settings folder, then Maximum Step is changed from 0.3 to 1.0 mm). Then in Analysis you extract a quantity of interest and compare how this value changes as a function of grid resolution. If the change in the value is small as you increase resolution, you can proceed in future simulations with a coarser resolution to save on run time. The exact convergence of the value needed depends on your application.
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    This topic is deleted!

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    My S4L file isn't opening after it crashed

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    D
    @bryn Thank you Bryn. Managed to find a version that wasn't corrupted! Hope you have a nice day
  • L

    3D Surface model to Voxel and export

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    brynB
    Are you using Sim4Life lite (web version)? I recorded my screen while I voxeled Duke V2.0 and exported the voxels. There seems to be a glitch in the Reload button when I try to see the data that was saved in the Study: as a workaround the Reload button in the DATA tab works. I voxeled at 15mm, so the skin is not completely closed, but if you choose something like 5-10mm it should be enough to resolve thin layers (like the skin): BTW. if you are using a desktop version of Sim4Life, the workflow is similar, except that the software uses native Windows file dialogs to save/load files. https://youtu.be/uAQgQQpG3Bg
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  • glasshousemediaG

    This topic is deleted!

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  • A

    Simulate a concave multi-element ultrasound array

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    Assuming 'sim' is the acoustic simulation you're interested in and that 'elements' is a list of the elements (gotten from entities = model.AllEntities()) and that 'amp' and 'phase' are numpy arrays with the amplitude, phase values you're interested in assigning: # Print current simulation name print(sim.Name) # Remove all sources before adding them to_del = [] for s in sim.AllSettings: if isinstance(s,acoustic.SourceSettings): to_del.append(s) for d in to_del: sim.Remove(d) # Add sources with correct element and parameters for source_idx in np.arange(len(elements)): source_settings = acoustic.SourceSettings() source_settings.Amplitude = amp[source_idx] source_settings.Phase = phases[source_idx] sim.Add(source_settings, rings[source_idx]) print(rings[source_idx].Name, amp[source_idx], phases[source_idx]) Sorry I'm not providing a full example. Easiest way to do that would be to manually create the whole simulation without the sources (just make all sources as materials), then right click on simulation and select 'To Python...' and then add the lines above to your code You could do something like this to get the elements as a list: src_ents = [] entities = model.AllEntities() for e in entities: if 'Element' in e.Name: src_ents.append(e) Careful, I have no idea how the elements will be sorted in that case but you could use a fixed size numerical suffix and then sort them.
  • B

    File .Smash error

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    Hallo, There should be, in the same folder where the smash project is, a file named as the smash file, but starting with a ".", like ".Name_of_the_File.smash.xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx". Try to drag that file directly into Sim4Life and save it with a different name. From there you should be able to go on with the models/simulations/analysis settings already saved.