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geometrypointvector-graphics

Rotate array of points according one point

I have 4 points and angle (as shown on the picture). How to get new point values for rotated object?

picture(x/y axis inverted, mistake. Vertical should be Y, horizontal - X)

Solution

  • At first, get coordinates relative to the rotation origin (x0, y0)

    x' = x1 - x0
y' = y1 - y0

    Then rotate

    x'' = x' * Cos(Fi) - y' * Sin(Fi)
y'' = x' * Sin(Fi) + y' * Cos(Fi)

    And now shift coordinates back

    x_r = x'' + x0
y_r = y'' + y0