3D Engine for Dummies - Page 15

The Rotations (con't)

Now we are going to do the buttons:

• open your first button (say the up-rotation around the x-axis). Enter this

  On (Roll Over)
        Set Variable: "sin" = -  basesin
        Set Variable: "cos" = basecos
        Set Variable: "axis" = "x"
  End On
  On (Release, Roll Out)
        Set Variable: "axis" = "none"
  End On

  The sign of the sine determines which direction the object turns. When you roll over the button, the axis turned around is set to x, and the sin and cos are stored. When you roll out, the axis is set to none. The principle is the same for all the other buttons, but with different values.
• x-axis down rotation

        Set Variable: "sin" =  basesin
        Set Variable: "cos" = basecos
        Set Variable: "axis" = "x"

• y-axis right-rotation

        Set Variable: "sin" = - basesin
        Set Variable: "cos" = basecos
        Set Variable: "axis" = "y"

• y-axis left-rotation

        Set Variable: "sin" = - basesin
        Set Variable: "cos" = basecos
        Set Variable: "axis" = "y"

• z-axis rotation(1)

        Set Variable: "sin" = - basesin
        Set Variable: "cos" = basecos
        Set Variable: "axis" = "z"

• z-axis rotation(2)

        Set Variable: "sin" = basesin
        Set Variable: "cos" = basecos
        Set Variable: "axis" = "z"

The last thing we have to do to make our rotation functional is obviously to program the rot frames. This is a simple use of the math-formulas. Open the rotx frame and enter this

Set Variable: "n" = "1"
Loop While (n<=totalpoints)
      Set Variable: "tmp" = (sin * eval("y"&n)) + ( cos * eval("z"&n))
      Set Variable: "y"&n = cos * eval("y"&n) - sin * eval("z"&n)
      Set Variable: "z"&n = tmp
      Set Variable: "n" = n + 1
End Loop

Set Variable: "n" = "1"
Loop While (n<=totalpoints)
      Set Variable: "tmp" = - (sin * eval("x"&n)) + ( cos * eval("z"&n))
      Set Variable: "x"&n = cos * eval("x"&n) + sin * eval("z"&n)
      Set Variable: "z"&n = tmp
      Set Variable: "n" = n + 1
End Loop

Set Variable: "n" = "1"
Loop While (n<=totalpoints)
      Set Variable: "tmp" = (sin * eval("x"&n)) + ( cos * eval("y"&n))
      Set Variable: "x"&n = cos * eval("x"&n) - sin * eval("y"&n)
      Set Variable: "y"&n = tmp
      Set Variable: "n" = n + 1
End Loop