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From: [e-mail] (Justin Barrett)
Subject: Re: Morphing Curves
Date: Mon, 24 Jul 1995 14:56:00 GMT
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Organization: Ten Forward BBS in Port Angeles, WA 360.452.7681
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On 23 Jul 95, [e-mail] spoke up and said:

Ma>         I know that Lightwave morphs linear, but is there anyway to
Ma> morph a curve.
Ma>         I need to draw a few lines over a spinning globe to show
Ma> traveling routes.

Ma>         I have tried using a straight line that morphs to a curve, a
Ma> displacement map that displaces a straight line into a curved line.

Ma>         Any Ideas???

Here's one for you, using a combination of morphing and clip mapping.  I
take it you've been using actual objects (not maps) for the lines, so this
should work with the objects you currently have.  If not, it shouldn't be
too hard to do the modeling.

First, go into your favorite paint program and make a screen that has the
left side totally black, and the right side totally white...split EXACTLY
down the middle.  This exact half-and-half image is crucial to the effect
working properly.  Cut out a brush that is the full image width, and only a
few pixels high...5 would probably do.  This will become a moving clip map
to reveal your line.

Now to model the line.  First model the straight line version, or use the
straight line you already have.  You will need to have the end where the
line "begins" (where it will begin to be drawn or revealed) at 0,0,0, and
have it pointing in the positive X axis.  Give it a surface name of your
choosing, and save it.  Now bend and tweak it however you like into the
properly shaped curve, and save it as a separate object.

Now in Layout, load your two line objects.  Make a single clone of the
curved version.  Set the morph target of the straight line to the curved
line (1), morph value 100%, morph surfaces on.  Make *both* curved lines
100% dissolved.

Parent both curved lines to the straight line, and position the straight
line (now morphed) in its proper place by your globe.  Set a key at 0 for
all objects.

Now back in the objects panel, load the image you created earlier as a clip
map for the straight line.  Select Automatic sizing, and then reset the
texture center to 0,0,0 if it has been changed.  This texture setting
should place the center of the image map - the black/white crossover - at
the beginning end of your line, with the whole right side (+X) being
clipped by the white part of the image map.  Now take the X texture size
and triple it (at least).  Also, turn off pixel blending and anti-aliasing.

To reveal your line, set a positive X velocity for the clip map.  The black
part of the map will be "un-clipping" your object as it moves.  With a
high X size, there should be no danger of the map looping back onto itself
and re-clipping your beginning end.  Since the object is morphed, the
revealing process should follow your curved shape in a smooth, even
fashion.  You'll have to play with the velocity value to find a speed that
suits you.

When your line is completely revealed, do a one frame dissolve from curved
line (1) to curved line (2), which doesn't have the map affecting it.  Now
your line is fully visible, and will be as long as you need it.

Hope this works for you!

         Justin Barrett - [e-mail] - 1:350/401
    Free Spirit Productions   -   Northland Cable   -   Peninsula College

 * Q-Blue 2.1 *
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