Visibility
public
class
Visibility
extends Object
A collection of utility methods for computing the visibility of triangle
meshes.
Summary
Public methods |
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static
void
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computeBoundingSphere(float[] positions, int positionsOffset, int positionsCount, float[] sphere, int sphereOffset)
Compute a bounding sphere for a set of points.
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static
int
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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.
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static
int
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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.
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Inherited methods |
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From class
java.lang.Object
Object
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clone()
Creates and returns a copy of this object.
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boolean
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equals(Object obj)
Indicates whether some other object is "equal to" this one.
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void
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finalize()
Called by the garbage collector on an object when garbage collection
determines that there are no more references to the object.
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final
Class<?>
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getClass()
Returns the runtime class of this Object.
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int
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hashCode()
Returns a hash code value for the object.
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final
void
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notify()
Wakes up a single thread that is waiting on this object's
monitor.
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final
void
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notifyAll()
Wakes up all threads that are waiting on this object's monitor.
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String
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toString()
Returns a string representation of the object.
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final
void
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wait(long timeout, int nanos)
Causes the current thread to wait until another thread invokes the
notify() method or the
notifyAll() method for this object, or
some other thread interrupts the current thread, or a certain
amount of real time has elapsed.
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final
void
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wait(long timeout)
Causes the current thread to wait until either another thread invokes the
notify() method or the
notifyAll() method for this object, or a
specified amount of time has elapsed.
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final
void
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wait()
Causes the current thread to wait until another thread invokes the
notify() method or the
notifyAll() method for this object.
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Public constructors
Visibility
public Visibility ()
Public methods
computeBoundingSphere
public static 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
public 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.
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 |
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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 |
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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
public 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. 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 |
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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 |
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IllegalArgumentException |
if ws is null, wsOffset < 0,
positions is null, positionsOffset < 0, indices is null,
indicesOffset < 0, indicesOffset > indices.length - indexCount |
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