[feral715]

Anyone know how to figure the sides of a square in perspective? Assuming the square is not exactly in the middle of the vanishing points. To be more explicit: If I choose two vanishing points, draw the length of one of the sides, how do I determine the length of the other side? Not sure how to upload images so I'm just hoping it works.

Thanks




[http://www.socalartstudios.com/pages/hiddenlinks.htm][/img]
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Don Flaws
http://www.donflaws.com

[feral715]

if you want to bother you can cut and paste the URL above to see the image. It's easier to show the question then to explain it.
thanks again
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Don Flaws
http://www.donflaws.com

[neff]

ehem... google?

http://www.google.de/search?q=perspective+square&ie=UTF-8&oe=UTF-8&hl=de&btnG=Google+Suche
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[dzou]

if you think about it it will become obvious





if the pic don't work goto

http://iquebec.ifrance.com/projet00/Image-13.jpg

[Kevinski]

dzou is correct..
this is the right perspective for your problem,
however, the reason that the square appears so distorted is down to the field of view .FOV(Roughly 100 degrees). Like a wide angle lens on a camera, your perspective lines are converging more rapidly.



Quantifying this effect is more difficult, but with your center viewpoint, extending your VP's apart will bring your FOV down to a more natural look without moving the central position of the square.

good luck.

[DJorgensen]

Oh wow! I never noticed that... It makes it seem so simple now

Great question feral715!
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[jfrancis]

Very interesting. I didn't think there was an optical solution other than to use instinct.

Now that I see what you're driving at, assuming I understand it, I think I can even slightly simplify it:

Connect the lower corner diagonally across the square through the upper corner and straight at the midpoint between the two VP's. Wherever the diagonal across the square intersects the known edge is the point where you need to draw the unknown edge.

Yes?