128 lines
4.0 KiB
C++
128 lines
4.0 KiB
C++
#pragma once
|
|
|
|
/** Implement the Marching Cubes algorithm
|
|
*
|
|
* Marching cubes:
|
|
* W. E. Lorensen, H. E. Cline, 1987
|
|
* ``Marching cubes: a high resulution 3D surface construction algorithm''
|
|
* <http://fab.cba.mit.edu/classes/S62.12/docs/Lorensen_marching_cubes.pdf>
|
|
*/
|
|
|
|
#include <vector>
|
|
#include "Mesh.hpp"
|
|
#include "Implicit.hpp"
|
|
#include "common_structures.hpp"
|
|
|
|
class MarchingCubes {
|
|
private:
|
|
class Intersections {
|
|
public:
|
|
typedef unsigned char intersect_t;
|
|
Intersections() : inters(0) {}
|
|
|
|
intersect_t value() const {
|
|
return inters;
|
|
}
|
|
|
|
/** The corners are indexed with three booleans, one for each
|
|
* axis (x, y, z). A false value means a lower coordinate along
|
|
* this axis.
|
|
* Eg., (false, true, false) means the corner (0, 1, 0) for a
|
|
* cube of side 1 placed at (0, 0, 0).
|
|
*/
|
|
|
|
void set_corner(bool x, bool y, bool z, bool val) {
|
|
intersect_t mask = 1 << (shift(x, y, z));
|
|
if(val)
|
|
inters |= mask;
|
|
else
|
|
inters &= ~mask;
|
|
}
|
|
bool get_corner(bool x, bool y, bool z) const {
|
|
return (inters & (1 << shift(x, y, z))) == 1;
|
|
}
|
|
|
|
private:
|
|
intersect_t inters;
|
|
|
|
int shift(bool x, bool y, bool z) const {
|
|
return x + (y << 1) + (z << 2);
|
|
}
|
|
};
|
|
|
|
public:
|
|
MarchingCubes(
|
|
const ImplicitSurface& surface,
|
|
const Cuboid& box=Cuboid(
|
|
Point(-20, -20, -20),
|
|
Point(20, 20, 20)),
|
|
double resolution=.25);
|
|
|
|
/** Add a starting point hint
|
|
*
|
|
* A hint is a cuboid that should intersect at least once the surface,
|
|
* such that the marching cube will find the surface there and will be
|
|
* able to follow it.
|
|
* If at least a hint is given, the algorithm will expect that at least
|
|
* a hint per disjoint surface is given, ie. that it is safe to only
|
|
* follow the surface starting from the hints, and ignoring the parts
|
|
* of the grid that are "far" from the hints.
|
|
*/
|
|
void add_hint(const Cuboid& hint);
|
|
|
|
Mesh operator()();
|
|
|
|
struct CubeEdge {
|
|
CubeEdge() {}
|
|
CubeEdge(bool x0, bool y0, bool z0,
|
|
bool x1, bool y1, bool z1)
|
|
{
|
|
x[0] = x0;
|
|
y[0] = y0;
|
|
z[0] = z0;
|
|
x[1] = x1;
|
|
y[1] = y1;
|
|
z[1] = z1;
|
|
}
|
|
bool x[2], y[2], z[2];
|
|
|
|
bool operator==(const CubeEdge& oth) const {
|
|
return x[0] == oth.x[0] && x[1] == oth.x[1]
|
|
&& y[0] == oth.y[0] && y[1] == oth.y[1]
|
|
&& z[0] == oth.z[0] && z[1] == oth.z[1];
|
|
}
|
|
|
|
/** Get the space point at a given position of [0,1] along the edge
|
|
* when the base of the cube (ie. (0, 0, 0)) is given. */
|
|
Point at(double pos,
|
|
double bx, double by, double bz, double resolution) const;
|
|
};
|
|
struct CubeTri {
|
|
CubeTri() {}
|
|
CubeTri(const CubeEdge* edge_) {
|
|
for(size_t i=0; i < 3; ++i)
|
|
edge[i] = edge_[i];
|
|
}
|
|
CubeTri(const CubeEdge e0, const CubeEdge e1, const CubeEdge e2) {
|
|
edge[0] = e0;
|
|
edge[1] = e1;
|
|
edge[2] = e2;
|
|
}
|
|
CubeEdge edge[3];
|
|
};
|
|
|
|
private: //methods
|
|
Point intersect_location(const CubeEdge& edge,
|
|
double bx, double by, double bz) const;
|
|
|
|
private:
|
|
|
|
static const std::vector<CubeTri> edges_of_intersection[256];
|
|
|
|
const ImplicitSurface& surface;
|
|
Cuboid box;
|
|
double resolution;
|
|
|
|
std::vector<Cuboid> hints;
|
|
};
|