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java.lang.Object de.grogra.vecmath.geom.VolumeBase de.grogra.vecmath.geom.MeshVolume
public class MeshVolume
This class represents a given Mesh
as a Volume
. It uses an octree
in order to speed up the intersection computation; an octree
cell contains a list of those polygons of the mesh which lie within
the cell.
The algorithm for a single polygonline intersection is an extension to general polygonal meshes (with convex, planar polygons) of the algorithm in the paper "Ray Tracing Triangular Meshes" of John Amanatides and Kin Choi. The algorithm uses Plücker coordinates to decide if a line intersects a polygon.
The mesh coordinates are specified in their own coordinate system.
The transformation from world coordinates to mesh coordinates is
implemented by worldToMesh
. The advantage of this is that
it is possible to create a set of copies of a MeshVolume
using dup()
which can then be shifted to another location
using setTransformation(Matrix4d)
.
To set the data of a MeshVolume
, both methods
setMesh(de.grogra.vecmath.geom.Mesh)
and setTransformation(javax.vecmath.Matrix4d)
have to be invoked
in this order.
Field Summary  

static int 
MIN_CELL_OBJECTS
Minimum number of polygons which have to be present in an octree cell so that it is considered for subdivision. 
Constructor Summary  

MeshVolume()

Method Summary  

boolean 
boxContainsBoundary(BoundingBox box,
Tuple3d center,
double radius,
Variables temp)
Returns true if the specified box contains
(part of) the boundary surface of this volume. 
void 
computeFaceNormal(Intersection is,
Vector3d normal)
Compute the face normal of the triangle that was hit (is.face). 
boolean 
computeIntersections(Line line,
int which,
IntersectionList list,
Intersection excludeStart,
Intersection excludeEnd)
Computes intersections between the boundary surface of this object and the specified line . 
void 
computeNormal(Intersection is,
Vector3d normal)
This method computes the unit normal vector of an intersection is which has been computed previously by the invocation
of Volume.computeIntersections(de.grogra.vecmath.geom.Line, int, de.grogra.vecmath.geom.IntersectionList, de.grogra.vecmath.geom.Intersection, de.grogra.vecmath.geom.Intersection) on this volume. 
void 
computeTangents(Intersection is,
Vector3d dpdu,
Vector3d dpdv)
This method computes the derivatives of the surface point (as function of the uvcoordinates, see Volume.computeUV(de.grogra.vecmath.geom.Intersection, javax.vecmath.Vector2d) )
with respect to u and v at the intersection point. 
void 
computeUV(Intersection is,
Vector2d uv)
This method computes the uvcoordinates of an intersection point is which has been computed previously by the invocation
of Volume.computeIntersections(de.grogra.vecmath.geom.Line, int, de.grogra.vecmath.geom.IntersectionList, de.grogra.vecmath.geom.Intersection, de.grogra.vecmath.geom.Intersection) on this volume. 
boolean 
contains(Tuple3d point,
boolean open)
Determines if the given point lies within this object. 
MeshVolume 
dup()
Creates a duplicate of this mesh. 
void 
getExtent(Tuple3d min,
Tuple3d max,
Variables temp)
Computes the extent of this volume, i.e., an axisaligned bounding box between min and max . 
Octree 
getOctree()

int 
getPolygonCount()

void 
setMesh(Mesh mesh)
Sets the mesh of this volume to the specified mesh . 
void 
setTransformation(Matrix4d meshToWorld)
Sets the transformation from mesh coordinates to global world coordinates. 
Methods inherited from class de.grogra.vecmath.geom.VolumeBase 

addConvexIntersections, getId, operator$and, operator$com, operator$or, operator$sub, setId 
Methods inherited from class java.lang.Object 

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait 
Field Detail 

public static int MIN_CELL_OBJECTS
Constructor Detail 

public MeshVolume()
Method Detail 

public boolean boxContainsBoundary(BoundingBox box, Tuple3d center, double radius, Variables temp)
Volume
true
if the specified box
contains
(part of) the boundary surface of this volume. Otherwise, if box and
boundary do not overlap, this method should return false
,
but may also return true
if an exact computation
would be too expensive or complicated.
Note that a box contains the boundary of a closed set S iff both have a nonempty intersection and the box is not contained in the open set of S.
boxContainsBoundary
in interface Volume
box
 bounding boxcenter
 center coordinates of boxradius
 radius of enclosing spheretemp
 has to be provided by the invoker, may be used in implementations
true
if box contains (part of) the boundary of this volumepublic void computeFaceNormal(Intersection is, Vector3d normal)
is
 intersection between this volume and a raynormal
 output memory for computed normal vectorpublic boolean computeIntersections(Line line, int which, IntersectionList list, Intersection excludeStart, Intersection excludeEnd)
Volume
line
. The intersections are added
to list
in ascending order of distance
(i.e., of Intersection.parameter
), where the
parameter
has to lie between line.start
and line.end
.
Implementations of this method must not
clear or modify the existing intersections in list
.
The parameter which
has to be one of
Intersection.ALL
, Intersection.CLOSEST
,
Intersection.ANY
. It determines if all intersections
have to be added to the list, only the closest (minimal
value of Intersection.parameter
), or an arbitrary
of the set of all intersections. Only in case of ALL
,
the return value of this method is precise.
If specific intersection points should be excluded from the list
of computed intersections, they have to be specified in
excludeStart
and excludeEnd
.
The intersection point of excludeStart
has to be the
starting point of line
, the intersection point of
excludeEnd
has to be the end point of line
.
The exclusion of intersections is a useful feature for
raytracing, e.g., when a ray is reemitted at an intersection point
in another direction.
computeIntersections
in interface Volume
line
 a linewhich
 one of Intersection.ALL
,
Intersection.CLOSEST
, Intersection.ANY
, this
determines which intersections have to be added to list
list
 the intersections are added to this listexcludeStart
 intersection at start point which shall be excluded, or null
excludeEnd
 intersection at end point which shall be excluded, or null
true
iff the beginning of the line lies
within the volume (i.e., if the line starts within the volume or
enters the volume at the starting point); however note that the returned
value is valid only if which == Intersection.ALL
public void computeNormal(Intersection is, Vector3d normal)
Volume
is
which has been computed previously by the invocation
of Volume.computeIntersections(de.grogra.vecmath.geom.Line, int, de.grogra.vecmath.geom.IntersectionList, de.grogra.vecmath.geom.Intersection, de.grogra.vecmath.geom.Intersection)
on this volume.
computeNormal
in interface Volume
is
 a previously computed intersectionnormal
 resulting unit vector is placed in herepublic void computeTangents(Intersection is, Vector3d dpdu, Vector3d dpdv)
Volume
Volume.computeUV(de.grogra.vecmath.geom.Intersection, javax.vecmath.Vector2d)
)
with respect to u and v at the intersection point.
computeTangents
in interface Volume
is
 a previously computed intersectiondpdu
 resulting derivative with respect to udpdv
 resulting derivative with respect to vpublic void computeUV(Intersection is, Vector2d uv)
Volume
is
which has been computed previously by the invocation
of Volume.computeIntersections(de.grogra.vecmath.geom.Line, int, de.grogra.vecmath.geom.IntersectionList, de.grogra.vecmath.geom.Intersection, de.grogra.vecmath.geom.Intersection)
on this volume.
computeUV
in interface Volume
is
 a previously computed intersectionuv
 resulting uvcoordinates are placed in herepublic boolean contains(Tuple3d point, boolean open)
Volume
point
lies within this object.
If open
is true
, the interior of the volume
is considered (the largest open set contained in the volume,
i.e., excluding the boundary), otherwise the closure of the volume.
contains
in interface Volume
point
 a point in global world coordinatesopen
 consider open or closed set
true
iff point
is an element of the setpublic MeshVolume dup()
setTransformation(Matrix4d)
.
public void getExtent(Tuple3d min, Tuple3d max, Variables temp)
Volume
min
and max
.
getExtent
in interface Volume
min
 minimum coordinates of bounding box are placed in heremax
 maximum coordinates of bounding box are placed in heretemp
 has to be provided by the invoker, may be used in implementationspublic Octree getOctree()
public int getPolygonCount()
public void setMesh(Mesh mesh)
mesh
.
All data is copied, no persistent reference
to mesh
is made. The method
setTransformation(javax.vecmath.Matrix4d)
has to be invoked afterwards to specify
the global coordinate transformation.
mesh
 a meshpublic void setTransformation(Matrix4d meshToWorld)
meshToWorld
 transformation matrix


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