Subject:
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Re: Free-Form Camera Positioning with MLCAD, L3P, and POV-RAY
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Newsgroups:
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lugnet.cad.ray, lugnet.cad.mlcad
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Date:
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Sat, 16 Dec 2000 16:22:02 GMT
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Viewed:
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5462 times
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Yes - It would be great to have a camera file. We would need a "lookat"
file as well.
Thanks again Michael for such an excellent piece of software. I have to say
that (besides LEGO), its one of the best toys I've ever had!
Brad
Michael Lachmann <michael.lachmann@lm-software.com> wrote in message
news:G5nCGp.GJ8@lugnet.com...
> I've never tried to use camera options until now, but I think we can • enhance
> that if we have a camera-file (like the light.dat) which L3P counts in. • This
> way it's easy to define the camera - position and orientation ...
>
> Regarding the description from the MLCad point of view it looks fine.
>
> Michael
> --
> ================================
> Ing Michael Lachmann
> Individual software development
> Tel.: +43 676 406 86 95
> e-mail: michael.lachmann@lm-software.com
> http: www.lm-software.com
>
> Brad Hamilton <bhamilto1@home.com> schrieb in im Newsbeitrag:
> G5L8sw.2Mp@lugnet.com...
> > Hi,
> >
> > This is a little write-up I did on free-form positioning of the camera. • It
> > is taken from several posts by myself and others on LUGNET. Tim • Courtney
> > has asked for new material for www.ldraw.org focusing on MLCAD, L3P and
> > POV-RAY, so I offered to write up a little blurb on camera positioning.
> > I'll incorporate people's ideas for about a week and then send Tim the • final
> > copy.
> >
> > If you could comment on any errors (content, spelling, or grammar), I'd
> > really appreciate it. Any additional suggestions would be great as • well.
> I
> > realize that there are other methods for camera positioning, but I felt • that
> > this one was simple and powerful.
> >
> > thanks
> >
> >
> >
> >
> > Free-Form Camera Positioning with MLCAD, L3P, and POV-RAY
> >
> > One of the hardest issues to grasp when starting out with MLCAD, L3P, • and
> > POV-RAY is figuring out how to position the camera to get the desired • shots.
> > Various techniques exist for camera positioning, but this article seeks • to
> > discuss one of the easiest and most powerful.
> >
> > Background
> > MLCAD describes 3D points using three different coordinates: (x,y,z). • If
> > you are looking at the front of a model, the X axis defines how far a • point
> > is to the left or right. The Y access defines how high a point is (i.e.
> > up/down). The Z access defines how far the point is away from the • viewer
> > (i.e. in and out). L3P converts these coordinates into a somewhat • different
> > system used by POV-RAY. The nice thing is that the reader need not
> > understand the POV-RAY system to position the camera.
> >
> > Finding a Point in MLCAD
> > A key to this technique is to locate the position of the camera and the
> > position of the "subject.' The subject is a point at which you want the
> > camera to point or "look at."
> >
> > To locate a point, load up the desired model in MLCAD. Typically, the
> > upper-left view shows the front. If it is set to something else, reset • it
> > to show the front. The lower-left view should show the model from • above.
> > Make sure this view is set to show the model from above..
> >
> > Now, move the cursor onto the upper-left view and position it where you
> > would like the camera to be. At the lower-left of the application • window
> > (in the status bar), MLCAD displays the coordinates of that point. You • can
> > only register two of the coordinates in any one view. Notice how the
> > coordinates change as you move the cursor. Write down the X and Y
> > coordinates based on the cursor position.
> >
> > Next, move the cursor onto the lower-left view, again where you want the
> > camera. This is necessary to get the third coordinate. When you've • found
> > the spot, write down the Z coordinate.
> >
> > Repeat this process to find a second point at which you want the camera • to
> > look. Often, the center of the model is an ideal spot.
> >
> > Keep MLCAD running while completing the rest of the process, as the
> > procedure can be repeated to find different camera locations.
> >
> > L3P
> > The L3P utility is used to generate a POV-RAY file from the MLCAD • output.
> > Although L3P supports some camera positioning options, this technique • doesn'
> > t use them. Just generate a POV-RAY file for your model using the • default
> > options.
> >
> > Using the Point in POV-RAY
> > Load up the POV-RAY file. Scroll down to the bottom of the text
> > representation of the file. Near the bottom, you will see something like • the
> > following:
> >
> > // Camera (Latitude,Longitude,Radius = 0,180,0)
> > camera {
> > #declare PCT = 0; // Percentage further away
> > #declare STEREO = 0; // Normal view
> > file://#declare STEREO = degrees(atan2(1,12))/2; // Left view
> > file://#declare STEREO = -degrees(atan2(1,12))/2; // Right view
> > location vaxis_rotate(<80,-600,-1400> + PCT/100.0*<0,0,3106>,
> > <0,-9.64724e+006,0>,STEREO)
> > sky -y
> > right -4/3*x
> > look_at <300,-150,0>
> > angle 40
> > rotate <0,1e-5,0> // Prevent gap between adjecent quads
> > file://orthographic
> > }
> >
> > It's not really necessary to understand the specifics of what this does.
> > You just need to plug in the appropriate values in the correct • locations.
> >
> > Put the three camera coordinates found earlier into the
> > ".vaxis_rotate(<X,Y,Z>.." construct.
> >
> > Put the three coordinates where you want the camera to point into the
> > "look_at<X,Y,Z>" construct.
> >
> > Now, save the file and do a test run. The procedure can be repeated • over
> > and over to refine the shot or to create new ones. It is not necessary • to
> > re-run the model through L3P each time. Just change the coordinates in • the
> > final POV-RAY file and re-run.
> >
> > Camera Lens
> > It is possible to simulate just about any camera lens. The zoom of the • lens
> > is controlled by the "angle" construct (see above). L3P generates a
> > standard view with this set to about 64. A telephoto lens (close-up • shot)
> > is simulated by a value of about 40. A wide-angle shot is simulated by • a
> > value of 100. Setting this to about 120 provides a super-wide-angle • shot
> > with some "fish-eye" effect.
> >
> > Doing a Photo Shoot
> > When doing many shots, it is often nice to save the camera positions. • This
> > is useful because you may want to enhance the model and then re-run the • same
> > series of shots. To do this, copy the above snippet from the POV-RAY • file
> > into a text file using notepad, Word, or any other editor. You can • comment
> > your shot by adding a line prior to it that starts with "//" • (slash-slash).
> > Then, when you want to re-run the shot, just copy the text from the text
> > file and replace that text block in the POV-RAY file.
> >
> >
> >
>
>
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