After installation, when you start Rhino 8 and issue the “Grasshopper” command, Grasshopper starts but Intact.Simulation is not visible in the toolbar menu. In the Rhino command output, there is the following error:

An error occured during GHA assembly loading:
 Path: %APPDATA%\Roaming\Grasshopper\Libraries\Intact.Simulation\IntactGrasshopper_Plugin.gha
 Exception System.IO.FileNotFoundException:
  Message: Could not load file or assembly 'System.Runtime, Version=7.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' or one of its dependencies. The system cannot find the file specified.

This error message indicates that Intact.Simulation for Grasshopper cannot be loaded. This issue occurs because Rhino 8 can be started in one of two modes: one that is compatible with older plugins using the .NET Framework 4.8, and one that is compatible with newer plugins using .NET Core 7, which is what Intact.Simulation for Grasshopper uses.

Following Rhino’s official documentation, we recommend creating a shortcut to start Rhino 8 using .NET Core 7. Create the shortcut by navigating to the Rhino installation location (usually C:\Program Files\Rhino 8\System\Rhino.exe), right-click on it, create a shortcut, then right-click on the shortcut to edit it to start Rhino 8 as

"C:\Program Files\Rhino 8\System\Rhino.exe" /netcore

This will start Rhino 8 in a mode that is compatible with Intact.Simulation for Grasshopper. You may also want to create a similar shortcut to start Rhino 8 in a mode compatible with older plugins.

A: Issues with the parameters of your simulation are the result of an invalid/incorrect input.
The solver block is where the inputs are compiled, so work backwards from there for troubleshooting. An issue with solver settings parameters will not cause the simulation to be unsolvable, so the solver settings input [SS] can be ignored. While troubleshooting inputs, use the default solver settings.
Components [C]: Are your geometries connected to Intact Component blocks? Are you defining an appropriate material (make sure to not use thermal materials for stress simulations and vise versa)
Restraints [R]: If you are using fixed restraints, are your geometries attached to a fix restraint block? If you are using displacement boundary conditions, do you have an x, y, and z displacement defined? It is required to have all three translational degrees of freedom defined.
Loads [L]: Double check all parameters on your loads have been defined. Ensure the load is being placed in the place you want it to be (check geometry). Are you connecting body loads to the loads input? If so, connect those to LV.
Body Loads [LV]: This input is for body loads only. These are body weight loads and linear/rotational acceleration loads.
An example of the setup process can be found here Simulation of a Bonded Assembly.

B: The most probable reason for this problem is an incorrectly placed geometry. Each place you reference a geometry from Rhino, select the geometry with the preview enabled. Ensure the geometry it highlights in Rhino is correct.
Also, enable the preview on the solver block. Ensure the loads and restraints are at the right location on the geometry.
Make sure that referenced geometries that are supposed to intersect actually intersect. A load that isn't connected to your geometry can be a reason for this result.

C: Make sure you are not closing the command prompt window that appears when you click solve. Another good thing to check is the specifications of your system, so you can learn the limits of the computer you are running simulations on. This will primarily be dependent on how much RAM you have. Switching to the iterative solver will be beneficial if your system has limited RAM.

D: Your issue is setting too high of a resolution or too small of a cell size. If you have made your cell size very small to capture small portions of your geometry, increase the cell size. Increasing the cell size decreases the resolution. If the simulation initially said solved, but you couldn't select a solution quantity, your system likely ran out of RAM. Start at a small resolution that solves quickly. For simulation to inform design, a high resolution is not required. If you are running a simulation for very accurate results, increase the resolution by doubling/tripling it until the simulation returns a converged solution. Using the iterative solver is advantageous for decreasing RAM usage.
To learn more about cell size, resolution, or the other solver settings options, visit the solvers settings section of the FAQ page.

E: First, refer to section A to see if that solves your problem. Also, ensure you are not closing the command window that appears when you are running the simulation. If you believe your input parameters are set up correctly and are still having issues, please contact us and we will work with you to find a solution. Please contact us if you have additional questions or this guide didn't solve your issue.