Subject:
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Re: Quick way to mirror-image a model?
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Newsgroups:
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lugnet.cad
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Date:
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Thu, 24 Jun 2004 15:09:39 GMT
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Viewed:
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4448 times
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In lugnet.cad, Carl Nelson wrote:
> What about a flag for default behavior? I've been coding to ignore
> ones with default rotations,
Why? I have a slow PC, and running the mirwiz.exe program is
nearly instantaneous. It's a lookup and 2 matrix multiplies per
part. If the exception matrix lookup fails, use the default matrix.
It would take extra, unneeded code to ignore things. Resist the
urge...
> but there are plenty of parts (especially slopes) that need a
> (-1 0 0 0 1 0 0 0 1) rotation
Stop saying rotation. It makes me think you're not doing it right.
That's a mirror matrix.
> applied when reflected front-to-back
> and it would be nice to have a flag to distinguish those needing
> default behavior from those where the true correction matrix is
> (-1 0 0 0 1 0 0 0 1).
If you *always* do the same matrix math there's no need to
distinguish. If you're not, then you're making extra busy work
for yourself and possibly introducing bugs. Here's the pseudo code.
for (*ALL* parts in the subfile)
{
float m[4][4]; // Tempory working matrix.
float md[4][4] = { // Default = left-right mirror
{-1.0,0.0,0.0,0.0},
{0.0,1.0,0.0,0.0},
{0.0,0.0,1.0,0.0},
{0.0,0.0,0.0,1.0}
};
float *me = md; // Init exception mirror to left-right (the default).
float *mp = md; // Init global subfile mirror to left-right.
for( i=0; i< numExceptions; i++ )
{
if (exception[i] matches this part)
{
// Use the matrix from the exception list (instead of md).
me = exception[i].matrix
// Also use the substitute partname
strcpy(datname, exception[i].datname);
break;
}
}
M4M4Mul(m,LinePtr->v,me); // Run the initial mirror on the part
M4M4Mul(LinePtr->v,mp,m); // Apply global subfile mirror to part
// NOTE: You can set mp to mirror across whatever plane you want.
// The example here mirrors the subfile across the YZ plane.
}
It's simple and it's all done with mirrors, except for a few weird
parts which might contain a rotation and/or translation component
mixed in with the mirroring in the me matrix.
So far I've only found a few door parts that need a translation
component. See http://ldglite.sf.net/mirror.ini for details on
the doors.
Enjoy,
Don
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Message has 1 Reply:
 | | Re: Quick way to mirror-image a model?
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| (...) Why process something as an exception when the default behavior is needed? It's all in what one sees as extra, unneeded code. ;-) Though I just did some timing and I don't see any performance differences between ignoring them and not. (...) (...) (20 years ago, 24-Jun-04, to lugnet.cad)
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Message is in Reply To:
| | Re: Quick way to mirror-image a model?
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| What about a flag for default behavior? I've been coding to ignore ones with default rotations, but there are plenty of parts (especially slopes) that need a (-1 0 0 0 1 0 0 0 1) rotation applied when reflected front-to-back and it would be nice to (...) (20 years ago, 24-Jun-04, to lugnet.cad)
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