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 05:57:30 GMT
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Viewed:
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398 times
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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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