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Subject: 
FAQqage: How to get zero perspective from L3P?
Newsgroups: 
lugnet.cad, lugnet.faq
Date: 
Tue, 28 Sep 1999 15:46:42 GMT
Reply-To: 
jsproat@io.SAYNOTOSPAMcom
Viewed: 
28 times
  
I think that's the right question.  I'm trying to get L3P to give me zero
skewing from perspective; I want an isometric view such as what LDraw gives
me.  I'm taking the approach that to do this in photography, you should get
real far back and zoom in.

So, I *think* it has to do with the radius field of the camera globe (-cg)
parameter; e.g. "p3" from:

-cg(p1),(p2)(p3)

...but when I try really high (~1000) or really low (~-1000) values, the
model renders into something really really small.  Values closer to zero
(~+-100) make a bigger image, but there's still some perspective.

Is there something I can hack inside the .POV file?

(*hack* *hack* *hack*)

Yes, there is.  I ran L3P with the -cg radius set to a really large number
(far from zero; I used 1000), and then I edited the .POV file, changing the
camera->angle (1) from 67.1234 to 5, effectively zooming in.  This value
tells POV-Ray how wide in degrees the viewport is, so a smaller number will
make stuff look larger.

I'll throw out some example code.

From the command prompt:

C:\LDRAW\MODELS>l3p -o -cg30,45,1000 somedat.dat

, which gives you the file SOMEDAT.POV .  Editing this file, the camera
object looks something like this:

// Camera (Latitude,Longitude,Radius = 30,45,1000)
camera {
// some stuff here
angle    67.3801
// some more stuff here
}

So, modify the angle value to something smaller:

angle    5

If you render a large picture from this, you'll still see some perspective.
I don't think you can completely get rid of it, but using a progressively
higher camera globe radius and a lower viewing angle will cause the effect
to become smaller and smaller.

Cheers,
- jsproat

1.  :-P How does one note member attributes for POV-Ray objects?!?

--
Jeremy H. Sproat <jsproat@io.com> ~~~ http://www.io.com/~jsproat/
"I've spent the past few years building up an immunity to bullets."
- Angus McGuire



Message has 3 Replies:
  Re: FAQqage: How to get zero perspective from L3P?
 
(...) This is very simple to achieve. You simply insert the "orthographic" statement inside the "camera" declaration. This will generate an image with the same perspective as LDLITE does, i.e., no perspective at all. Of course, you'll need to alter (...) (25 years ago, 28-Sep-99, to lugnet.cad, lugnet.faq)
  Re: FAQqage: How to get zero perspective from L3P?
 
Sproaticus: (...) There is a camera type for this. It should be enough to add "orthographic" at the beginning of the camera definition[1]. It could be fun, if the DAT Explorer switched to cylindrical projection so we could get to look all the way (...) (25 years ago, 28-Sep-99, to lugnet.cad, lugnet.faq)
  Re: FAQqage: How to get zero perspective from L3P?
 
(...) It's even easier than that. Just run C:\LDRAW\MODELS>l3p -o -cg30,45 -ca5 somedat.dat and L3P will automatically compute the radius for an angle of 5. I almost always change the camera angle to something between 30 and 50. (-ca30, -ca50) For (...) (25 years ago, 28-Sep-99, to lugnet.cad, lugnet.faq)

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