Re: Wave op offset

[Joey Ponthieux <j.g.ponthieux(at)LaRC.NASA.GOV>]

I think what you are looking at here is a bug. You can replicate it's 
behavior by doing the following.

In XSI 5.11

1. Create a grid in a new scene, assign it 24x24 subdivisions. Scene 
should be the default 1-100 frames.
2. Create a wave, with grid selected, Model:Get>Primitive>Control Op>Wave.
3. Lock the Wave property page so that it will remain on screen.
4. Play the timeline, the grid should wave from 1-100 and stop at 100.
5. In the Explorer navigate to grid/Polygon Mesh/Wave Op, open the Wave 
Op and lock the page.
6. Open the animation editor via right-click WaveOp/Amplitude>Animation 
editor
7. In the Wave Op Time Control tab, type in 50 for start. Take note that 
the ampl curve in the animation editor changes. Also note that the ampl 
starts at 49.51, not 50 as you would expect.
9. Now type in 10000 for the End value in Time Control. Hit the Enter 
key. Notice in the Animation
Editor that the start value has changed once again, now to -45.61 or 
some other bizarre number and
is still not 50 as you would expect. The larger the End value to the 
more pronounced the error is.
Worse yet sometimes the End value will take and other times it won't.

Subsequent modifications to the Start offset and End value in Time 
Control further corrupt the apparent association which ampl has with the 
Time Control. Apparently you can still edit ampl's keys but this 
behavior does seem to suggest that there is something wrong in the Wave 
Op(as opposed to the Wave) setup. Basically you have to set the wave 
start and end by modifying ampl manually, the Time Control does not 
appear to work as expected.

The best way to manually assigning starting times to the wave is just 
delete the basic animation which comes with Amplitude in Wave Op, go to 
the frame you want it to start, key at zero, go to the frame you want it 
to be in full force, key at 1. Likewise with the end just do it in 
reverse 1-0. To script this would probably require some sort of driven 
key or at least an expression that starts at 0 for the frame you define 
and ramps upward using time or frame as the multiplier until it caps out 
at 1.

Note: do not delete the Spread animation, as for some reason this causes 
the wave to just quit, regardless Spread's resting value. It apparently 
has to have at least one key present to maintain persistence.



Joey Ponthieux
NCI Information Systems Inc.
NASA Langley research Center
____________________________________________________________
Opinions stated here-in are strictly those of the author and
do not represent the opinions of NASA or any other party.



Mathieu Leclaire wrote:
> Hum, this thing is starting to give me a headache. I'm trying to deform a
> mesh with some wave ops. The problem is that I want them to start at
> different frames. So if I create a wave object I put the Periodicity in time
> which gives me a nice ring that start at the center of the wave and spreads
> out which is all nice. But what if I want it to start at a later frame? In
> the Wave Op there is a time start offset but although that makes the wave
> appear at the right frame, the wave is already spread out at the same
> position that it would have had if it started at the first frame. The only
> way I found to make it work is by translating the wave amplitude profile
> keys but I don't see the relation between the numbers on the graph and the
> frame number. Now I don’t want to move them by hand until I find the right
> position because I want to apply them by script and I can't find out how to
> make them start at the desired frame using scripting. Can anyone help me
> figure this thing out?
>
> Thanks.
>
>
> Mathieu Leclaire
> R&D Programmer
> Hybride Technologies
>
>
>
>
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