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rhythmone
03-01-2003, 10:28 PM
OK - I would like to be able to animate along a curve, so I am using the "attach to motion path".... I am choosing parametric "length" because I want to be able to write expressions and have the output be between 0 and 1 (basically to control where the object is along the path).

When I write my expression I get an error saying that it is already attached to an expression or setkey.... and I believe that this is because the motion path has the time connections.

When I "break connections" on this attribute it starts acting really wrong (sticky) and sometimes it stops moving along the path all together... almost like it starts to deteriorate because of the broken connections.
.... and to throw another variable into the mix, I am constantly I getting this warning:
// Warning: Cycle on 'addDoubleLinear1.output' may not evaluate as expected. (Use 'cycleCheck -e off' to disable this warning.) //
...of which I have posted about (along with a screenshot) in this thread:
http://www.cgtalk.com/showthread.php?s=&postid=437747#post437747


1 - Does anyone see a problem with breaking these connections
2 - Should I look at another approach since I do not plan to use the time connections anyway.
rhythmone
03-01-2003, 11:09 PM
One other question... Is the only way to "un" attach a motion path through the hypergraph?
lostpencil
03-02-2003, 01:30 AM
Hey Rhythmone,

I'm not sure if I can answer all your questions, but why not group the object to itself twice (creating two more translate nodes) and then attach the topmost group node to the path. That leaves the lower translate node to do with as you will. Does that help?
mattwood
03-02-2003, 10:56 AM
Hi Rythmone, first of all your logic for chosing "parametric" is wrong. I don't know the effect you're after but you almost certainly should be using uniform.

Next, breaking the connection is fine but it's easier to do it through the channel box. In the channel box you should be able to highlight the motion path node and see that the 'U value' attribute has a connection. Just right click on the attribute there and select 'break selected'

Finally, I suspect that the expression is the cause of the problems. If you have anything like 'x = x +1' it will give you unexpected results. Post your expression here and if there is a problem with it we'll tell you what it is.
rhythmone
03-04-2003, 04:27 PM
Thanks for both of your inputs.

My goal is basically to control an object along a path. I would like to use a percentage based value (i.e. 50% along path) because I could then scale the path and it would retain it's relative path placement.

why not group the object to itself twice (creating two more translate nodes) and then attach the topmost group node to the path

This is exactly what I am going for. I was just thrown off by the cycleCheck warning, and thought that I was doing something wrong.

breaking the connection is fine but it's easier to do it through the channel box.

Yeah, I did this and all seems to work fine.... my expression was really simple (basically motionPath1.u = motionPath2.u)..... it is all working now but I know there is somthing fishy going on in there, I had to restart Maya a few times.... I think it was the order in which I was connecting stuff because now it is OK.... I hope this doesn't come back to haunt me.....

first of all your logic for chosing "parametric" is wrong. I don't know the effect you're after but you almost certainly should be using uniform

I am going to look into this today.

My thanks to both of you.....
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