Motion path question

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Old 12 December 2004   #1
Motion path question

Hi,
Don't know if this as been addressed before but here goes. How do you get an object to follow a pre-defined path and follow the path orientation? I've searched the documents and can't find anything on doing this.
Thanks,
Francois
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Old 12 December 2004   #2
You need a curve and either the 'MoveToCurveParam/MoveToCurveLength' or the 'AlignToCurveParam/AlignToCurveLength' expressions.

The 'MoveTo...' expressions constrain an object to a curve, while the 'AlignTo...' expressions also align the object. For some reasons the 'AlignTo...' expressions can't be found in the documents, but they are in the expression list. Contrary to the description there, the forth parameter is the fader of the position constraint of the object and the fifth parameter is the position of the imaginary target.

Look at the sample file, the 'Path' slider determines the position of the object along the path.
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Old 12 December 2004   #3
thanks, will try that
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Old 12 December 2004   #4
tried to open your sample file in messiah and it does not work
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Old 12 December 2004   #5
Hmm, that's strange, the MPJ file opens fine here ... Anyway, that's what I did in the scene:

1. Created a curve with some points.
2. Added a procedural cube.
3. Added a slider with a channel called 'Path'
4 In the 'Command' tab I added the expression

AlignToCurveParam(Curve,Cube,[Slider:chan[Path]],0,[Slider:chan[Path]]+0.1,0)
 


Moving the slider animates the cube along the spline. The third value in the expression is the position along the spline (0 = beginning of spline, 1 = end of spline), the fifth parameter is the position of the imaginary target, i.e in my example the cube looks ahead by 1/10 of the curve length.
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Old 12 December 2004   #6
Suricate,
I really appreciate your help
Somehow the file had no extension and when I tried to put the mpj extension, messiah did not recognize it. Tried the sample you describe and it works. I want to animate a vehicle following a path along a terrain that is not flat. How can I import a curve derived from the terrain into messiah and convert it to a messiah curve?

Thanks,
Francois
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Old 12 December 2004   #7
you can also use the flexmotion effect. just add that to the root object, and translate it along Z. it will follow your path.
 
Old 12 December 2004   #8
Stiderotte, do you mean e.g. you have modeled the terrain and now want to make the vehicle follow the road ? I think there is no automated way to import an object and make a curve out of it, but if you are using LW as your modeling app, there is a plug-in (I think) that converts the points of an LWO model to nulls in Layout. This LWS scene can be read by messiah and then you can use the nulls for reference for your curve. This is a bit tedious if there are many points to add, but I don't know of any other way.
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Christopher Lutz
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Old 01 January 2006   #9
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