Yet another blog about WPF, Surface, SL, MVVM, NUI.... - Tag - calculation - Comments

How to scale around a specific point and not the center of the Element - Martin Berger

Martin Berger — Fri, 07 Dec 2012 10:20:03 +0100

Hello,

what is this last line supposed to perform?

   if (scaleDelta > 1.0)
       _myObjectToScale.Center += new  Vector(newCenterXD, newCenterYD);
   else
       _myObjectToScale.Center += new  Vector(newCenterXD, newCenterYD);

scaleDelta can be less or greater that 1.0, same code will execute.

Calculate the real difference between two angles, keeping the correct sign - AlexL

AlexL — Mon, 22 Oct 2012 00:06:35 +0200

Thanks, this helped me out big time!

Calculate the real difference between two angles, keeping the correct sign - JonathanANTOINE@falsemail.com

JonathanANTOINE@falsemail.com — Fri, 06 Apr 2012 09:02:50 +0200

Cool !

Calculate the real difference between two angles, keeping the correct sign - tigrou

tigrou — Thu, 12 Jan 2012 13:18:30 +0100

Perfect ! just what i was looking for. Tested and works successfully !

Calculate the real difference between two angles, keeping the correct sign - RNH

RNH — Wed, 04 May 2011 04:31:45 +0200

If you only want to know the absolute difference then you can use
DEL = PI - ABS(PI - ABS(A - B)) in radians.
DEL = 180 - ABS(180- ABS(A - B)) in degrees.

Calculate the real difference between two angles, keeping the correct sign - marco polo

marco polo — Thu, 28 Apr 2011 22:09:55 +0200

try this..

      private static double GetPositiveAngle(double radian)
       {
           if (radian < 0)
               radian = (Math.PI * 2) - Math.Abs(radian);
           return radian;
       }

       public static double GetAngleDifference(double angle1, double angle2)
       {
           var rslt1 = GetPositiveAngle(angle1);
           var rslt2 = GetPositiveAngle(angle2);
           if (rslt2 < rslt1)
               rslt2 += 2 * Math.PI;
           return rslt2 - rslt1;
       }

Calculate the real difference between two angles, keeping the correct sign - AronT

AronT — Sun, 24 Apr 2011 16:42:33 +0200

A snippet of code taken from my archive in Blitz3D that was used to turn a missile towards the player

It eliminates the need to use mod
Will work with angles of any size
Returns an angle in the range -180 to 180
(
diffangle = (actualangle - destangle) + 180;
diffangle = (diffangle / 360.0)
diffangle = ((diffangle - Floor( diffangle )) * 360.0) - 180;
)
!Notes: The Floor command takes the float number and rounds it down to the nearest whole number!

Calculate the real difference between two angles, keeping the correct sign - Alan

Alan — Fri, 08 Apr 2011 12:09:28 +0200

I use:

differenceAngle = (targetAngle - currentAngle) % 360.

this gives you the angle of the target relative to current angle, and is positive for a clockwise rotation.

How to scale around a specific point and not the center of the Element - Jonathan ANTOINE

Jonathan ANTOINE — Sat, 05 Jun 2010 17:16:00 +0200

@Jack A:Hello, You may put the IsHitTestVisible property to false ?

How to scale around a specific point and not the center of the Element - Jack A

Jack A — Sat, 05 Jun 2010 14:19:27 +0200

This is a really great article.

I would like to be able to prevent a scatterviewitem from continuing to manipulate after I have removed all contacts from it. In other words I would like to prevent an item from being thrown across the screen, but simply want it to stop at my last point of contact. None of the scatterviewitem methods, properties and events seem to offer this capability. Do you know if this is possible?

Calculate the real difference between two angles, keeping the correct sign - René

René — Tue, 27 Apr 2010 15:55:23 +0200

@Rich

350 - 10 = 340 > 180 => 340 - 360 = -20

Calculate the real difference between two angles, keeping the correct sign - Rich

Rich — Mon, 29 Mar 2010 21:02:10 +0200

@tk is superior as the sign can interpret the direction of rotation. Jon's method doesn't work in some cases, say 10 degrees to 350 reports 20 degree turn, not -20 degree...

Calculate the real difference between two angles, keeping the correct sign - Liz

Liz — Fri, 22 Jan 2010 11:17:52 +0100

@tk : That's so elegant - thank you, just what I needed :o)

Calculate the real difference between two angles, keeping the correct sign - Jonathan ANTOINE

Jonathan ANTOINE — Sat, 28 Nov 2009 23:49:29 +0100

@tk :I simply do it to have the right result : the angle can be more than 360° (suppose you have done 2 turns)....

Your solution may works too...

Calculate the real difference between two angles, keeping the correct sign - tk

tk — Sat, 28 Nov 2009 22:40:40 +0100

I was wondering two things: why do you use while instead of if, is that C#? and, perhaps, could you do
double difference = mod( secondAngle - firstAngle + 180, 360 ) - 180;
I suppose it depends on the compiler or deeper knowledge of the computer to know which is faster.

Calculate the real difference between two angles, keeping the correct sign - Aubrey

Aubrey — Sat, 07 Nov 2009 12:43:34 +0100

Yep. We use this where I work (and in my homebrew). We call it "Normalize180", and there's a variant called "Normalize360", which does the same thing, but in the range 0f<a<360f.

You could also divide the difference by 180.0f, then take only the fractional part of that (behind the '.' ) and multiply it by 180, making sure to maintain the sign.

i.e.
float NormalizedAngle = diff / 180.0f;
if(diff > 0){
return (NormalizedAngle - Math.Floor(NormalizedAngle)) * 180.0f;
} else {
return (( NormalizedAngle - ( Math.Floor(NormalizedAngle) + 1.0f ) * 180.0f );//Errr... not sure about this bit - have to deal with negative case. Might be a better way to get the fractional part than number minus floor(number)
}

That would probably be less cycles than a while loop, but typical input numbers are unlikely to be high, so your approach is probably fine in most cases.

[ping] How to scale around a specific point and not the center of the Element - DotNetShoutout

DotNetShoutout — Sun, 11 Oct 2009 18:37:02 +0200

How to scale around a specific point and not the center of

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[ping] How to scale around a specific point and not the center of the Element - DotNetKicks.com

DotNetKicks.com — Sun, 11 Oct 2009 18:22:13 +0200

How to scale around a specific point and not the center of

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Calculate the real difference between two angles, keeping the correct sign - Peter

Peter — Sun, 04 Oct 2009 21:21:30 +0200

You saved my day

Calculate the real difference between two angles, keeping the correct sign - Jonathan ANTOINE

Jonathan ANTOINE — Thu, 18 Jun 2009 17:03:56 +0200

@[Dan] : The angles can ve really more than 360 and it will then works with this code.
Also I don't think using a while instead of an if cause a lot of perf problems...