The topics below demonstrate how to use the Snap-To feature in OpenVSP. Snap-To is an interactive collision detection function that enables placing components at a fixed surface normal distance from one another or to check for clearance or collision in a model. For example, a component may be rotated or translated through a range of motion to ensure that adjacent parts are not struck. Alternatively, a component may be placed a fixed distance relative to another set of components with a single click.
User Parameters are unique variables that you can leverage to control or link your model in ways that aren’t available by default in OpenVSP. There are always 16 predefined user parameters that will always have the same Group, Name, and ParmID regardless of which model you are using. This makes them very robust in scripting and automation. Perhaps of greater interest to the designer is the ability to create custom parameters and adjust them from this menu. Once a user parameter has been created, the parameter is available for adjustment or linking as with any other model parameter. For example, a wing may be sized according to gross weight and wing loading rather than by span and area. An propeller may be sized according to the thrust, disk loading, tip speed, etc. So you can see how leveraging User Parameters in your model can enable a wider variety of parametric variation than would otherwise be available by default.
Variable Presets are an incredibly versatile and powerful function within OpenVSP that enable multiple, preconfigured parameter settings to be swapped with the click of a button. Variable Presets differ from Design Variables in that the presets are not intended to be interacted with or altered outside of OpenVSP for large design space explorations. Rather, the presets are intended to act as stored configurations of various settings that can be quickly switched within the GUI. For example, you can use the basic frame of a transport aircraft and variable presets to switch between different manufacturers and passenger classes in a single model. You can quickly switch between low, medium, and high resolution surface tessellation. You can also save analysis input settings (such as VSPAERO) to quickly set up and run different conditions. The possibilities are relatively boundless with this feature.
Design variables are a great way of organizing your most important or most often used parameters into a single location for easy access and manipulation. You may also save the design variables to a text file that can be loaded at any time to update your model. These text files can be edited outside of OpenVSP either manually or by scripting/automation and then used to rapidly update models with parametric variations on design trades. This is a nice way of handling trade studies and systems analysis without having to build the API or write in AngelScript.
Similar to isolating OpenVSP components in Sets for analyses or visual grouping, you can also define specific sets of components to be included or excluded in a file export. For example, if you have many internal components that serve as masses or for cabin layout it is unlikely that you want all of these included in an outer mold line for aerodynamics, 3D printing, meshing, etc. Simply place the relevant components into a new Set and export by choosing that Set from the dropdown menu (File > Export… > Normal Set menu).
Component Sets may also be saved as a new OpenVSP model with an important caveat. The component hierarchy in the Model Tree must be preserved for the model to save the Set, meaning that the individual components and ALL relevant ancestor/parent components must also be included in the saved Set.