View Full Version : need a little help with perspective cube
rattsang 08102006, 08:02 PM http://img85.imageshack.us/img85/5584/perbyrattsangul4.jpg
hi there ive been studying perspective and none of the books ive read show how to do this so im wondering if its possible and if so how to do it.
it the above pic. the green dots marked vp1 and vp2 are the two vanishing points for a cube with its cornor facing out towards the viewer. by drawing the solid red line to establish the middle (cornor) and connecting to the vanishing points i can easily determine the hight of the cube as it diminishes into the distance. however now im stuck, the dotted red lines are estimations of where i think the cube ends for thoese faces. is there any method fo exactly calculating the distance of these lines from the middle cornor so it makes a perfect cube? i am completely stumped  please help
rat


spnhead
08112006, 06:27 AM
Get this book:
The Theory and Practice of Perspective (http://djm.cc/library/Theory_Practice_Perspective_Storey_edited.pdf)
This is the best book on perspective that I've seen.
spnhead
rattsang
08112006, 10:13 AM
sorry that book does not help i need an answer to the specific question only
thanks
rat
Hmm, would like to know how to do it myself. One workaround for the problem would be to project a square onto the "floor" and use it as the base of your cube in 3D, don't remember how exactly that was done, though, but I'm sure you can google it up.
DeathArtist
08172006, 10:41 PM
Back in Grade 7 or 8, our teacher taught us to draw the object first then draw circle diagonally from the object that you have drawn. Draw a cube then draw a dot diagonally from the cube then connect the cube's points to the dot. I hope that helps.
Just Call Me Bruce!
08182006, 03:43 AM
You have to project the box down, like this:
http://forums.cgsociety.org/attachment.php?attachmentid=100198&stc=1
(if the image doesn't show up sorry it's my first time putting an image in)
edit: hope this helps you^^
p.s. If you don't get it, i copied it from a book i have so maybe i can explain it for you if need be.
rattsang
08182006, 09:53 AM
Back in Grade 7 or 8, our teacher taught us to draw the object first then draw circle diagonally from the object that you have drawn. Draw a cube then draw a dot diagonally from the cube then connect the cube's points to the dot. I hope that helps.
hi deathartist that isnt very clear could you post an image and explain each line that is in it.
just call me bruce, i know this method and it isnt very accurate and causes masssive distorsion as you can probably see from your pic thanks anyway.
thanks
rat
Just Call Me Bruce!
08182006, 04:05 PM
maybe something like a dimetric projection (http://en.wikipedia.org/wiki/Axonometric_projection). if not matbe you could be a little more specific, like what you need if for?
wormee
08212006, 12:18 AM
Get this book:
The Theory and Practice of Perspective (http://djm.cc/library/Theory_Practice_Perspective_Storey_edited.pdf)
This is the best book on perspective that I've seen.
spnhead
Thank you so much for this link!
I cannot stop reading, and I am sure it will be a great deal of help for my future drawings.
cheers
//edit:
After some reading I think it might even answer the OP's question. Look for pages 3053 in the book.
BigSky
08222006, 08:58 AM
Your intuition was right. Your cube is correct, you just have a very "wide angle" lens. The positioning of your vanishing points determines this.
CGTalk Moderation
08222006, 08:58 AM
This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum.
vBulletin v3.0.5, Copyright ©20002014, Jelsoft Enterprises Ltd.