Re: rotating the view volume

• To: Robert S Laramee <rlaramee@xxxxxxxxxxxxxx>
• Subject: Re: rotating the view volume
• From: Stuart Wier <wier@xxxxxxxxxxxxxxxx>
• Date: Thu, 08 Mar 2001 15:25:04 -0700

Robert 

Here is how I do something similar:

    private double [] pcMatrix;
    ProjectionControl projControl = localDisplay.getProjectionControl();
    pcMatrix = projControl.getMatrix();


    /**
     * Change point of view of a VisAD display, 
     * using user's input angles (unit = degree).
     * Preserves initial scaling and aspect ratios. View from
     * "southwest" has azimuth of 225 and decAngle say 45 or so.
     *
     * @param azimuth  azimuth from "north," clockwise, 0 to 360
     * @param decAngle tilt angle down from upward vertical. 0-180
     *
     */
    private void rotateView(double azimuth, double decAngle)
    {
        // trap input bad values? - not necessary since trig
        // functions handle values outside of 0-360 properly.
        // rotation around z axis, made from user's "azimuth"
        double zAngle = 180.0 - azimuth;
        try
            { 
                // rotate in z
                double [] aziMatrix = 
                    navDisplay.getDisplay().make_matrix
                    (0.0, 0.0, zAngle, 1.0, 0.0, 0.0, 0.0);
                double [] combo = navDisplay.getDisplay().multiply_matrix
                    (aziMatrix, pcMatrix);
                // rotate in x
                double [] decMatrix = navDisplay.getDisplay().make_matrix
                    (decAngle, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0);
                // total rotation matrix is computed and applied
                double [] combo2 = navDisplay.getDisplay().multiply_matrix
                    (decMatrix, combo);
                projControl.setMatrix(combo2); 
            }
        catch (Exception exp)
            {
                System.out.println("  rotate view got "+exp);
            }
    }

Stuart Wier                              UCAR Unidata Program
wier@xxxxxxxxxxxxxxxx                           P.O. Box 3000
http://www.unidata.ucar.edu/staff/wier      Boulder, CO 80307

• References:
  • rotating the view volume
    • From: Robert S Laramee