Away3D Forum ARC Math

Darcey, Moderator
Posted: 29 July 2011 10:25 AM Total Posts: 209

Anyone know how to Calculate the Y coordinate of an ARC based on a variable rotation.

Central Arc Angle = 140;
Arc Radius = 10;

Angle of rotation will flow through 0 to 140, so when rotation is at n I can get y (height) of arc at that time.

Result would be something like
0,0,0,0,00,1,2,3,4,5,6,7,8,9,10,9,8,7,6,5,4,3,2,1,0,0,0,0,0
depending on what rotation I am on.

Basically need the Y on the arc over time (rotating 3D object) only on 0 to 140 degrees of a circle.

Trying to do this with a single equation rather than multiple equations using an if to output this value from an equation that is not even related to arc but just for simple number sequence output.

H 70
H 35 105
H
H 0 140
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

I need the height (H) from X at 0 to 140 degrees.

Thanks

Darcey

Darcey, Moderator
Posted: 29 July 2011 11:01 AM Total Posts: 209 [ # 1 ]

http://www.allforthecode.co.uk/away3d/images/arc_attack.jpg

Darcey, Moderator
Posted: 29 July 2011 11:18 AM Total Posts: 209 [ # 2 ]

lol… No worries me over complicating things…

http://www.allforthecode.co.uk/away3d/images/simple.jpg

theMightyAtom, Sr. Member
Posted: 29 July 2011 11:28 AM Total Posts: 669 [ # 3 ]

All you need to do is plot the arc from -70 to 70 degrees.
To get the series to start at 0,0 just add an offset.

Something like:

this.addEventListener(Event.ENTER_FRAME,nextPos);
var angle:Number = -70;
var radius:Number = 10;

var startRadians:Number = -70 * (Math.PI / 180);
var startPosX:Number = Math.sin(startRadians) * radius;  
var startPosY:Number = Math.cos(startRadians) * radius;  

var radians:Number;
var xpos:Number;
var ypos:Number;

function nextPos(evt:Event):void{
 radians = angle * (Math.PI / 180); 
 xpos = (Math.sin(radians) * radius) - startPosX;
 ypos =  Math.cos(radians) * radius - startPosY;
 trace ( "xpos =" + xpos + " ypos=" + ypos); 
 angle++;
 
 if(angle > 70){
  this.removeEventListener(Event.ENTER_FRAME,nextPos);
 }
} 

Well, when I say something like, I mean “tested and working”

Darcey, Moderator
Posted: 29 July 2011 12:45 PM Total Posts: 209 [ # 4 ]

Will have a tinker with that thanks.

I think I will go down the route of manually entering:

1. Work out rotation range degrees min and degrees max (facing camera) using my visual debug class.

2. Correct degrees to limit at 360 so 358, 359, 0, 1, 2, 3

3. Offset the range to ensure a value of 0 to 140 degrees is always given

4. And work an if statement to give 0,1,2,3,4,5,4,3,2,1,0 based on if > 70

Especially since the planes vector (x,y,z) doesn’t change on the change of rotationY.

http://www.allforthecode.co.uk/away3d/arc_01/index.html.
The ARC Would be the green lines

ARC Math Software: Other

Darcey, Moderator Posted: 29 July 2011 10:25 AM Total Posts: 209 Anyone know how to Calculate the Y coordinate of an ARC based on a variable rotation. Central Arc Angle = 140; Arc Radius = 10; Angle of rotation will flow through 0 to 140, so when rotation is at n I can get y (height) of arc at that time. Result would be something like 0,0,0,0,00,1,2,3,4,5,6,7,8,9,10,9,8,7,6,5,4,3,2,1,0,0,0,0,0 depending on what rotation I am on. Basically need the Y on the arc over time (rotating 3D object) only on 0 to 140 degrees of a circle. Trying to do this with a single equation rather than multiple equations using an if to output this value from an equation that is not even related to arc but just for simple number sequence output. H 70 H 35 105 H H 0 140 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX I need the height (H) from X at 0 to 140 degrees. Thanks Darcey
Darcey, Moderator Posted: 29 July 2011 11:01 AM Total Posts: 209 [ # 1 ] http://www.allforthecode.co.uk/away3d/images/arc_attack.jpg
Darcey, Moderator Posted: 29 July 2011 11:18 AM Total Posts: 209 [ # 2 ] lol… No worries me over complicating things… http://www.allforthecode.co.uk/away3d/images/simple.jpg
theMightyAtom, Sr. Member Posted: 29 July 2011 11:28 AM Total Posts: 669 [ # 3 ] All you need to do is plot the arc from -70 to 70 degrees. To get the series to start at 0,0 just add an offset. Something like: this.addEventListener(Event.ENTER_FRAME,nextPos); var angle:Number = -70; var radius:Number = 10; var startRadians:Number = -70 * (Math.PI / 180); var startPosX:Number = Math.sin(startRadians) * radius; var startPosY:Number = Math.cos(startRadians) * radius; var radians:Number; var xpos:Number; var ypos:Number; function nextPos(evt:Event):void{ radians = angle * (Math.PI / 180); xpos = (Math.sin(radians) * radius) - startPosX; ypos = Math.cos(radians) * radius - startPosY; trace ( "xpos =" + xpos + " ypos=" + ypos); angle++; if(angle > 70){ this.removeEventListener(Event.ENTER_FRAME,nextPos); } } Well, when I say something like, I mean “tested and working”
Darcey, Moderator Posted: 29 July 2011 12:45 PM Total Posts: 209 [ # 4 ] Will have a tinker with that thanks. I think I will go down the route of manually entering: 1. Work out rotation range degrees min and degrees max (facing camera) using my visual debug class. 2. Correct degrees to limit at 360 so 358, 359, 0, 1, 2, 3 3. Offset the range to ensure a value of 0 to 140 degrees is always given 4. And work an if statement to give 0,1,2,3,4,5,4,3,2,1,0 based on if > 70 Especially since the planes vector (x,y,z) doesn’t change on the change of rotationY. http://www.allforthecode.co.uk/away3d/arc_01/index.html. The ARC Would be the green lines

ARC Math

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