calculation of observable area of an airplane?

I have an application where I need the observed equivalent area of an airplane in an arbitrary orientation. That is if the observer is directly under the AC the area would simply the be the 3-view top area, but what if the observer were 45deg behind the right wing and 30deg below the horizontal plane of the AC? I have been using an approximation that ignores wing area-this is no longer sufficient.

wikipedia has an ok article, by extension I could sum the three areas each corrected by cos(beta). But does not account for when one surface is partly hiding a second surface.

Currently I am using a simple method given 2d area and observed angle (cos(beta) effectively), I would consider a method that required 2d surface point definitions for top/left/fore.

Run time is not critical, provided I can sweep it into a 2d data table (range is handled by other means).

Any direction or key words to search on would be appreciated. thanks.

Answer 1

[John D'Errico]

I would...

1. Start with a triangulation of the surface of the airplane.

2. Given any point of view, project each triangular facet into the plane so defined by the viewpoint (thus normal to the viewpoint vector.)

3. Compute a polygon in the projected plane that encloses all projected facets.

4. Compute the area of the polygon.

While this scheme is a simple one that fails to correct for perspective, in the sense that facets that lie further away from the viewer should appear smaller, one could include that as an improvement easily enough.

[Chris Wilkening]

I get a bit lost with steps two and three, are there matlab functions for this? Can you post a link or two on how to code this up? I am not worried about perspective, I think that can be ignored for a long time to come.