AVSIM MSFS Aircraft and Panel Design Forum


Key Frame Animation Basics

Posted by n4gix on Nov-15-02 at 10:10 AM In response to message #4

LAST EDITED ON Nov-15-02 AT 10:17 AM (EST)
 
Hi Steve!

I'm not going to comment on everything, but only a selection for which I have something (hopefully useful!) to say:

>Looking at the properties for objects, it appears that any
>object without a parent object is a child of the parent
>object (a virtual root object consisting of everything in
>the scene).

That is absolutely correct!

>This shows how objects are linked to one another. I was
>incorrect to say that I only used linked objects with
>keyframe animation. It helps to create a link between the
>parts of landing gear for two reasons. You need a link for
>any future keyframe animation for retractable landing gear.
>I assume you do not necessarily need a link for steerable
>gear. But it probably helps because all parts can steer
>without having to give them weird names (I have not created
>a steerable gear yet, but will have to for my a/c). I like
>to create a tree of objects just so I can see how they
>relate.

It is useful to think of 'linking' as if you were using Duco Cement to glue a plastic model together! Each part, when linked to a parent, becomes a part_of_that_part, as though you had 'glued' them together. When the parent is moved, the 'linked parts' will follow along and maintain the exact relative position to the parent they had when first linked... <simple, yes?>

For my steerable nosegear, I created and linked parts as follows:

c_gear_top
...c_gear_lower_piston
.....c_gear_lower_swingarm
.......c_gear_lower_swingarm_pin_top
.....c_gear_lower_swingarm_pin_bottom
.....c_gear_lower_swingarm_bracket
...c_wheel
.....c_gear_axle
.....c_gear_fork
.....c_tire
.....c_tire_still
.....c_spot_run...... just kidding here!
...c_gear_upper_swingarm
...c_gear_upper_swingarm_pin

For convenience, after through testing, I then grouped all the parts into one named group: <[nosegear>]

By doing this, I (a) have a visual indication that the assembly is complete! and - most importantly - uncluttered the 'pick list!'

As you can see from the above, relationships can be quite complex, but each parent-child sub-grouping is logically arranged to facilitate animation as a group, around a common axis!

BTW, "c_wheel" is a "dummy part" that I created (actually, it is a tiny little cube hidden inside the c_gear_fork part) to which the steering movement is applied. There are other ways of doing this, but this seemed the simplest in view of the other complex animations going on, such as the up/down compression of c_gear_lower_piston, the tire rotation, and the compound movements of the upper and lower swingarms.

>>the part name and parts with a numeric suffix are considered
>the same aircraft part. So l_flap is the same part as
>l_flap_7 and this implies to me they will all respond the
>same, i.e. be animated the same, which is not necessarily
>true, but a good guess and it turns out to be correct
>AFAIK.]

This is a very important point, because the improper use of 'stock animation names' can lead to some behavior which is undesired! (as several have already found out...)!

As you may note from the nosegear example above, all my parts begin with the same unique identification, c_gear_xxx such that when still ungrouped, they will all appear listed together in the alphabetical listing in the "Pick List."

However, we can't use that exact naming convention with 'stock animation names' without regard to the corresponding action that will be applied!

For example, if I had a 'hubcap' to add to c_tire_still, I could name it c_tire_still_hubcap, link it to c_tire_still and it would (a) spin in syncronicity with the tire, and (b) move in synchronicity with the tire during gear retraction.

Now, applying that same principle to a flap assembly, as you know in order to 'stock animate' the left flap you would simply tag the part with l_flap. However, if you have a bellcrank attached to the flap, you cannot name that part l_flap_bellcrank!!! Doing so will cause the bellcrank to move according to the axis point of l_flap, which is not what we want!

Instead, you could name the part l_flapbellcrank (which would preserve the convention mostly), so that the part is separated from the 'stock animation' and instead simply link that part as a child of l_flap. In effect, you have 'welded' that part to the flap assembly.

>I have not given my wings their dihedral yet. I am
>unfamiliar with how the dihedral is applied to a wing. I
>hope that I can just angle the wings up a bit (the dihedral
>is small, about 1.7 etc.). Thanks for reminding me to set
>the pivot angle to match (and I suppose all the wing parts
>like aileron, flap, trim will have to match).

After you have set all the pivot points properly for your wing assembly, move the pivot point for the wing to the center of rotation (i.e, the root of the wing at the central axis of the a/c!), select all the parts that make up that wing, and use the rotation tool to angle the entire wing assembly to the correct dihedral angle. All of the existing defined pivot points for flaps, ailerons, etc. will maintain their existing relationship with respect to the wing!

I hope that this helps someone, somewhere!



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