Most lift and drag calculations require the use of a frontal/projected area. This is normally not that big of a deal, especially when dealing with nice clean CAD files. Unfortunately, in fast-paced design environments (motorsport especially), you'll often get a collection of STL geometry files instead. This is annoying for a number of reasons, but mainly because there are several methods for computing the frontal area of an STL and all of them involve a fairly tedious/lengthy process. pArea aims to solve this with a single command.

Installation

pip install parea

Usage

As a simple example, the cube STL located within the tests directory has a projected area of 4.0 along all three coordinate axes. To validate this, simply run the following (assuming you've downloaded cube_ascii.stl into your current working directory):

parea -stl cube_ascii.stl -x

For models comprised of multiple STL files, simply separate the file names with a space:

parea -stl file_1.stl file_2.stl file_3.stl -x

Or use shell-style wildcards:

parea -stl file_*.stl  -x

When simulating ground vehicles with non-rigid wheels, you will need to account for the tire deformation and subsequent ride height drop. This can be facilitated using the -floor flag followed by a floor height float value. Note that floor height is in reference to the vertical axis of the specified projection plane.

parea -stl file_*.stl  -x -floor 0.0125

Since the projection vector is x, our projection plane is therefore yz yielding a projected area based off all geometry above z=0.0125.

Options

vectors: -x, -y, -z

planes: -yz/-zy, -xz/-zx, -xy/-yx

References

• Computational Geometry: Algorithms and Applications (3rd Edition) by Mike de Borg, Otfried Cheong, Mark van Kreveld, and Mark Overmars
• Computational Geometry in C (2nd Edition) by Joseph O'Rourke
• Finite Element Mesh Generation by Daniel S.H. Lo