[Liser Studios]

hello
I was out in the backyard setting up stuff to make a 3 point pespective grid. I put some stakes into the ground and tied some fishing string onto it, and used that for marking the lines.
Well, I put the two side vanishing points down first. I had them 7 1/2 - 8 feet on each side... so it was about 16.5 feet wide from VP to VP.
Then I put down the other stake for the nadir (bottom VP). I put it further away from the paper than the side vanishing points... 8 feet 8 inches away from the bottom of the paper, 9 feet 11 inches from the horizon...
Ok... now... let's say I was doing the lines for the left vanishing point. I marked on the right side of the paper each an inch apart vertically, then drew the perspective lines for each marking.
I did that for all the rest.
Well, at the end, the grid didn't seem right. The perspective wasn't what I wanted, I wanted it to seem like I was looking down more... say... 90 is straight, 0 is straight down... I wanted 45. I got more like 70 or so. So, the nadir was too far away, I think.
But, the 2 point part just looked wrong. Did I put them too far apart? Should I not mark them an inch apart like that, maybe I should go by degrees or something? I don't know.
So... anyone got any ideas? How do you set up your perspective grids? Any trig/geometry/perspective masters know how far apart I should put everything to get the desired results?
Then I started reading about this "center of vision" which is in the middle of the triangle. Should I put my paper there? If I do, I wouldn't see the horizon in my drawing, and I want to!
i did the measurements (it's not to scale... but, ya know)

any input, suggestions, telling me I'm stupid for doing *this* and not doing *this*, would all be appreciated.

[ June 21, 2002: Message edited by: Liser Studios ]

[Ian Jones]

Well you don't need to have the two points exactly the same distance apart. You can have them off center by a long way. What is important is the angle that they create. You said it looked wrong, probably because of that angle, you have to judge with your eyes whether or not it is a right angle. That is a right angled flat grid viewed in perspective. See my point? Your perspective points can be fairly arbitrary so long as they relate to each other. If you were to place a square cardboard box in front of you, and angle it so that a diagonal points directly at you and directly opposite to your line of sight, then the birds eye view of your vanishing points would create a right angle fro your station point, where your eyes are. Remember I'm talking about viewing from a birds eye. The points would be equal distances from the center of vision, considering that the box was placed at 45 degree's. Get it? I know its hard to figure out, and I may not be totally right. I'm struggling with perspective myself.

Consider placing the box at a different angle as viewed from above. eg.. draw a vertical line to represent your line of sight. If you drew that same line in the perspective view it would recede directly away from you, and appear only as a dot. Talking of the birds eye view again... the bottom point of this line is your station point, where the eye is, then create an angle 30 degrees to the right side, and another line 60 degrees to the left side. 30 + 60 = 90 degrees.

When you then draw this in perpspective it would make your perspective box showing more of its left face, than its right.

I hope you understood that. Another variable to consider is that the closest point of the box doesnt have to be in line with the center of vision, your sight line. This is how you would draw another box to one side of the original one. If you placed the second box to be angled the same as the first, then its edges would be parallel with the first box. Meaning that it would share the same vanishing points.

Phew... I hope you got that. If not I'll have to make a drawing. Just ask.

[Liser Studios]

....i'm quite confused. Is there any way you can show me what you mean now? Seriously, if it takes a lot of time/trouble, don't do it.... I'm sure I'll eventually figure it out, eh?

[Ian Jones]

Yeah it would take a bit of time.. go and check out the Loomis thread.. goto that page, then look into the successful drawing book. It has a large section about perspective.

Recently I have been promising that I would make a comprehensive online tutorial. But I don't understand it all myself, so that will have to wait. Besides there's so many books already on the subject.