Relatively simple perspective question

[Chuck Yokota]

Ken,

Um, I guess I thought it *was* the simple way. I got my stuff from a course in geometric modelling, a graduate-level engineering class in the mathematics behind how computers generate real-time 3D scenes onto your monitor. The course started out assuming you were familiar with matrix algebra, vector and tensor calculus, and differential equations, and then got into the complicated stuff. Plan perspective was tossed out as a simple, intuitive way to picture what was going on when the computer was crunching bits.

As Allan says, you can paint any scene by painting through an imaginary frame, from life.

I suppose the next simplest way is to use a reference photo and accept whatever distortions are created by the camera lens.

[Steven Sweeney]

Limiting this response to the desired representation that was described

[Geary Wootten]

Originally Posted by Steven Sweeney

.........Voila, and it hardly even hurt.

......Qww - ya wanna bet? LOL.

Steven, Ken..et al,

Thanks for taking the time in doing this. In spite of my yucking it up, I actually learned some things today.

G. (reeling from left brain hook to right brain. )

[Steven Sweeney]

So, okay, I added the supporting illustrations above. That

[Allan Rahbek]

Steven

There is no "true" perspective, all of them are theoretical, fulfilling different needs. I try to avoid the use of linear perspective.

How did you place the two vanishing points ? Did you measured them to the right place or how ?

I think Ken will have troubles drawing in a small boat cabin. It is tempting to take a broader view when drawing in a small room. When seeing the drawing from a longer distance (than it was done) you will see distortions.

I will attach a drawing that, hopefully, will explain the perspective consequence of doing the wide angle view.

Allan

[Ken Smith]

Wow!

I'm suitably amazed. I never thought of myself as particularly left-brained, but this sure cinches it.

Last evening I actually was able to do the drawing using the plan perspective thing, and surprisingly (to me, anyway), it actually worked. Except that I made the horizon too low.

The reason I'm exploring this is that I'm doing a painting of 3 guys in the cockpit of a LCVP (a WWII landing craft). I have some 1/24 scale blueprints of the boat and a very poor plastic model and a bunch of photos (but of course none from the angle I need). I need to place these guys accurately to get the scale of the boat and a realistic view of the various angles.

After reading all this, and trying my own descriptive geometry session, I've decide to solve it this way:

I've taped out the layout of the cockpit full-size on the floor of my studio. I'm going to roughly mockup the sides and deck heights and so forth with some corrugated cardboard sheets, and then place the models where they belong, light them, sketch them, photograph them, and let that be that (and just be glad they weren't on an aircraft carrier!).

This has been a supremely informative discussion; I really appreciate all the info (and I actually sort of understand it, which I certainly didn't beforehand).

[Steven Sweeney]

How did you place the two vanishing points ? Did you measure them to the right place or how?

Allan,

You are astute to ask this question. In fact, in my quick sketch, I just located the vanishing points where it was convenient to do so. More correctly, one would have to establish a so-called "circle of view", the radius of which is the distance from the viewer to the image plane (or drawing). From any point, then, on that circle, the vanishing points would be 90 degrees apart (using the point on the circle as the vertex of that angle.) This gives you an infinite number of available perspectives, though a relatively small number of them will produce aesthetically pleasing results, which for our purposes here is the primary consideration.

A caveat, that this is the procedure for the cubic polyhedron. Other forms require modification of this approach.

All of which is why I suggested that Ken focus on what he could see, with an eye to aesthetic considerations, rather than worry about precision in perspective.