3 point perspective

[l.e.b]

I hope this is the right place to put this thread!
Ive been trying to master 3 point perspective but the position of the third point still confuses me. The two points from 2point lie on the same line, i guess you can put them any distance apart you want. When i put a 3rd point in (i just guess this and try i different distance and spacing each time) I can make a nice looking cube!
Then i go for making another nice cube, further away from the first, but the lines from the 3rd point make it look as if viewed through a fish eye lens, or in beserk mode in doom 3
Now i read some artistic cats can draw the 3rd point not even on the paper, HOW i ask. Wouldnt you need like a point for every cube you make?
If i did plot a point far enough to produce realistic proportions, wouldn't i have to plot out the points on a huge piece of paper, use a massive ruler and just end up drawing on a small section?
Is it not possible to create say a picture of a city or something without making it look like its built on a really small planet? Im not sure how describe it eh but its difficult

[Infinitum]

You do have to have the third point quite far awayy i'm afraid. That dosn't mean you need a hugh piece of paper though. Just put a small dot of blu tak or something on your desk and use that. It usually works well to have all the points off the paper actualy to make it look realistic.

I hope this helps.

[madster]

The T3 area is more for "answers," than "questions."
This thread is moved to Fine Arts, Studies & Discovery, "The technical side to art."

~M

[taxman]

I hope this is the right place to put this thread!
Ive been trying to master 3 point perspective but the position of the third point still confuses me. The two points from 2point lie on the same line, i guess you can put them any distance apart you want. When i put a 3rd point in (i just guess this and try i different distance and spacing each time) I can make a nice looking cube!

There is NO guessing where vanishing points are, not in 1, 2 nor in 3 point systems. I´ve drawn the process of setting up a 3 point system for you, hope this helps. :)

http://tinypic.com/e5mr6s.jpg

http://tinypic.com/e5mrn9.jpg

http://tinypic.com/e5mruq.jpg

http://tinypic.com/e5ms01.jpg

http://tinypic.com/e5ms7m.jpg

http://tinypic.com/e5mscy.j[pg

You should know, that perspective systems only work in a certain area around your main point of view (in this case, the POV is right inside the cube). If you move too far away from this area, the distortion gets too big. I think this is what causes your problem.

I can give you a more detailed explanation if you want, but I have to find a dictionary with technical terms first I guess... :(

[ravindranak]

i was on my terrace yesterday wonder ing how to draw these cars below ....all the while i was trying to put it in 2 point perspective ...
didnt think about the 3 point thing ...
thanks ...

[l.e.b]

ty taxman you are star
i saved that although i would be lying if i said i understood it

[taxman]

Ok I.e.b., I found a dictionary with technical terms now, so I try to explain what´s going on in these pictures. But please, forgive me my crappy English. :(

pic 1:
Mark the position of the observer (St). Then, draw a floor plan of the cube you intend to represent with a 3 point system. We know that the floor plan of a cube is a square. :)

Next, add the image plane by drawing a horizontal line. The distance between the position of the observer and the image plane determines the size of the cube in perspective, but has no effect on it´s distortion.

Draw the horizon line. You can basically draw it anywhere you want, the cube will automatically be in the right position in relation to the horizon line later. Add a vertical line through the position of the observer that is perpendicular to the horizon line and the line of the image plane.

Now we can construct vanishing points 1 & 2 by drawing parallels to our floor plan of the cube through the position of the observer. Notice where these parallels intersect with the line of the image plane: If you mark these points on your horizon line, you have successfully constructed vanishing points 1 & 2.
Yikes!

pic 2:

Project the four corners of the square into the image plane. Mark the points where they intersect the line of the image plane on the horizon.

pic 3:

Drop in another vertical line (anywhere you want; Yikes! I´m starting to sound like Bob Ross. :D ) and meassure the distance between St (point of the observer) and the line of the image plane with a ruler. Mark this distance on the horizon on the left side and drop in another vertical line ( this works on the right side as well but I don´t want to get too confusing; you can simply flip the image in photoshop to see what I mean).
Now project the outside corners of our little square from the floor plan to the first vertical line, then to the line of the image plane by using three parrallel lines. Just look at the picture. :)

pic 4:

In this step we draw the sheer plan of our cube. Note where the vertical line on the left intersects with the horizon. This is where the eye of a (one-eyed)
observer would be. And don´t get confused: In my example, this point is very close to vanishing point 1, but that´s just coincidence.
In this example I´ve drawn a cube from above, so we draw the ground line below the horizon. You can experiment what happens when you move the ground line up and down.
Now draw the sheer plan of the cube. We have already determined the two vertical contours in step three, the height of the cube equals the side of the square in the floor plan.

pic 5:

Find the middle of the cube in the sheer plan and draw a line from the point where the eye of our (one eyed) observer would be through the middle of the cube in the sheer plan. This line is the direction of our view. Imagine Cyclops from the X-Men standing there shooting a laser beam to destroy the cube. :teeth:

Then, we drop in the image plane in the sheer plan: It intersects the horizon line where the second vertical line (the one a bit left from the middle ) intersects the horizon and is perpendicular to Cyclops laserbeam. Note where our image plane intersects the vertical line on the left: If we stick a geometry compass in the intersection of our vertical line in the middle and the horizon and rotate this point to the vertical line in the middle and then use a parallel line to the horizon to elongate it to the vertical line on the right side (aaaaargh, this is really confusing I guess; but it doesn´t have to be, just look at the picture), we have found vanishing point 3. Wohoo!

All we have to do now is to determine the height of our cube. As we already know all three vanishing points and the directions the verticals will have (the four points we marked in step 2), we project the left vertical of the sheer plan (which equals the vertical of the cube that´s next to the observer) from the eye of our observer on the image plane, then rotate and elongate like we have done in the construction of vanishing point 3.

pic 6

Draw the cube. There is no guessing at all, we have everything worked out in step 5. :)

Hope this helps... :blahblah:

[max1975]

Taxman: I haven't quite figured out your drawings yet, but your English is excellent.