CGTalk > WIP Measuring Accurate Proportins in a perspective drawing
 01-10-2005, 09:46 AM #1 Sanskrit New Member   Join Date: Sep 2004 Posts: 10 Measuring Accurate Proportins in a perspective drawing Hi! I would like to know how i could accurately measure proportions from a perspective drawing ? or how could i convert a perspective drawing into an orthographic drawing with accurate proportions ? I hope i have accurately framed this question and asked it in the right forum.I would greatly appreciate your comments.Thank you very much in advance. share quote
 01-11-2005, 02:39 AM #2 jmBoekestein likes a flower =)...   portfolio Jan Mark Boekestein Netherlands   Join Date: Nov 2004 Posts: 4,854 In my theorising I've found 2 problems with perspective drawing currentday. One is parallax, the actual effect with perception is that all straight lines are bent occurring to function which I willingly did not persue to calculate. I suspect it is something of a parallel to lens curvature and sensor region of image building/sampling. This effect can be best seen in wideangle lens photography. In todays drawings perspective is represented through drawing lines onto a vanishing point. It's a good fast solution and I don't mean one should not do that. Second; human error and nature. there's a looseness often in drawing which differ per artist. I find myself misinterpreting them often. Consequently I find myself asking for instance, why did he make it hollow instead of protruding like he drew it. This could easily happen to a perceiver that's not the artist him-/herself, and even to the artist himself applying techniques to approximate and suggest form instead of produce the exact requirement. this effect will be robably not so evident in photorealistic paintings and such, obviously. And in answer to your question, I suggest finding the vanishing points for corresponding objects drawn. Assingning one of them a scale, let's say 1,70 m=object=1. now from the extents that define the 1,70 m you draw towards the perspective vanishing points. you measure the deviation from that value in scale:(1=1,70m=objectA)*(1-deviation concluded) taking this and multiplying 1,70 with the outcome= true length. If the 2 objects are not parallel this is complicated to do but you can use the phythagoras system, I think, to interpolate. Since the perspective is inherently wrong, you are measuring an illusion. This is something best done by the human brain, lol. Check my 3d wip, as soon as I tested the eye curves for an actual eyeball geometry the flaw in the drawing came out; lol, she was apparently running 200 km/h and suddenly stopped when I took the picture. __________________ modelling practice #1 share quote
 01-11-2005, 01:38 PM #3 Sanskrit New Member   Join Date: Sep 2004 Posts: 10 Thank you so much jmBoekestein for your detailed explanation to my question.It certainly clarified my doubts. Your 3d wip looks great . I loved the concept art and the modelling is fabulous, its going to look amazing when you are done . share quote
 01-11-2005, 07:01 PM #4 jmBoekestein likes a flower =)...   portfolio Jan Mark Boekestein Netherlands   Join Date: Nov 2004 Posts: 4,854 Thanks Sanskrit, I'm very glad you like it! Hope to see some of your work soon. Good luck. __________________ modelling practice #1 share quote
 01-20-2006, 10:00 AM #5 CGTalk Moderation Expert   Join Date: Sep 2003 Posts: 1,066,478 Thread automatically closed 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. __________________ CGTalk Policy/Legalities Note that as CGTalk Members, you agree to the terms and conditions of using this website. share quote

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts vB code is On Smilies are On [IMG] code is On HTML code is Off CGSociety Society of Digital Artists www.cgsociety.org Powered by vBulletinCopyright ©2000 - 2006, Jelsoft Enterprises Ltd.