View Full Version : Need help with perspective

07-26-2007, 10:50 PM
I'm trying to draw an inside view of an O'Niell cylinder.

But I can't figure out how the builduings should taper of to the right and the left. I need a way to figure this out with rulers and stencils.


07-26-2007, 11:01 PM
I just posted a tutorial for two-point perspective on the tutorials forum.

However if you want single-point perspective the same applies. Pin a ruler to your vanishing-point, and draw your lines of parallel radiating from the single perspective.
You can also use successive division of your radial lines to approximate the equal divisions appear to bunch up with distance.

Eg: Draw your radial lines, divide them in half, then divide the segment closest to the vanishing-point in half. Repeat until your distance is trivial.
Use 'fogging' for distance cueing of far detail. Make your far colours cooler (tending toward bluish) to imply the scattering of light through the atmosphere.

07-27-2007, 08:34 PM
Thanks. That helps a bit.

I just realized that the round stencil I am using needs to have the same diameter as the O'Neill-cylinder in the drawing would have if it were real... I checked up on the price of RAM yesterady, I ordered a Gig as it cost about half of what I thought. An extra gig of ram wouldn't be enough for a round stencil with a diameter of a few kilometers, would it?

I guess I have to make some compromises if I wish to make something out of this drawing.

07-27-2007, 08:40 PM
Though just for curiosities sake. The round stencils Diameter should be half the diameter at the middle of the radial lines and minus the diameter of the far end of the cyliner. Right?

07-27-2007, 10:43 PM
It might pay to rough-out your your cylinder and basic internals using a 3D CAD app, set your camera to see how it converges. Then you can use that as a tracing overlay to guide the proportions of your painting.

07-27-2007, 11:18 PM
I was about to ask where I could find a good free cad program when I remembered that Iv'e seen a person do 3d art in a Half life map editor.

I don't have Half Life, but i do have Unreal Tournament 2004. And it comes with a map editor. See attached file.

Thanks for the suggestion! Pure genious!

07-28-2007, 07:55 PM
Yep, that's about right. The "ground" - the side of the cylinder you stand on - will seem much flatter than the "sky", simply because it is closer to you and the curvature is less evident. The wider the cylinder, the flatter will the ground seem.

Make sure you take atmospheric haze into account. If the cylinder is 1 km wide, and filled with the air completely (which at normal pressure it must) it will be enough to attenuate the "sky" rather blue. At 5km wide you'll see only the brightest spots on the opposite side, kind of as you can see the lit side of the moon in daytime, but not the dark one.