Math: Returning X,Y which is 150pixels @45degrees
BlitzMax Forums/BlitzMax Programming/Math: Returning X,Y which is 150pixels @45degrees
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| Hi all I'd like to know how to calculate the X, Y endpoint value which is nn-degrees from your current X,Y: StartX=140 StartY=340 TargetAngle: 136 degrees. DistanceToShoot: 235 pixels. using a circle a What will the X, Y value be? TIA! |
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| Is that what you need? TargetX = Sin(TargetAngle) * TargetDistance TargetY = -Cos(TargetAngle) * TargetDistance |
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| Fetze: You have that backwards. Might work, but this is the more traditional formula: X# = Radius# * Cos(Angle#) Y# = Radius# * Sin(Angle#) With that, angle 0 = right and angle 90 = down. So it goes clockwise from 3 o' clock. Unless you're doing 2D graphics in which case the Y axis is inverted, (positive is down instead of up) and so it goes counterclockwise instead. Or maybe I have that backwards. I think I might. Maybe it goes clockwise in 2D and counterclockwise in 3D.... Yeah I think that's what it does. So 90 would be straight up. |
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| I think yours is backward sswift, I would call 0 right and 90 up. and workit anti clockwise Each to their own i suppose |
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| On a 2D screen, 90 degrees will point down because the Y axis is inverted from standard euler coordinates. When dealing with 3D though, 90 degrees will point up. So if X = 50 and Y = 50 and you wanted to travel 100 pixels at a 45 degree angle, you'd end up at X = 121 and y = 121 (after rounding) which is below and to the right of the previous position. |
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| @sswift It works. Maybe not like you want your angle, but it works ^^ 0° --> up 90° --> right 180° --> down 270 --> left (On screen) |
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| For the most part, any combination of sin and cosine will work - it's just that the information you get will be relative to the method you use to get it. On the other hand, I'm sure there is a recommended standard. I'm assuming that cosine is used for the horizontal factor and sin for the vertical? |
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| BTW, i am doing this in 2D from a "top-down" view, no fancy physics or such stuff. TIA to everyone who contributes. BTW, isnt there in the Maths forum about the problem? |
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| pappavis, hasn't Fetze answered this? Did the suggestion work? That's what I would use. |
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| @Fetze: Yes, it works that way, but try converting an x,y value to an angle and rotation. The function Atan2(y,x) assumes you're using standard cartesian and polar coordinate systems inverted on the Y axis, which would be 0 right and 90 down. For consistency sake, it is best to use the same throughout. So from polar to cartesian" X = Cos(Angle#)*Distance# Y = Sin(Angle#)*Distance# and from cartesian to polar Angle# = Atan2(Y,X) 'Note that Y comes first Distance# = Sqr(X*X+Y*Y) |
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| Thanks to all who contributed to my question. The following code was the endresult.. Dont mind the c#-style comments. Look at the function GetXYforTargetAtAngle() down below in the code.
Type clsLijn
'/// <summary>
'/// Berken x/y koordinate van 'n doel, starten met jou huidige X/Y.
'/// </summary>
'/// <param name="StartX">Die gradehoek waarheen jy wil skiet</param>
'/// <param name="StartY"></param>
'/// <param name="intDistance"></param>
'/// <param name="dblTargetAngle"></param>
'/// <returns>een objek met x, y koordinaaten</returns>
Function GetXYforTargetAtAngle:clsLijnPos(StartX:Int, StartY:Int, intDistance:Int, dblTargetAngle:Int)
Local objXY1:clsLijnPos = New clsLijnPos;
objXY1 = clsLijnPos.Create();
'//normailseer die gradehoek, met cos en tan word die gradehoek oomgebuigd.
'//dblTargetAngle:-45;
If(dblTargetAngle < 45)
EndIf
Local dblRadians:Double = Self.GetNormaliseerNaarWareNoord(dblTargetAngle); '// normailseer naar ware noord in dit geval
Local dblX:Int = StartX + Int(intDistance * Sin(dblRadians * (Pi / 180)));
Local dblY:Int = StartY + Int(intDistance * Cos(dblRadians * (Pi / 180)));
objXY1.x = dblX;
objXY1.y = dblY;
Return objXY1;
End Function
EndType
Type clsLijnPos
Field x:Int;
Field y:Int;
Field IsNegativeSlope:Byte;
Function Create:clsLijnPos()
Local objLPos1:clsLijnPos = New clsLijnPos;
objLPos1.x = 0;
objLPos1.y = 0;
objLPos1.IsNegativeSlope = False;
Return objLPos1;
End Function
Function GetNormaliseerNaarWareNoord:Double(dblTargetAngle:Int)
Local dblRadians:Double = 0;
Try
dblRadians = (dblTargetAngle - 360) * (Pi / 180); '// normailseer naar ware noord in dit geval
Catch Err1:Object
Throw(Err1.ToString());
EndTry
Return dblRadians;
EndFunction
EndType
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