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Programming a natural looking swing (was Repulsion between physical and other objects)
by AnnMarie@SLFBI
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It is a long time since I did one and mine was a vertical motion but from
memory, here is an outline on how to go about it.
The program has two segments. The first to generate a list of numbers that
runs only if you change swing parameters.
This list of numbers is used by the second program segment that moves the
swing.
For the first part that generates the data list:-
You decide how many steps you want to do from peak to peak on the swing.
This can be user-setable if you want to adjust smoothness.
Divide 180 degrees by this number to get the step angle for looking up.
Start at 90 degrees and step to -90 degrees (converted to radians) and look
up the llSin() of these angles and put them in a list.
This will give you a list of numbers starting at +1 and ending at -1.
You now step through this list to create a second list.
You need to scale and convert the numbers from +1 through -1 to an angle for
llSetRot().
So +1 will correspond to the highest point on the swing, say 35 degrees
(which can be user adjustable too).
zero will correspond to swing vertical
-1 corresponds to swing back 35 degrees, all converted to radians.
You run this segment as needed to create the working list that contains the
angles that are plugged into llSetRot() only on rez, or when user wants to
change one of the parameters.
To run the swing have it sit at half way through the list (vertical) if you
want it to be able to stop.
When it starts, step through the list using a timer set to total swing time
divided by the number of steps (can be user adjustable).
You will be stepping from mid point on the list to the bottom, then reverse
and step through to the top, then reverse again.
On each step put the list angle value into llSetRot().
Although it is not physical, there is some smoothing built into llSetRot()
changes, they don't move instantaneoulsy so experiment to find the minimum
number of steps that looks smooth and reduces computing overhead.
If you want to get REALLY fancy, you can let the swing accelerate/decelerate
on start/stop by changing the 35 degree angle in increasing/decreasing steps
from/to zero, recalculating the angle list each time.
I'm sure the above could be written to calculate the angles on the fly
instead of using the list look-up but I did it this way. It is easier to
understand and is probably less processing load on the sim computer.
AnnMarie Otoole.
----- Original Message -----
From: "G" <gcanaday@...>
To: <secondlifescripters@...>
Sent: Thursday, September 04, 2008 11:22 AM
Subject: Re: Repulsion between physical and other objects
>
> Ann,
>
> oo? How does that work? /me looks for example...
>
> G
>
_______________________________________________
Click here to unsubscribe or manage your list subscription:
https://lists.secondlife.com/cgi-bin/mailman/listinfo/secondlifescripters
memory, here is an outline on how to go about it.
The program has two segments. The first to generate a list of numbers that
runs only if you change swing parameters.
This list of numbers is used by the second program segment that moves the
swing.
For the first part that generates the data list:-
You decide how many steps you want to do from peak to peak on the swing.
This can be user-setable if you want to adjust smoothness.
Divide 180 degrees by this number to get the step angle for looking up.
Start at 90 degrees and step to -90 degrees (converted to radians) and look
up the llSin() of these angles and put them in a list.
This will give you a list of numbers starting at +1 and ending at -1.
You now step through this list to create a second list.
You need to scale and convert the numbers from +1 through -1 to an angle for
llSetRot().
So +1 will correspond to the highest point on the swing, say 35 degrees
(which can be user adjustable too).
zero will correspond to swing vertical
-1 corresponds to swing back 35 degrees, all converted to radians.
You run this segment as needed to create the working list that contains the
angles that are plugged into llSetRot() only on rez, or when user wants to
change one of the parameters.
To run the swing have it sit at half way through the list (vertical) if you
want it to be able to stop.
When it starts, step through the list using a timer set to total swing time
divided by the number of steps (can be user adjustable).
You will be stepping from mid point on the list to the bottom, then reverse
and step through to the top, then reverse again.
On each step put the list angle value into llSetRot().
Although it is not physical, there is some smoothing built into llSetRot()
changes, they don't move instantaneoulsy so experiment to find the minimum
number of steps that looks smooth and reduces computing overhead.
If you want to get REALLY fancy, you can let the swing accelerate/decelerate
on start/stop by changing the 35 degree angle in increasing/decreasing steps
from/to zero, recalculating the angle list each time.
I'm sure the above could be written to calculate the angles on the fly
instead of using the list look-up but I did it this way. It is easier to
understand and is probably less processing load on the sim computer.
AnnMarie Otoole.
----- Original Message -----
From: "G" <gcanaday@...>
To: <secondlifescripters@...>
Sent: Thursday, September 04, 2008 11:22 AM
Subject: Re: Repulsion between physical and other objects
>
> Ann,
>
> oo? How does that work? /me looks for example...
>
> G
>
_______________________________________________
Click here to unsubscribe or manage your list subscription:
https://lists.secondlife.com/cgi-bin/mailman/listinfo/secondlifescripters
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