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Subject: 
Re: How to obtain good photographs to make head patterns?
Newsgroups: 
lugnet.cad.dat.parts
Date: 
Sun, 20 Mar 2011 10:17:49 GMT
Viewed: 
35772 times
  
In lugnet.cad.dat.parts, Lee Gaiteri wrote:
> The technique I've been using to make minifig torsos can be extended to heads,
> but I have one critical problem that I haven't been able to figure out yet:
> Before tracing an image, I need an image that is facing the camera head-on.
> Normally to get a picture to trace, I just take an existing image and skew and
> stretch it into place so it's facing me directly. This really won't work for
> photos of heads, which have varying depth because they're mapped to a cylinder.
> 
> All I really need to make a patterned head is to have an image with an aspect of
> 26x16 (26 LDU wide, 16 high) that shows the face centered, and I can trace it
> and break it up into sections as needed to create the necessary shapes. (The
> image would probably need to be distorted first so the parts closer to the sides
> were stretched more.) I can find some photos online which I believe are too
> small to use easily, but they might be a good starting point if I can figure out
> how to correct for their perspective. Example here:
> 
> http://www.bricklink.com/PL/3626bpb271.jpg
> 
> Notice the face on the left is turned slightly on the Y axis, and the face on
> the right is turned even more. Both are pictured from an elevated position. Like
> most Bricklink photos I think the size is too small to use my technique on well,
> but if I find something with a higher resolution it will still need correction.
> 
> Is there any software that would help me correct the perspective in these kinds
> of photos so I can use them? The only alternatives I can think of are getting a
> better camera and taking my own photographs, painstakingly lining up each one,
> or else trying to write my own image distortion tool. Neither is a particularly
> exciting prospect.


Here are some ideas:

1. If you know the exact physical dimensions/characteristics of your digital
camera (focal length, aperture, diode size, etc.) I bet you can find a tool or
collection of algorithms online that you can use to convert the image into some
intermediary format.

2. POV-Ray is a good tool to "reverse-engineer" photographs IIRC. It requires
lots of technical knowledge however.

3. Locate and purchase an orthographic camera of some kind. As far as I am
aware, however, these only exist for industrial usage. So you may have trouble
finding one or affording it if you do happen to find one.


Those are the only ideas I could come up with.


-Mike



Message has 1 Reply:
  Re: How to obtain good photographs to make head patterns?
 
(...) FYI, it's called a "telecentric lens". Wikipedia: (URL) sure these are commonly available to the hobbyist market, though. -Mike (16 years ago, 22-Mar-11, to lugnet.cad.dat.parts)

Message is in Reply To:
  How to obtain good photographs to make head patterns?
 
The technique I've been using to make minifig torsos can be extended to heads, but I have one critical problem that I haven't been able to figure out yet: Before tracing an image, I need an image that is facing the camera head-on. Normally to get a (...) (16 years ago, 19-Mar-11, to lugnet.cad.dat.parts)

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