content: /*
   * Copyright (C) 2007 The Android Open Source Project
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package android.opengl;
  
  /**
   * A collection of utility methods for computing the visibility of triangle
   * meshes.
   *
   */
  public class Visibility {
      /**
       * Test whether a given triangle mesh is visible on the screen. The mesh
       * is specified as an indexed triangle list.
       *
       * @param ws the world space to screen space transform matrix, as an OpenGL
       * column matrix.
       * @param wsOffset an index into the ws array where the data starts.
       * @param positions the vertex positions (x, y, z).
       * @param positionsOffset the index in the positions array where the data
       *        starts.
       * @param indices the indices of the triangle list. The indices are
       * expressed as chars because they are unsigned 16-bit values.
       * @param indicesOffset the index in the indices array where the index data
       *        starts.
       * @param indexCount the number of indices in use. Typically a multiple of
       * three. If not a multiple of three, the remaining one or two indices will
       * be ignored.
       * @return 2 if all of the mesh is visible, 1 if some part of the mesh is
       *         visible, 0 if no part is visible.
       *
       * @throws IllegalArgumentException if ws is null, wsOffset < 0,
       * positions is null, positionsOffset < 0, indices is null,
       * indicesOffset < 0, indicesOffset > indices.length - indexCount
       */
      public static native int visibilityTest(float[] ws, int wsOffset,
              float[] positions, int positionsOffset, char[] indices,
              int indicesOffset, int indexCount);
  
      /**
       * Given an OpenGL ES ModelView-Projection matrix (which implicitly
       * describes a frustum) and a list of spheres, determine which spheres
       * intersect the frustum.
       * <p>
       * A ModelView-Projection matrix can be computed by multiplying the
       * a Projection matrix by the a ModelView matrix (in that order.). There
       * are several possible ways to obtain the current ModelView and
       * Projection matrices. The most generally applicable way is to keep
       * track of the current matrices in application code. If that is not
       * convenient, there are two optional OpenGL ES extensions which may
       * be used to read the current matrices from OpenGL ES:
       * <ul>
       * <li>GL10Ext.glQueryMatrixxOES
       * <li>GL11.GL_MODELVIEW_MATRIX_FLOAT_AS_INT_BITS_OES and
       * GL_PROJECTION_MATRIX_FLOAT_AS_INT_BITS_OES
       * </ul>
       * The problem with reading back the matrices is that your application
       * will only work with devices that support the extension(s) that
       * it uses.
       * <p>
       * A frustum is a six-sided truncated pyramid that defines the portion of
       * world space that is visible in the view.
       * <p>
       * Spheres are described as four floating point values: x, y, z, and r, in
       * world-space coordinates. R is the radius of the sphere.
       * <p>
       * @param mvp a float array containing the mode-view-projection matrix
       * @param mvpOffset The offset of the mvp data within the mvp array.
       * @param spheres a float array containing the sphere data.
       * @param spheresOffset an offset into the sphere array where the sphere
       *        data starts
       * @param spheresCount the number of spheres to cull.
       * @param results an integer array containing the indices of the spheres
       * that are either contained entirely within or intersect the frustum.
       * @param resultsOffset an offset into the results array where the results
       *        start.
       * @param resultsCapacity the number of array elements available for storing
       *        results.
       * @return the number of spheres that intersected the frustum. Can be
       * larger than resultsCapacity, in which case only the first resultsCapacity
       * results are written into the results array.
       *
       * @throws IllegalArgumentException if mvp is null, mvpOffset < 0,
       * mvpOffset > mvp.length - 16, spheres is null, spheresOffset < 0,
       * spheresOffset > spheres.length - sphereCount,
       * results is null, resultsOffset < 0, resultsOffset > results.length -
       * resultsCapacity.
       */
      public static native int frustumCullSpheres(float[] mvp, int mvpOffset,
              float[] spheres, int spheresOffset, int spheresCount,
              int[] results, int resultsOffset, int resultsCapacity);
  
      /**
       * Compute a bounding sphere for a set of points. It is approximately the
       * minimal bounding sphere of an axis-aligned box that bounds the points.
       *
       * @param positions positions in x, y, z triples
       * @param positionsOffset offset into positions array
       * @param positionsCount number of position triples to process
       * @param sphere array containing the output as (x, y, z, r)
       * @param sphereOffset offset where the sphere data will be written
       *
       * @throws IllegalArgumentException if positions is null,
       * positionsOffset < 0, positionsOffset > positions.length - positionsCount,
       * sphere is null, sphereOffset < 0, sphereOffset > sphere.length - 4.
       */
      public static native void computeBoundingSphere(float[] positions,
              int positionsOffset, int positionsCount, float[] sphere,
              int sphereOffset);
  }
  