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/*
* 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);
}
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