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View Full Version : Perspective -- Please Help!


prochristi86
04-11-2007, 10:41 AM
Hey,

Can someone PLEASE show me a straightforward and clear way to draw perfect cubes in 3-point perspective and draw a perfect square floor tile in 2-point, that can be used in any perspective situation? I know there's a cone-of-vision method or something that can be used, but I'm having problems with it. I am losing tons of time beccause of these difficulties (others are too, I'm sure).

Much appreciatively,

James Smith

GW.Fisher
04-11-2007, 04:56 PM
http://mathforum.org/sum95/math_and/perspective/perspect.html

prochristi86
04-11-2007, 08:43 PM
... I'm not sure I want to use math (not that I dislike it or find it really tough, thankfully!), but I would prefer NOT to use a mathematical approach when actually illustrating. Is that what YOU use, though?

I'm wondering about this: Here (http://studiochalkboard.evansville.edu/lp-in2.html) is some intersting information and this picture:

http://studiochalkboard.evansville.edu/chlk/lp-in2.gif

They say, "Divisions in the floor are best approximated, [and] then carry convergence lines back to their respective vanishing points."

Does this mean that you just guess the dimensions of the first square in 2-point? What about for 3-point?

prochristi86
04-12-2007, 11:00 PM
I thought of something else....

...what do you guys do for perpsective? Are there perspective grids out there that can be used in general, or do you just have to "tough it out"?

Scott Story
04-12-2007, 11:09 PM
David Chelsea's book had some sort of rule about there being a 90 degree angle at the bottom of the picture plane that leads to the vanishing points in 2D perspective. Check his book out.

There are books of perspective graphs available, but I find that more cumbersome than just drawing it.

Chelsea's book also had a cool method for figuring out circles in perspective, but again it was more trouble that it would usually be worth.

prochristi86
04-12-2007, 11:16 PM
Thanks Scott!

Hey, when you draw a scene in 3-point, how do you get an accurate box? In other words, how do you ensure that you have a perfect square, or; do you just estimate?

Scott Story
04-12-2007, 11:22 PM
OK, This is my understanding of it:

http://www.geocities.com/scottstory/promo/squaresville.gif

Put a square above any to lines from one of the vanishing points, and extend the width of the box down to hit those two lines.

These two point then go to the other vanishing point.

Extrapolate additional squares, for a tiled floore, for example, using the standard method.

Scott Story
04-12-2007, 11:37 PM
My understanding could be flawed, because I've done it so long I don't always remember how to put it into words, but this is my understanding of how to get a true sqare in perspective and how to extend squares in all directions based on that:

http://www.geocities.com/scottstory/promo/tilefloor.jpg

some of the perspective experts can probably point out if I'm wrong on this.

Now that I look at what I drew, it also looks as if you take the centerline through two of the lines from one perspective point, that you will also get true square in perspective, one that than can be extended in all directions.

prochristi86
04-13-2007, 01:53 PM
Wow!! Thanks a LOT, Scott! I see what you're doing... draw a perfect square, extend your verticals downwards until they collide with two lines (one from each of your two vanishing points) at arbitrary angles to the horizon... this will give you four points in space (on the floor) for your square... then extrapolate all other squares from this one.

Uh... I know you already know this.... I thought I'd just write it out to make sure I had it.

Now maybe I can figure out how to do this for 3-point...

TGK
04-13-2007, 02:06 PM
i had this book on perspective, the artist always draw a 45 degree angle line on the horizon line to get the perfect squares, I cant quite explain it but I can scan the page of book and show it to you if you want.

prochristi86
04-13-2007, 05:01 PM
Thanks TGK.... I appreciate it, but there's no need to -- this method Scott has explained will work for me. Thanks anyway! Now I've got to see if the same method will work for 3-point, or for the 3rd point. Any help here would be much appreciated.

prochristi86
04-14-2007, 08:15 PM
Sorry for double-posting again... I am not having any success finding out how to draw a perfect cube in 3 point perspective (well... Handprint (http://www.handprint.com/HP/WCL/perspect4.html) has a method, but it seems somewhat incomprehensible to me, and besides too complicated to use in general).

PLEASE tell me how you guys do it! :(

hellblazer72
04-17-2007, 10:33 PM
just draw your cube out in 2 point perspective but for the 2 sides use a vanishing point that lines up with the center line in your cube and that's either above or below your cube..these 2 lines will make up your sides...you might set up this 3rd vanishing about equal distance from one of your other points to the center line of your cube, so that you cube does not look distorted...hope this helps a little

prochristi86
04-19-2007, 01:11 PM
Thanks hellblazer72... this is a good technique, I think, but it still leaves us with an approximation of a cube. Is that what everyone usually does? Is it best to just guess the dimensions of your cube, or is it better to use another process (mind you--I have NO problems with guessing the cube's dimensions--but I need to know if that's what everyone else does, too)?

Thanks!

hellblazer72
04-19-2007, 10:13 PM
an example would be draw a center line four inches long, then from that line measure the same distance to the right and left..then just draw your lines from the 2 vanishing point for the top and bottom..then use the 3rd point to make up your sides...you'll then have a perfect 4 inch cube

prochristi86
04-21-2007, 11:42 AM
OK, is this what you mean?

http://www.coldfusiongames.com/perspective.jpg

If so, how do find length L (a green line)? Perhaps I misunderstood you, though...

Thanks for all the help!

hellblazer72
04-22-2007, 12:48 AM
that's what i mean..the green line in the middle would be what ever length you wanted the line to be..as for the sides there wouldn't be a way to pre measure them since they will be shorter due to the perspective...you can measure away from the center line to figure out where they sides will be but not how tall..

prochristi86
04-23-2007, 01:43 PM
Thanks for the help, hellblazer72! You see, that's the problem... I don't need to actually know how to measure the length of the green lines, but I *do* need to find out how everyone usually does it. Is the standard practice to simply estimate their length for your cube? Or is another method used?

hellblazer72
04-24-2007, 12:08 AM
i'm pretty sure that's the only method, i'm sure you might be able to pre measure them but your vanishing points would have to be quite far away to have your perspective lines match...i'm not sure you can get a perfect cube in 3 point perspective since the use of 3 point is to get a birds eye or worm's eye view-some kind of extreme perspective shot

bluelinesmoke
04-24-2007, 02:18 AM
Finding the length of the green lines is easy because they will follow your vanishing line. The difficult part is finding the right relationship between the green line, and the line that would be the base of the cube. I generally just eyeball it, partly because I'm lazy, and partly because I can usually get something that looks right anyway.

One big problem with that illustration is with an overhead view your third vanishing point would be beneath the cube as opposed to above. I very rarely use 3 point because it generally feels forced to me. In real perspective the third vanishing point is usually so far above or below the horizon that it's almost indistinguishable from a vertical line. Even when it is noticeable it should be subtle or it will give off a toon-town style forced perspective.

Siafu
04-24-2007, 10:35 AM
James, you're overanalyzing the use of a perfect 3 point cube man. There's no set way of doing it. Yeah most everyone uses the 3 vanishing points, convergence lines to make the sides (and or top and bottom depending on what perspective you're using) and just connect the lines from there.

If you take a photo of a city scape with a fish eye lens on a camera, you'll get this really cool looking curved image. Like looking through a fisheye hole in a door. That's 4 point perspective right there.

Many people will measure out every little line to make a 3 point cube. Others eyeball it. I think from what you've responded with from a lot of these examples... you know how to do it. Just do it. Like I said, there's no one perfect way to create it what you're looking for.

prochristi86
04-24-2007, 03:55 PM
THANKS....

bluelinesmoke: You're right that the relationship between the two is what's important, Siafu: Thanks, man. I'm SO glad to know that you can just eyeball it if you want to -- I'm pretty certain I can. After all, even the "technical" methods are still just approximation a cube--or that's how they're reffered to!

I ***FINALLY*** understand! :laugh:

prochristi86
04-24-2007, 05:20 PM
....I thought of something else:

Once you've established the horizon above the ground and know how high it is—say for example, your eye level is 5.75 feet—when you construct your square, how do you find the length of its sides (note that I am talking about the square ON THE FLOOR, not the vertical sides)? I mean, do you guess its dimensions as compared to the height of the eye level, or am I missing something here?

Siafu
04-24-2007, 09:05 PM
YOU'RE OVER ANALYSING!!! lol

Your length, width and height are all dependant on the convergence lines you draw from the vanishing points. If you want to measure out everything in incriments that's cool and all, but you're starting to take the fun out of your drawing. If you're drafting something or designing an engineering project then I can see being pricise, but if you're drawing comics or for fun, you're going too scientific on your approach.

prochristi86
04-25-2007, 12:12 AM
Lol, OK! :laugh: You're right.... I really appreciate the help. Now I can finally stop wasting hours staring at my pages trying to figure the perspective out!

:banana: (yay!)