Distorted Android

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

// Copyright 2020 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.library.mesh;

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

/**

 * Create a Mesh which approximates an equilateral triangle.

 */

public class MeshTriangles extends MeshBase

  {

  private static final float HEIGHT = (float)Math.sqrt(3)*0.5f;

  private int numVertices;

  private int remainingVert;

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

  private int addVertex(int vertex, float x, float y, float[] attribs)

     {

     remainingVert--;

     attribs[VERT_ATTRIBS*vertex + POS_ATTRIB  ] = x-0.5f;

     attribs[VERT_ATTRIBS*vertex + POS_ATTRIB+1] = y-HEIGHT/3;

     attribs[VERT_ATTRIBS*vertex + POS_ATTRIB+2] = 0.0f;

     attribs[VERT_ATTRIBS*vertex + NOR_ATTRIB  ] = 0.0f;

     attribs[VERT_ATTRIBS*vertex + NOR_ATTRIB+1] = 0.0f;

     attribs[VERT_ATTRIBS*vertex + NOR_ATTRIB+2] = 1.0f;

     attribs[VERT_ATTRIBS*vertex + INF_ATTRIB  ] = (x-0.5f);

     attribs[VERT_ATTRIBS*vertex + INF_ATTRIB+1] = (y-HEIGHT/3);

     attribs[VERT_ATTRIBS*vertex + INF_ATTRIB+2] = 0.01f   ;  // Inflated surface needs to be slightly in front

     attribs[VERT_ATTRIBS*vertex + TEX_ATTRIB  ] = x;

     attribs[VERT_ATTRIBS*vertex + TEX_ATTRIB+1] = y;

     return vertex+1;

     }

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

  private void computeNumberOfVertices(int level)

     {

     numVertices = level*(level+2);

     remainingVert = numVertices;

     }

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

  private int buildRow(int vertex,float sx, float sy, int length, float dx, float dy, float[] attribs)

    {

    for(int i=0; i<length; i++)

      {

      vertex = addVertex(vertex, sx   , sy   , attribs);

      vertex = addVertex(vertex, sx+dx, sy+dy, attribs);

      sx += 2*dx;

      }

    vertex = addVertex(vertex, sx, sy, attribs);

    return vertex;

    }

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

  private void buildGrid(float[] attribs, int level)

     {

     float sx = 0.0f;

     float sy = 0.0f;

     float dx = 0.5f/level;

     float dy = HEIGHT/level;

     int vertex = 0;

     for(int row=level; row>=1; row--)

       {

       vertex = buildRow(vertex,sx,sy,row,dx,dy,attribs);

       sx += 2*dx*(row-0.5f);

       sy += dy;

       dx *= -1;

       }

     }

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

// PUBLIC API

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

  /**

   * Creates the underlying grid of vertices with the usual attribs which approximates an equilateral

   * triangle.

   *

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

   */

  public MeshTriangles(int level)

     {

     super(1,HEIGHT,0);

     computeNumberOfVertices(level);

     float[] attribs= new float[VERT_ATTRIBS*numVertices];

     buildGrid(attribs,level);

     if( remainingVert!=0 )

       android.util.Log.d("MeshTriangles", "remainingVert " +remainingVert );

     setAttribs(attribs);

     }

  }