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Help With A Math Rotation Problem
Infrared Wind
Gridologist
Join date: 7 Jan 2007
Posts: 662
08-09-2007 22:47
Hi -

If anyone can help with this math rotation problem it would be great.

Here's the problem:

I'm making a humidity gauge with a rotating arrow based on RL weather
numbers. Using llHTTPRequest/http_response I assign a float number
to a variable, for example: "34.4".

The dial graphic background was created in a graphics program, so the
ticks are not perfect, but they're essentially 2.7 degrees apart around
the dial. .

To point at O% humidity on the dial the arrow (a stretched cube) is
turned 231 degrees on the Y axes. To point at 100% humidity the arrow is
turned to 140 degrees on the Y axes. 50% is at 4 degrees on the Y axes.

So the way I've got it working so far is this:

I assign the http_response to a var:

float n1 = (integer)n;

Then I have a long list of if clauses, which I've only bothered
to assign whole numbers so far:

if(n1 == 0) n1 = 231.0;
if(n1 == 2) n1 = 236.4;
if(n1 == 3) n1 = 239.1;
if(n1 == 4) n1 = 241.8;

...etc...

if(n1 == 97) n1 = 130.9;
if(n1 == 98) n1 = 133.6;
if(n1 == 99) n1 = 136.3;

...etc...

And then...

rotation hand_rot = llEuler2Rot(<1 * n1 * DEG_TO_RAD, 0, 0>;);

This works...but there must be a better way; a way to derive the range of
SL Y axes degrees from the float numbers mathematically instead of
foolishly with a calculator manually as I have done.

Well...if anyone knows what the hell I'm talking about and can
offer some light...I'd be stoked!

- Infrared
Strife Onizuka
Moonchild
Join date: 3 Mar 2004
Posts: 5,887
08-10-2007 02:28
Try:
CODE

//humidity should be in the range [0.0, 100.0]
rotation hand_rot = llEuler2Rot(<(231.0 + humidity * 0.027) * DEG_TO_RAD, 0, 0>);
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Infrared Wind
Gridologist
Join date: 7 Jan 2007
Posts: 662
08-10-2007 03:14
From: Strife Onizuka
Try:
CODE

//humidity should be in the range [0.0, 100.0]
rotation hand_rot = llEuler2Rot(<(231.0 + humidity * 0.027) * DEG_TO_RAD, 0, 0>);


Whoa...you're the man! =)

That's exactly what I was looking for. I just needed a bit of direction.
After playing I found this to do what I wanted:

rotation hand_rot = llEuler2Rot(<1 * (230.0 + humidity * 2.72) * DEG_TO_RAD, 0, 0>;);

SWEET...thank you, Strife. I'm stoked!

- Infrared