Shadows on Fuselages

[Vacajun]

GM and I had several discussions on whether curved shadows exist a few years ago that stimulated some discussion. It was based on my observations of shadows created by a simple business card and tube model outdoors in the sun and then with a ray-tracing program. Unfortunately, the thread was lost when the site went belly up, so I thought I'd re-post the main points for comments, criticism, and whatever other tomatoes get thrown.

The computer-generated sketch shows the simple tube with three different "wing locations above it. From left to right, the wing is swept back, the middle one is unswept, and the one on the right is swept forward.

The sun is at the 2:00 position, coming from the right. Let's consider the middle model first. With no sweep, the shadow will cut a straight line across the "fuselage." So if the shadow-producing surface (wing, tail, etc.) has no sweep, the shadow will not have curvature, even if the fuselage (wing tank, etc.) is circular.

The model on the left shows that a swept-back wing will produce curved shadows on the curved fuselage, but it takes quite a bit of sweep to show up. Notice the direction of curvature. This effect is quite noticeable on wing tanks for the F-106 with its 60 degree sweep. Also, the shadow will not be curved on a straight-sided surface, even though the wing is swept back.

The model on the right shows that the swept-forward wing also produces curved shadows, but they are curved in the other direction. Again, it takes a lot of sweep for the effect.

Now things will get interesting for a wing having modest leading-edge sweep and a larrge forward sweep to the trailing edge. The leading- and trailing-edge shadows will curve in different directions.

I think it helps to visualize the wing's shadow as a solid object beneath the wing which cuts into the curved fuselage causing a cuved shadow.

Finally, please note that these particular situations only exist for the sun location I used. If the sun is abeam (as pssask sometines uses) the shadows will be completely different.

Sorry for being so long, but maybe the info will help someone.

Joe

[inkworm]

Excellent post that should clear up all arguments!

[Supah]

But sometimes reality does not look very good in profile

[BLOWHARD]

And sometimes reality isn't something that needs to be argued when talking about profiles.
If the artist likes it and thinks it looks right, that's good enough

Nice visuals Joe!!!

[JMSmith]

i, of the flat earth society, believe this is not true,

shadows should be straight, unless the object casting the shadow is curved

[Vacajun]

Aw C'mon John-- come over to the Dark Side!

[Jesters-Ink]

Just for the hell of it, I'm standing shoulder to shoulder with John, in the light.

[Supah]

Poor 1-0-6, about to be blown to smithereens!

[mclaring]

If John says the earth is flat, then I am with him. Those of you not with us are against us,

MC

[Mangas]

Everybody above are wrong.
See the image posted thoroughly... Actually, no matter what form does the object (that drops shadow) has... It's the form of the object that has this shadow on him that really (visible to us) matters... If it's a cyllinder -- the shadow edges will be curved (even if dropped from the plain/flat crap)...

But what is most important is that most aircrafts have absolutely different fuselage cut-views... God helps those who consider them all as just cylinders...