tease tricks 2004-01-23 - By Colin Holgate
Back
The rotation control of the vanes isn't that much different from
Greg's 2D sample script, only I didn't have to get into sine or Pi or
anything like that. Instead I did a variation of a simple bouncing
ball. With a ball falling under gravity, you start with a speed of
zero, and then each frame you add 1 to the speed, and then add the
speed to the vertical position. When the ball would have gone below
the ground you multiple the speed by -1, but continue to add 1 to the
speed (which will bring it back to zero when it peaks). To stop it
bouncing forever you multiply by something other than -1, hence the
.97 in Greg's example, or -.97 for the bouncing ball case.
For rotating something that needs to settle, you could do proper
pendulum mathematics, but a quick approximation is to do the same
speed trick as with the bouncing ball. In that case though you change
from adding 1 to adding -1 to the speed after the angle passes zero,
and multiply both the amount you're adding,and the speed by something
a bit below 1. I didn't that with trial and error until I liked the
look of it. The scripting is a bit ugly though, so I'll keep that
hidden!
The cute part of the movie though is the way the vanes are connected.
You can't just parent them together, because the rotation of the
second one would by the rotation of the first + the rotation of the
second. The third would be third+second+first, etc. To get a nice
effect would take a lot of adding and subtracting. Really you want
each vane to just have its own rotation to worry about. You also want
the rotation point to be at the top of the vane, if not a bit higher
than that.
The solution to the rotating outside of the model (there's probably
an easier solution to this part of the problem, but my solution helps
solve then next part too) is to have an invisible parent model and
translate the vane away from that (monospaced font used here):
0
__ ____ ____ ____ ____
| |
| |
|__ ____ ____ ____ ___|
The 0 is the invisible model, and by rotating that the child vane
part will swing nicely. That solves the swing vane part, but to solve
the connecting to the next vane I made another invisible model that
is also a child of the first invisible model:
0
__ ____ ____ ____ ____
| |
| |
|__ ____ ____ ____ ___|
@
The @ swings along with the vane. Now all that's needed is to set the
top invisible model to the location (but not rotation) of the
previous vane's bottom invisible model. The whole of this vane is
then pushed forwards, or backwards, or up or down, according to what
all the previous vanes are doing at the time.
The final effect looks good, even with the basic trick being simple!
http://staff.funnygarbage.com/colin/blinder.html
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<div>The rotation control of the vanes isn't that much different from
Greg's 2D sample script, only I didn't have to get into sine or Pi or
anything like that. Instead I did a variation of a simple bouncing
ball. With a ball falling under gravity, you start with a speed of
zero, and then each frame you add 1 to the speed, and then add the
speed to the vertical position. When the ball would have gone below
the ground you multiple the speed by -1, but continue to add 1 to the
speed (which will bring it back to zero when it peaks). To stop it
bouncing forever you multiply by something other than -1, hence the
.97 in Greg's example, or -.97 for the bouncing ball case.</div>
<div><br></div>
<div>For rotating something that needs to settle, you could do proper
pendulum mathematics, but a quick approximation is to do the same
speed trick as with the bouncing ball. In that case though you change
from adding 1 to adding -1 to the speed after the angle passes zero,
and multiply both the amount you're adding,and the speed by something
a bit below 1. I didn't that with trial and error until I liked the
look of it. The scripting is a bit ugly though, so I'll keep that
hidden!</div>
<div><br></div>
<div>The cute part of the movie though is the way the vanes are
connected. You can't just parent them together, because the rotation
of the second one would by the rotation of the first + the rotation of
the second. The third would be third+second+first, etc. To get a nice
effect would take a lot of adding and subtracting. Really you want
each vane to just have its own rotation to worry about. You also want
the rotation point to be at the top of the vane, if not a bit higher
than that.</div>
<div><br></div>
<div>The solution to the rotating outside of the model (there's
probably an easier solution to this part of the problem, but my
solution helps solve then next part too) is to have an invisible
parent model and translate the vane away from that (monospaced font
used here):</div>
<div><br></div>
<div><tt>
0</tt></div>
<div><tt>__ ____ ____ ____ ____</tt></div>
<div><tt
>| <span
></span>
|</tt></div>
<div><tt
>| <span
></span>
|</tt></div>
<div><tt>|__ ____ ____ ____ ___|</tt></div>
<div><br></div>
<div> The 0 is the invisible model, and by rotating that the
child vane part will swing nicely. That solves the swing vane part,
but to solve the connecting to the next vane I made another invisible
model that is also a child of the first invisible model:</div>
<div><br></div>
<div><tt>
0</tt></div>
<div><tt>__ ____ ____ ____ ____</tt></div>
<div><tt
>| <span
></span>
|</tt></div>
<div><tt
>| <span
></span>
|</tt></div>
<div><tt>|__ ____ ____ ____ ___|</tt></div>
<div><tt>
@</tt></div>
<div><tt><br></tt></div>
<div><tt><br></tt></div>
<div>The @ swings along with the vane. Now all that's needed is to set
the top invisible model to the location (but not rotation) of the
previous vane's bottom invisible model. The whole of this vane is then
pushed forwards, or backwards, or up or down, according to what all
the previous vanes are doing at the time.</div>
<div><br></div>
<div>The final effect looks good, even with the basic trick being
simple!</div>
<div><br></div>
<div>http://staff.funnygarbage.com/colin/blinder.html</div>
<div><br></div>
<div><br></div>
</body>
</html>
__ ____ ____ ____ ____ ____ ____ ____ ____ ____
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