Distorted Android

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// Copyright 2018 Leszek Koltunski                                                               //

//                                                                                               //

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

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

//                                                                                               //

// 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                             //

package org.distorted.library.mesh;

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

/**

 * Create a Mesh which approximates a sphere.

 * <p>

 * of its 8 faces vertically split into 2 triangles, and which each step divide each of its triangular

 * faces into smaller and smaller subtriangles and inflate their vertices to lay on the surface or the

 * sphere.

public class MeshSphere extends MeshBase

  {

  // longitude of V3 is simply midpoint of V1 and V2 so we don't have to specify it here.

      { 0.00*P, 0.25*P, 0.0, 0.5*P },

      { 0.25*P, 0.50*P, 0.0, 0.5*P },

      { 0.50*P, 0.75*P, 0.0, 0.5*P },

      { 0.75*P, 1.00*P, 0.0, 0.5*P },

      { 1.00*P, 1.25*P, 0.0, 0.5*P },

      { 1.25*P, 1.50*P, 0.0, 0.5*P },

      { 1.50*P, 1.75*P, 0.0, 0.5*P },

      { 1.75*P, 0.00*P, 0.0, 0.5*P },

      { 0.00*P, 0.25*P, 0.0,-0.5*P },

      { 0.25*P, 0.50*P, 0.0,-0.5*P },

      { 0.50*P, 0.75*P, 0.0,-0.5*P },

      { 0.75*P, 1.00*P, 0.0,-0.5*P },

      { 1.00*P, 1.25*P, 0.0,-0.5*P },

      { 1.25*P, 1.50*P, 0.0,-0.5*P },

      { 1.50*P, 1.75*P, 0.0,-0.5*P },

      { 1.75*P, 0.00*P, 0.0,-0.5*P },

  private int currentVert;

  private int numVertices;

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

// plus 2 extra vertices to start off a row and 2 to move to the next row (or the next face in case

// of the last row) and there are 'level' rows.

  private void computeNumberOfVertices(int level)

    {

    }

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

    if( currentVert>0 )

      {

      attribs1[VERT1_ATTRIBS*currentVert + POS_ATTRIB+1] = attribs1[VERT1_ATTRIBS*(currentVert-1) + POS_ATTRIB+1];

      attribs1[VERT1_ATTRIBS*currentVert + POS_ATTRIB+2] = attribs1[VERT1_ATTRIBS*(currentVert-1) + POS_ATTRIB+2];

      attribs1[VERT1_ATTRIBS*currentVert + NOR_ATTRIB+1] = attribs1[VERT1_ATTRIBS*(currentVert-1) + NOR_ATTRIB+1];

      attribs1[VERT1_ATTRIBS*currentVert + NOR_ATTRIB+2] = attribs1[VERT1_ATTRIBS*(currentVert-1) + NOR_ATTRIB+2];

      attribs1[VERT1_ATTRIBS*currentVert + INF_ATTRIB+1] = attribs1[VERT1_ATTRIBS*(currentVert-1) + INF_ATTRIB+1];

      attribs1[VERT1_ATTRIBS*currentVert + INF_ATTRIB+2] = attribs1[VERT1_ATTRIBS*(currentVert-1) + INF_ATTRIB+2];

      attribs2[VERT2_ATTRIBS*currentVert + TEX_ATTRIB+1] = attribs2[VERT2_ATTRIBS*(currentVert-1) + TEX_ATTRIB+1];

      currentVert++;

      }

    }

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

// Supposed to return the latitude of the point between two points on the sphere with latitudes

// lat1 and lat2, so if for example quot=0.2, then it will return the latitude of something 20%

// along the way from lat1 to lat2.

//

// This is approximation only - in general it is of course not true that the midpoint of two points

// on a unit sphere with spherical coords (A1,B1) and (A2,B2) is ( (A1+A2)/2, (B1+B2)/2 ) - take

// (0,0) and (PI, epsilon) as a counterexample.

//

// Here however, the latitudes we are interested at are the latitudes of the vertices of a regular

// icosahedron - i.e. +=A and +=PI/2, whose longitudes are close, and we don't really care if the

// split into smaller triangles is exact.

//

// quot better be between 0.0 and 1.0.

// this is 'directed' i.e. from lat1 to lat2.

  private double midLatitude(double lat1, double lat2, double quot)

    {

    return lat1*(1.0-quot)+lat2*quot;

    }

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

// Same in case of longitude. This is for our needs exact, because we are ever only calling this with

// two longitudes of two vertices with the same latitude. Additional problem: things can wrap around

// the circle.

// this is 'undirected' i.e. we don't assume from lon1 to lon2 - just along the smaller arc joining

// lon1 to lon2.

  private double midLongitude(double lon1, double lon2, double quot)

    {

    double min, max;

    if( lon1<lon2 ) { min=lon1; max=lon2; }

    else            { min=lon2; max=lon1; }

    double diff = max-min;

    if( diff>P ) { diff=2*P-diff; min=max; }

    double ret = min+quot*diff;

    if( ret>=2*P ) ret-=2*P;

    return ret;

    }

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

// linear map (column,row, level):

//

// (      0,       0, level) -> (lonV1,latV12)

// (      0, level-1, level) -> (lonV3,latV3 )

// (level-1,       0, level) -> (lonV2,latV12)

    double quotY = (double)row   /level;

      {

      quotZ = quotX + 0.5*quotY;

      }

    else                      // polar triangle

      {

    double latitude  = midLatitude(latV12, latV3, quotY );

    double cosLON = Math.cos(longitude);

    double sinLAT = Math.sin(latitude);

    double cosLAT = Math.cos(latitude);

    float y = (float)(sinLAT        / 2.0f);

    float z = (float)(cosLAT*cosLON / 2.0f);

    double texX = 0.5 + longitude/(2*P);

    if( texX>=1.0 ) texX-=1.0;

    double texY = 0.5 + latitude/P;

    attribs1[VERT1_ATTRIBS*currentVert + POS_ATTRIB+1] = y;  //

    attribs1[VERT1_ATTRIBS*currentVert + POS_ATTRIB+2] = z;  //

                                                             //  In case of this Mesh so it happens that

    attribs1[VERT1_ATTRIBS*currentVert + NOR_ATTRIB  ] = 2*x;//  the vertex coords, normal vector, and

    attribs1[VERT1_ATTRIBS*currentVert + NOR_ATTRIB+1] = 2*y;//  inflate vector have identical (x,y,z).

    attribs1[VERT1_ATTRIBS*currentVert + NOR_ATTRIB+2] = 2*z;//

                                                             //  TODO: think about some more efficient

    attribs1[VERT1_ATTRIBS*currentVert + INF_ATTRIB  ] = x;  //  representation.

    attribs1[VERT1_ATTRIBS*currentVert + INF_ATTRIB+1] = y;  //

    attribs1[VERT1_ATTRIBS*currentVert + INF_ATTRIB+2] = z;  //

    attribs2[VERT2_ATTRIBS*currentVert + TEX_ATTRIB  ] = (float)texX;

    attribs2[VERT2_ATTRIBS*currentVert + TEX_ATTRIB+1] = (float)texY;

    currentVert++;

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

    // Problem: on the 'change of date' line in the back of the sphere, some triangles see texX

    // the whole texture there. Solution: remap texX to 1.0.

      double tex2 = attribs2[VERT2_ATTRIBS*(currentVert-3) + TEX_ATTRIB];

      if( tex1!=tex2 && tex1>0.5 )

      }

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

    for(int row=0; row<level; row++)

      {

      for (int column=0; column<level-row; column++)

        {

        if (column==0 && !(face==0 && row==0 ) ) repeatVertex(attribs1, attribs2);

        addVertex(attribs1, attribs2, column, row+1, level, lonV1, lonV2, latV12, latV3);

      if( row!=level-1 || face!=NUMFACES-1 ) repeatVertex(attribs1, attribs2);

    }

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

// PUBLIC API

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

  /**

   * Creates the underlying grid of vertices with the usual attribs which approximates a sphere.

   * <p>

   * When level=1, it outputs the 12 vertices of a regular icosahedron.

   * When level=N, it divides each of the 20 icosaherdon's triangular faces into N^2 smaller triangles

   * (by dividing each side into N equal segments) and 'inflates' the internal vertices so that they

   * touch the sphere.

   *

   * @param level Specifies the approximation level. Valid values: level ≥ 1

   */

  public MeshSphere(int level)

    {

    float[] attribs2= new float[VERT2_ATTRIBS*numVertices];

    for(int face=0; face<NUMFACES; face++ )

      {

    if( currentVert!=numVertices )

      android.util.Log.d("MeshSphere", "currentVert= " +currentVert+" numVertices="+numVertices );

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

/**

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

/**

 *

 * @param deep If to be a deep or shallow copy of mVertAttribs1, i.e. the array holding vertices,

 *             normals and inflates (the rest, in particular the mVertAttribs2 containing texture

 *             coordinates and effect assocciations, is always deep copied)