blitz-research
85 lines
2.1 KiB
HTML
85 lines
2.1 KiB
HTML
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<title>Blitz3D Docs</title>
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<link rel=stylesheet href=../css/commands.css type=text/css>
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<h1>ATan2# ( y#, x# )</h1>
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<h1>Parameters</h1>
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y, x are any numbers.
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They are interpreted as corresponding to a point ( x, y ).
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<h1>Description</h1>
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ATan2 gives the angle between the positive x-axis and a vector from the point (0,0) to the point (x,y).
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One common use is in 2d graphics. Suppose you have two objects and you want to aim the first at the second.
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ATan2( y2 - y1, x2 - x1 ) gives the proper orientation for object1.
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You can use this angle to select an appropriately rotated image.
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Notice the reverse order, ATan2( y, x ) rather than ATan2( x, y).
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ATan2( y, x ) is analogous to ATan( y / x), but covers 360 degrees.
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The angle satisfies: -180 < ATan2 <= +180
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<h1><a href=../2d_examples/ATan2.bb>Example</a></h1>
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; ATan2 example.
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; Move mouse. Escape quits.
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Const width = 640, height = 480
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Const radius# = .2 * height
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Const KEY_ESC = 1
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Graphics width, height
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SetBuffer BackBuffer( )
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Origin width / 2, height / 2
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HidePointer
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MoveMouse .75 * width, height / 2
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While Not KeyDown( KEY_ESC )
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Cls
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Color 255, 255, 0
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Line 0, 0, width / 2, 0 ; positive x-axis
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x = MouseX() - width / 2
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y = MouseY() - height / 2
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Oval x - 3, y - 3, 7, 7, True
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Line 0, 0, x, y
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Text .35 * width, -80, "x = " + x
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Text .35 * width, -60, "y = " + y
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Text .35 * width - 96, -40, "ATan2( y, x ) = " + ATan2( y, x )
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Flip
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Wend
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End
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<a target=_top href=../index.htm>Index</a><br>
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Click <a href=http://www.blitzbasic.co.nz/b3ddocs/command.php?name=ATan2&ref=comments target=_blank>here</a> to view the latest version of this page online</body>
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</html>
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