## Introduction

The Mass Properties analysis follows the component priority rules and will compute the masses and inertias from individual bodies into the total. Components may have volume density, surface density (mass/area), or a combination. However, as of version 3.31.1, interior thin surface densities are ignored by the analysis, regardless of priority. For example, a tank of priority 1 with both surface and volume densities modeled entirely within a fuselage of priority 0 will only contribute its volume density to the mass while the surface density is ignored. To get around this limitation, a step-by-step approach is recommended in which different priority levels are analyzed separately and accounted for.

## Introduction

The Mass Properties analysis is a way to capture the masses, moments of inertia, and center of mass locations in an OpenVSP model or set. The density and mass/area for each component are used to compute the individual contributions to the total. Mass properties are computed by slicing the model in the X-direction with a set number of slices, meaning that a more accurate mass buildup will be achieved with more slices. Also recall that component Priority determines the hierarchy of overlapping or internal components in which higher priority values will override those of lower value e.g., priority 2 will take precedence over priority 1 and 0. This is very important to keep in mind when producing mass buildups for complex models with multiple internal or intersecting components. Blank components may also be used to define point masses in this analysis.

More information on component mass properties are available in the General Component topics:
Mass Property: Fundamentals
Mass Property: Priority and Intersection

## Introduction

The Planar Slice tool analyzes the as-displayed wireframe of the OpenVSP model, with the set tessellation and clustering shown in the workspace, as opposed to operating on the Bezier surfaces themselves. This means that higher surface resolution is needed to obtain more accurate slice areas. Planar Slice also detects whether a slice passes into or out of a body including cases where geometries wrap back on themselves such as with flow-through components. Similar to other triangulation operations like Comp Geom, Planar Slice will also analyze imported meshes.

## Introduction

The Planar Slice tool is another triangulation and intersection algorithm within OpenVSP. Executing the analysis will produce an array of slices defined by the user in the X, Y, or Z directions, including taking a single slice, and report the center location and area of each slice. The bounds of the analysis may be automatically set to capture all relevant components or manually set within defined start and end locations.

## Introduction

The Comp Geom tool is a geometry intersection and analysis algorithm that will compute the theoretical and wetted areas and volumes of your OpenVSP model, producing an intersected triangulated mesh. Comp Geom is widely integrated into other analyses and functions within OpenVSP such as VSPAERO’s Panel mode and the Parasite Drag tool.

Component subsurfaces may be included in the analysis to separate regions of a body or wing. A semi-span or half-mesh model may be generated normal to the XZ plane, if desired.

Users may choose between the “Normal” set, which analyzes the geometry surfaces as thick bodies, or the “Degen” set, which degenerates the included components to their camber surface representation before analyzing as thin surfaces. This enables the generation of hybrid thick/thin meshes.