126 lines
4.1 KiB
C++
126 lines
4.1 KiB
C++
#include "MarchingCubes.hpp"
|
|
|
|
#include <cassert>
|
|
|
|
const std::vector<MarchingCubes::CubeTri>
|
|
MarchingCubes::edges_of_intersection[256] = {
|
|
};
|
|
|
|
MarchingCubes::MarchingCubes(
|
|
const ImplicitSurface& surface,
|
|
const Cuboid& box,
|
|
double resolution):
|
|
surface(surface),
|
|
box(box),
|
|
resolution(resolution)
|
|
{}
|
|
|
|
void MarchingCubes::add_hint(const Cuboid& hint) {
|
|
hints.push_back(hint);
|
|
}
|
|
|
|
Mesh MarchingCubes::operator()() {
|
|
Mesh output;
|
|
|
|
for(double x = box.low(0); x < box.high(0) + resolution; x += resolution)
|
|
{
|
|
for(double y = box.low(1); y < box.high(1) + resolution;
|
|
y += resolution)
|
|
{
|
|
for(double z = box.low(2); z < box.high(2) + resolution;
|
|
z += resolution)
|
|
{
|
|
Intersections intersections;
|
|
/* =====
|
|
* NOTE: this code currently computes 8 times the surface value
|
|
* at each corner point of the inspected space. This is okay
|
|
* for now, because such computations are ultra light and
|
|
* actually better than storing values.
|
|
* If a time comes when this computation is heavier, because we
|
|
* are looking at more complex implicit surfaces,
|
|
* IT WILL BE NECESSARY TO ENHANCE THIS CODE!
|
|
* ==== */
|
|
for(int dx=0; dx <= 1; dx++) {
|
|
for(int dy=0; dy <= 1; dy++) {
|
|
for(int dz=0; dz <= 1; dz++) {
|
|
double cx = x + resolution * dx;
|
|
double cy = y + resolution * dy;
|
|
double cz = z + resolution * dz;
|
|
intersections.set_corner(cx, cy, cz,
|
|
surface(cx, cy, cz) > 0);
|
|
}
|
|
}
|
|
}
|
|
|
|
const std::vector<CubeTri>& cur_triangles =
|
|
edges_of_intersection[intersections.value()];
|
|
for(const CubeTri& cube_tri: cur_triangles) {
|
|
Point verts[3] = {
|
|
intersect_location(cube_tri.edge[0],
|
|
x, y, z),
|
|
intersect_location(cube_tri.edge[1],
|
|
x, y, z),
|
|
intersect_location(cube_tri.edge[2],
|
|
x, y, z),
|
|
};
|
|
|
|
size_t vert_ids[3];
|
|
for(int i=0; i < 3; ++i)
|
|
vert_ids[i] = output.add_vertice(verts[i]);
|
|
|
|
for(int i=0; i < 3; ++i) {
|
|
output.add_face(
|
|
vert_ids[i],
|
|
vert_ids[(i+1) % 3],
|
|
vert_ids[(i+2) % 3]);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
return output;
|
|
}
|
|
|
|
Point MarchingCubes::CubeEdge::at(double pos,
|
|
double bx, double by, double bz, double resolution) const
|
|
{
|
|
Point p1(
|
|
bx + x[0] * resolution,
|
|
by + y[0] * resolution,
|
|
bz + z[0] * resolution);
|
|
Point p2(
|
|
bx + x[1] * resolution,
|
|
by + y[1] * resolution,
|
|
bz + z[1] * resolution);
|
|
|
|
return Point(
|
|
pos * (p1.x + p2.x),
|
|
pos * (p1.y + p2.y),
|
|
pos * (p1.z + p2.z));
|
|
}
|
|
|
|
Point MarchingCubes::intersect_location(const CubeEdge& edge,
|
|
double bx, double by, double bz) const
|
|
{
|
|
Point p1 = edge.at(0, bx, by, bz, resolution);
|
|
Point p2 = edge.at(1, bx, by, bz, resolution);
|
|
|
|
std::function<Point(double, double)> compute =
|
|
[&](double low_prop, double high_prop)
|
|
{
|
|
double med_prop = (low_prop + high_prop) / 2;
|
|
Point med = edge.at(med_prop, bx, by, bz, resolution);
|
|
|
|
if(high_prop - low_prop < 1e-8)
|
|
return med;
|
|
|
|
assert(surface(p1) * surface(p2) <= 0); // Can still binary search
|
|
|
|
if(surface(p1) * surface(med) <= 0)
|
|
return compute(low_prop, med_prop);
|
|
return compute(med_prop, high_prop);
|
|
};
|
|
|
|
return compute(0, 1);
|
|
}
|