Skip to content

Most visited

Recently visited

navigation

Visibility

public class Visibility
extends Object

java.lang.Object
   ↳ android.opengl.Visibility


A collection of utility methods for computing the visibility of triangle meshes.

Summary

Public constructors

Visibility()

Public methods

static void computeBoundingSphere(float[] positions, int positionsOffset, int positionsCount, float[] sphere, int sphereOffset)

Compute a bounding sphere for a set of points.

static int frustumCullSpheres(float[] mvp, int mvpOffset, float[] spheres, int spheresOffset, int spheresCount, int[] results, int resultsOffset, int resultsCapacity)

Given an OpenGL ES ModelView-Projection matrix (which implicitly describes a frustum) and a list of spheres, determine which spheres intersect the frustum.

static int visibilityTest(float[] ws, int wsOffset, float[] positions, int positionsOffset, char[] indices, int indicesOffset, int indexCount)

Test whether a given triangle mesh is visible on the screen.

Inherited methods

From class java.lang.Object

Public constructors

Visibility

Added in API level 3
Visibility ()

Public methods

computeBoundingSphere

Added in API level 3
void computeBoundingSphere (float[] positions, 
                int positionsOffset, 
                int positionsCount, 
                float[] sphere, 
                int sphereOffset)

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.

Parameters
positions float: positions in x, y, z triples
positionsOffset int: offset into positions array
positionsCount int: number of position triples to process
sphere float: array containing the output as (x, y, z, r)
sphereOffset int: 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.

frustumCullSpheres

Added in API level 3
int frustumCullSpheres (float[] mvp, 
                int mvpOffset, 
                float[] spheres, 
                int spheresOffset, 
                int spheresCount, 
                int[] results, 
                int resultsOffset, 
                int resultsCapacity)

Given an OpenGL ES ModelView-Projection matrix (which implicitly describes a frustum) and a list of spheres, determine which spheres intersect the frustum.

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:

  • GL10Ext.glQueryMatrixxOES
  • GL11.GL_MODELVIEW_MATRIX_FLOAT_AS_INT_BITS_OES and GL_PROJECTION_MATRIX_FLOAT_AS_INT_BITS_OES
The problem with reading back the matrices is that your application will only work with devices that support the extension(s) that it uses.

A frustum is a six-sided truncated pyramid that defines the portion of world space that is visible in the view.

Spheres are described as four floating point values: x, y, z, and r, in world-space coordinates. R is the radius of the sphere.

Parameters
mvp float: a float array containing the mode-view-projection matrix
mvpOffset int: The offset of the mvp data within the mvp array.
spheres float: a float array containing the sphere data.
spheresOffset int: an offset into the sphere array where the sphere data starts
spheresCount int: the number of spheres to cull.
results int: an integer array containing the indices of the spheres that are either contained entirely within or intersect the frustum.
resultsOffset int: an offset into the results array where the results start.
resultsCapacity int: the number of array elements available for storing results.
Returns
int 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.

visibilityTest

Added in API level 3
int visibilityTest (float[] ws, 
                int wsOffset, 
                float[] positions, 
                int positionsOffset, 
                char[] indices, 
                int indicesOffset, 
                int indexCount)

Test whether a given triangle mesh is visible on the screen. The mesh is specified as an indexed triangle list.

Parameters
ws float: the world space to screen space transform matrix, as an OpenGL column matrix.
wsOffset int: an index into the ws array where the data starts.
positions float: the vertex positions (x, y, z).
positionsOffset int: the index in the positions array where the data starts.
indices char: the indices of the triangle list. The indices are expressed as chars because they are unsigned 16-bit values.
indicesOffset int: the index in the indices array where the index data starts.
indexCount int: 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.
Returns
int 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
This site uses cookies to store your preferences for site-specific language and display options.

Hooray!

This class requires API level or higher

This doc is hidden because your selected API level for the documentation is . You can change the documentation API level with the selector above the left navigation.

For more information about specifying the API level your app requires, read Supporting Different Platform Versions.

Take a one-minute survey?
Help us improve Android tools and documentation.