frink.graphics

Class MarchingCubes

java.lang.Object

frink.graphics.MarchingCubes

public class MarchingCubes
extends java.lang.Object

This class contains routines for finding a polygon surface mesh or "isosurface" for a scalar field. It can also find a surface mesh for a VoxelArray. It is adapted from the public-domain C / OpenGL Marching Cubes Example Program by Cory Bloyd (corysama@yahoo.com) found at http://paulbourke.net/geometry/polygonise/marchingsource.cpp For a description of the algorithm go to http://paulbourke.net/geometry/polygonise/

Author:

Alan Eliasen, eliasen@mindspring.com

Field Summary

Fields

Modifier and Type	Field and Description
private static int[]	cubeEdgeFlags For any edge, if one vertex is inside of the surface and the other is outside of the surface then the edge intersects the surface.
private static int[][]	edgeConnection edgeConnection lists the index of the endpoint vertices for each of the 12 edges of the cube.
private static float[][]	edgeDirection edgeDirection lists the direction vector (vertex1-vertex0) for each edge in the cube.
private static int[][]	triangleConnection For each of the possible vertex states listed in cubeEdgeFlags there is a specific triangulation of the edge intersection points.
private static float[][]	vertexOffset vertexOffset lists the positions, relative to vertex0, of each of the 8 vertices of a cube.

Constructor Summary

Constructors

Constructor and Description
MarchingCubes()

Method Summary

Modifier and Type	Method and Description
private static float	fGetOffset(float fValue1, float fValue2, float fValueDesired) fGetOffset finds the approximate point of intersection of the surface between two points with the values fValue1 and fValue2.
(package private) Point3DFloat	getColor(Point3DFloat rfPosition, Point3DFloat rfNormal) getColor generates a color from a given position and normal of a point.
static java.util.Vector<Triangle3DFloat>	triangulateHull(float xMin, float xMax, int xSteps, float yMin, float yMax, int ySteps, float zMin, float zMax, int zSteps, Field3DFloat field, float targetValue) triangulateHull iterates over a Field3DFloat and returns a vector of triangles that represent its external hull, with the external hull being defined as the points that are greater than or equal to targetValue.

Methods inherited from class java.lang.Object

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

Field Detail

vertexOffset

private static final float[][] vertexOffset

vertexOffset lists the positions, relative to vertex0, of each of the 8 vertices of a cube.

edgeConnection

private static final int[][] edgeConnection

edgeConnection lists the index of the endpoint vertices for each of the 12 edges of the cube.

edgeDirection

private static final float[][] edgeDirection

edgeDirection lists the direction vector (vertex1-vertex0) for each edge in the cube.

cubeEdgeFlags

private static final int[] cubeEdgeFlags

For any edge, if one vertex is inside of the surface and the other is outside of the surface then the edge intersects the surface. For each of the 8 vertices of the cube can be two possible states : either inside or outside of the surface. For any cube the are 2^8=256 possible sets of vertex states. This table lists the edges intersected by the surface for all 256 possible vertex states. There are 12 edges. For each entry in the table, if edge #n is intersected, then bit #n is set to 1.

triangleConnection

private static final int[][] triangleConnection

For each of the possible vertex states listed in cubeEdgeFlags there is a specific triangulation of the edge intersection points. triangleConnection lists all of them in the form of 0-5 edge triples with the list terminated by the invalid value -1. For example: triangleConnection[3] lists the 2 triangles formed when corner[0] and corner[1] are inside of the surface, but the rest of the cube is not. I found this table in an example program someone wrote long ago. It was probably generated by hand.

Constructor Detail

MarchingCubes

public MarchingCubes()

Method Detail

fGetOffset

private static float fGetOffset(float fValue1,
                                float fValue2,
                                float fValueDesired)

fGetOffset finds the approximate point of intersection of the surface between two points with the values fValue1 and fValue2.

getColor

Point3DFloat getColor(Point3DFloat rfPosition,
                      Point3DFloat rfNormal)

getColor generates a color from a given position and normal of a point.

triangulateHull

public static java.util.Vector<Triangle3DFloat> triangulateHull(float xMin,
                                                                float xMax,
                                                                int xSteps,
                                                                float yMin,
                                                                float yMax,
                                                                int ySteps,
                                                                float zMin,
                                                                float zMax,
                                                                int zSteps,
                                                                Field3DFloat field,
                                                                float targetValue)

triangulateHull iterates over a Field3DFloat and returns a vector of triangles that represent its external hull, with the external hull being defined as the points that are greater than or equal to targetValue.