Distorted Android

///////////////////////////////////////////////////////////////////////////////////////////////////

// Copyright 2016 Leszek Koltunski                                                               //

//                                                                                               //

// This file is part of Distorted.                                                               //

//                                                                                               //

// Distorted is free software: you can redistribute it and/or modify                             //

// it under the terms of the GNU General Public License as published by                          //

// the Free Software Foundation, either version 2 of the License, or                             //

// (at your option) any later version.                                                           //

//                                                                                               //

// Distorted is distributed in the hope that it will be useful,                                  //

// but WITHOUT ANY WARRANTY; without even the implied warranty of                                //

// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the                                 //

// GNU General Public License for more details.                                                  //

//                                                                                               //

// You should have received a copy of the GNU General Public License                             //

// along with Distorted.  If not, see <http://www.gnu.org/licenses/>.                            //

///////////////////////////////////////////////////////////////////////////////////////////////////

package org.distorted.examples.flag;

import android.content.Context;

import android.opengl.GLSurfaceView;

import android.util.AttributeSet;

import android.view.MotionEvent;

///////////////////////////////////////////////////////////////////////////////////////////////////

class FlagSurfaceView extends GLSurfaceView

{

    private int mX, mY;

    private FlagRenderer mRenderer;

///////////////////////////////////////////////////////////////////////////////////////////////////

    public FlagSurfaceView(Context context, AttributeSet attrs)

      {

      super(context,attrs);

      mX = -1;

      mY = -1;

      if(!isInEditMode())

        {

        mRenderer = new FlagRenderer(this);

        setRenderer(mRenderer);

        }

      }

///////////////////////////////////////////////////////////////////////////////////////////////////

    public FlagRenderer getRenderer()

      {

      return mRenderer;

      }

///////////////////////////////////////////////////////////////////////////////////////////////////

    @Override public boolean onTouchEvent(MotionEvent event) 

      {

      int action = event.getAction();

      int x = (int)event.getX();

      int y = (int)event.getY();

      switch(action)

         {

         case MotionEvent.ACTION_DOWN: mX = x;

                                       mY = y;

                                       break;

         case MotionEvent.ACTION_MOVE: if( mX>=0 && mY>= 0 )

                                         {

                                         float px = mY-y;

                                         float py = mX-x;

                                         float pz = 0;

                                         float plen = (float)Math.sqrt(px*px + py*py + pz*pz);

                                         if( plen>0 )

                                           {

                                           px /= plen;

                                           py /= plen;

                                           pz /= plen;

                                           float cosA = (float)Math.cos(plen*3.14f/mRenderer.mScreenMin);

                                           float sinA = (float)Math.sqrt(1-cosA*cosA);

                                           mRenderer.mQuat1.set(px*sinA, py*sinA, pz*sinA, cosA);

                                           }

                                         }                             

                                       break;

         case MotionEvent.ACTION_UP  : mX = -1;

                                       mY = -1;

                                       float qx = mRenderer.mQuat1.getX();

                                       float qy = mRenderer.mQuat1.getY();

                                       float qz = mRenderer.mQuat1.getZ();

                                       float qw = mRenderer.mQuat1.getW();

                                       float rx = mRenderer.mQuat2.getX();

                                       float ry = mRenderer.mQuat2.getY();

                                       float rz = mRenderer.mQuat2.getZ();

                                       float rw = mRenderer.mQuat2.getW();

                                       // This is quaternion multiplication. (tx.ty.tz.tw)

                                       // is now equal to (qx,qy,qz,qw)*(rx,ry,rz,rw)

                                       float tx = rw*qx - rz*qy + ry*qz + rx*qw;

                                       float ty = rw*qy + rz*qx + ry*qw - rx*qz;

                                       float tz = rw*qz + rz*qw - ry*qx + rx*qy;

                                       float tw = rw*qw - rz*qz - ry*qy - rx*qx;

                                       // The point of this is so that there are always

                                       // exactly 2 quaternions: Quat1 representing the rotation

                                       // accumulating only since the last screen touch, and Quat2

                                       // which remembers the combined effect of all previous

                                       // swipes.

                                       // We cannot be accumulating an ever-growing list of quaternions

                                       // and add a new one every time user swipes the screen - there

                                       // is a limited number of slots in the EffectQueueMatrix!

                                       mRenderer.mQuat1.set(0f, 0f, 0f, 1f);

                                       mRenderer.mQuat2.set(tx, ty, tz, tw);

                                       break;

         }

      return true;

      }

}