Magic Cube

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// Copyright 2020 Leszek Koltunski                                                               //

//                                                                                               //

// This file is part of Magic Cube.                                                              //

//                                                                                               //

// Magic Cube 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.                                                           //

//                                                                                               //

// Magic Cube 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 Magic Cube.  If not, see <http://www.gnu.org/licenses/>.                           //

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  private float[] mPoint, mCamera, mTouch;

  private float[][][] mCastAxis;

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  abstract boolean isInsideFace(float[] point);

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    mPoint = new float[3];

    mCamera= new float[3];

    mTouch = new float[3];

    mMove2D  = new float[2];

    mNumFaceAxis= mFaceAxis.length;

    mDistanceCenterFace2D = distance2D; // distance from the center of a face to its edge

    // mCastAxis[1][2]{0,1} are the 2D coords of the 2nd axis cast onto the face defined by the

    // 1st pair (axis,lr)

      mPoint[1]= a.get1();

      mPoint[2]= a.get2();

        {

        convertTo2Dcoords( mPoint, mFaceAxis[face], mCastAxis[face][casted]);

        normalize2D(mCastAxis[face][casted]);

        }

    }

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  private void normalize2D(float[] vect)

    {

    float len = (float)Math.sqrt(vect[0]*vect[0] + vect[1]*vect[1]);

    vect[0] /= len;

    vect[1] /= len;

    }

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// find the casted axis with which our move2D vector forms an angle closest to 90 deg.

    float cosAngle, minCosAngle = Float.MAX_VALUE;

    int minIndex=-1;

    float m0 = move2D[0];

    float m1 = move2D[1];

    float len = (float)Math.sqrt(m0*m0 + m1*m1);

    if( len!=0.0f )

      {

      m0 /= len;

      m1 /= len;

      }

    else

      {

      m0 = 1.0f;  // arbitrarily

      m1 = 0.0f;  //

      }

      y = mCastAxis[faceAxis][rotAxis][1];

      if( x*x + y*y > 0.01f )

        if( cosAngle<minCosAngle )

          {

          minCosAngle=cosAngle;

        }

      }

    return minIndex;

    }

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  private float computeOffset(float[] point, float[] axis)

    {

    return point[0]*axis[0] + point[1]*axis[1] + mDistanceCenterFace2D;

    return castCameraOnAxis > mDistanceCenterFace3D;

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// given precomputed mCamera and mPoint, respectively camera and touch point positions in ScreenSpace,

// compute point 'output[]' which:

// 1) lies on a face of the Object, i.e. surface defined by (axis, distance from (0,0,0)) [and this

//    distance is +-mDistanceCenterFace, depending if it is the face on the left or the right end of

//    the axis] (lr=0 or 1, so (2lr-1)*mDistanceCenterFace)

// 2) is co-linear with mCamera and mPoint

//

// output = camera + alpha*(point-camera), where alpha = [dist-axis*camera] / [axis*(point-camera)]

    float d0 = mPoint[0]-mCamera[0];

    float d1 = mPoint[1]-mCamera[1];

    float d2 = mPoint[2]-mCamera[2];

    float a1 = faceAxis.get1();

    float a2 = faceAxis.get2();

    float denom = a0*d0 + a1*d1 + a2*d2;

    if( denom != 0.0f )

      {

      float axisCam = a0*mCamera[0] + a1*mCamera[1] + a2*mCamera[2];

      output[0] = mCamera[0] + d0*alpha;

      output[1] = mCamera[1] + d1*alpha;

      output[2] = mCamera[2] + d2*alpha;

      }

    }

// Convert the 3D point3D into a 2D point on the same face surface, but in a different

// coordinate system: a in-plane 2D coord where the origin is in the point where the axis intersects

// the surface, and whose Y axis points 'north' i.e. is in the plane given by the 3D origin, the

// original 3D Y axis and our 2D in-plane origin.

// If those 3 points constitute a degenerate triangle which does not define a plane - which can only

// happen if axis is vertical (or in theory when 2D origin and 3D origin meet, but that would have to

// mean that the distance between the center of the Object and its faces is 0) - then we arbitrarily

// decide that 2D Y = (0,0,-1) in the North Pole and (0,0,1) in the South Pole)

    float a1 = faceAxis.get1();

    float a2 = faceAxis.get2();

    if( a0==0.0f && a2==0.0f )

      {

      y0=0; y1=0; y2=-a1;

      }

    else if( a1==0.0f )

      {

      y0=0; y1=1; y2=0;

      }

    else

      {

      float norm = (float)(-a1/Math.sqrt(1-a1*a1));

    float x1 = y2*a0 - y0*a2;  // (2D coord baseY) x (axis) = 2D coord baseX

    float x2 = y0*a1 - y1*a0;  //

    float originAlpha = point3D[0]*a0 + point3D[1]*a1 + point3D[2]*a2;

    float origin0 = originAlpha*a0; // coords of the point where axis

    float origin1 = originAlpha*a1; // intersects surface plane i.e.

    float origin2 = originAlpha*a2; // the origin of our 2D coord system

    float v0 = point3D[0] - origin0;

    float v1 = point3D[1] - origin1;

    float v2 = point3D[2] - origin2;

    output[0] = v0*x0 + v1*x1 + v2*x2;

    output[1] = v0*y0 + v1*y1 + v2*y2;

    }

// PUBLIC API

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  public boolean faceTouched(Static4D rotatedTouchPoint, Static4D rotatedCamera)

    {

    mPoint[1]  = rotatedTouchPoint.get1()/objectRatio;

    mPoint[2]  = rotatedTouchPoint.get2()/objectRatio;

    mCamera[0] = rotatedCamera.get0()/objectRatio;

    mCamera[1] = rotatedCamera.get1()/objectRatio;

    mCamera[2] = rotatedCamera.get2()/objectRatio;

        convertTo2Dcoords(mTouch, mFaceAxis[mLastTouchedAxis], mPoint2D);

        if( isInsideFace(mPoint2D) ) return true;

      }

    return false;

    }

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  public Static2D newRotation(Static4D rotatedTouchPoint)

    {

    mPoint[0] = rotatedTouchPoint.get0()/objectRatio;

    mPoint[1] = rotatedTouchPoint.get1()/objectRatio;

    mPoint[2] = rotatedTouchPoint.get2()/objectRatio;

    convertTo2Dcoords(mTouch, mFaceAxis[mLastTouchedAxis], mMove2D);

    mMove2D[0] -= mPoint2D[0];

    mMove2D[1] -= mPoint2D[1];

    float offset = computeOffset(mPoint2D, mCastAxis[mLastTouchedAxis][rotIndex]);

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  public int getTouchedFace()

    {

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