asteroidgen/src/Polygoniser.cpp

#include "Polygoniser.h"

#include <functional>
#include <map>

#include <glm/gtc/epsilon.hpp>

#include <MarchingCube.h>

static const int isocells = 32;

Polygonizer::Polygonizer(Density &density, float isolevel) :
		density(density), isolevel(isolevel) {
	updateIsocell();
}

void Polygonizer::setIsoLevel(float isolevel) {
	bool needIsocellUpdate = false;
	if (this->isolevel != isolevel) {
		this->isolevel = isolevel;
		needIsocellUpdate = true;
	}
	needIsocellUpdate |= (isocellVersion != density.getVersion());
	if (needIsocellUpdate)
		updateIsocell();
}

void Polygonizer::updateIsocell() {
	isocell.clear();
	isocell.reserve(isocells * isocells * isocells);

	float step = 1. / isocells;
	for (size_t ix = 0; ix < isocells; ix++) {
		float xmin = ix * step;
		float xmax = xmin + step;
		for (size_t iy = 0; iy < isocells; iy++) {
			float ymin = iy * step;
			float ymax = ymin + step;

			float xyz = density(vec3(xmin, ymin, 0));
			float Xyz = density(vec3(xmax, ymin, 0));
			float xYz = density(vec3(xmin, ymax, 0));
			float XYz = density(vec3(xmax, ymax, 0));
			bool zAllUnder = (xyz < isolevel) && (Xyz < isolevel)
					&& (xYz < isolevel) && (XYz < isolevel);
			bool zAllOver = (xyz > isolevel) && (Xyz > isolevel)
					&& (xYz > isolevel) && (XYz > isolevel);

			for (size_t iz = 0; iz < isocells; iz++) {
				float zmin = iz * step;
				float zmax = zmin + step;

				float xyZ = density(vec3(xmin, ymin, zmax));
				float XyZ = density(vec3(xmax, ymin, zmax));
				float xYZ = density(vec3(xmin, ymax, zmax));
				float XYZ = density(vec3(xmax, ymax, zmax));
				bool ZAllUnder = (xyZ < isolevel) && (XyZ < isolevel)
						&& (xYZ < isolevel) && (XYZ < isolevel);
				bool ZAllOver = (xyZ > isolevel) && (XyZ > isolevel)
						&& (xYZ > isolevel) && (XYZ > isolevel);

				isocell[ix * isocells * isocells + iy * isocells + iz] =
						(zAllUnder && ZAllUnder) || (zAllOver && ZAllOver);

				xyz = xyZ;
				Xyz = XyZ;
				xYz = xYZ;
				XYz = XYZ;
				zAllUnder = ZAllUnder;
				zAllOver = ZAllOver;
			}
		}
	}
	isocellVersion = density.getVersion();
}

void Polygonizer::polygonize(const glm::vec3 lower, const glm::vec3 upper,
		float resolution) {

	size_t nSteps = 1.f / resolution - 1;
	size_t nT = 0;
	for (size_t ix = 0; ix < nSteps; ix++) {
		double x = (double(ix) + 0.5) * resolution;
		for (size_t iy = 0; iy < nSteps; iy++) {
			double y = (double(iy) + 0.5) * resolution;
			for (size_t iz = 0; iz < nSteps; iz++) {
				double z = (double(iz) + 0.5) * resolution;

				GRIDCELL gridCell;
				gridCell.p[0] = vec3(x, y, z);
				gridCell.p[1] = vec3(x + resolution, y, z);
				gridCell.p[2] = vec3(x + resolution, y + resolution, z);
				gridCell.p[3] = vec3(x, y + resolution, z);
				gridCell.p[4] = vec3(x, y, z + resolution);
				gridCell.p[5] = vec3(x + resolution, y, z + resolution);
				gridCell.p[6] = vec3(x + resolution, y + resolution,
						z + resolution);
				gridCell.p[7] = vec3(x, y + resolution, z + resolution);

				for (size_t iCell = 0; iCell < 8; iCell++) {
					gridCell.val[iCell] = density(gridCell.p[iCell]);
				}

				TRIANGLE tris[6];
				int nTris = Polygonise(gridCell, isolevel, tris);
				nT += nTris;
				for (int iTri = 0; iTri < nTris; iTri++) {
					vec3 *ps = tris[iTri].p;

					// skip degenerate vertices
					if (all(epsilonEqual(ps[0], ps[1], 1e-8f))
							|| all(epsilonEqual(ps[0], ps[2], 1e-8f))
							|| all(epsilonEqual(ps[2], ps[1], 1e-8f)))
						continue;

					glm::uvec3 idc;
					for (size_t k = 0; k < 3; k++) {
						glm::vec3 &p = tris[iTri].p[k];
						std::map<glm::vec3, int>::iterator vit =
								vertexLookup.find(p);
						if (vit != vertexLookup.end()) {
							idc[k] = vit->second;
						} else {
							idc[k] = vertices.size();
							vertices.push_back(p);
							vertexLookup[p] = idc[k];
						}
					}
					indices.push_back(idc);
				}
			}
		}
	}
}

void Polygonizer::polygonize(float resolution) {
	vertexLookup.clear();
	vertices.clear();
	indices.clear();

// coarse scan
	float coarseResolution = resolution * 10;

	size_t nSteps = 1.f / resolution - 1;
	size_t nT = 0;
	for (size_t ix = 0; ix < nSteps; ix++) {
		double x = (double(ix) + 0.5) * resolution;
		for (size_t iy = 0; iy < nSteps; iy++) {
			double y = (double(iy) + 0.5) * resolution;
			for (size_t iz = 0; iz < nSteps; iz++) {
				double z = (double(iz) + 0.5) * resolution;

				GRIDCELL gridCell;
				gridCell.p[0] = vec3(x, y, z);
				gridCell.p[1] = vec3(x + resolution, y, z);
				gridCell.p[2] = vec3(x + resolution, y + resolution, z);
				gridCell.p[3] = vec3(x, y + resolution, z);
				gridCell.p[4] = vec3(x, y, z + resolution);
				gridCell.p[5] = vec3(x + resolution, y, z + resolution);
				gridCell.p[6] = vec3(x + resolution, y + resolution,
						z + resolution);
				gridCell.p[7] = vec3(x, y + resolution, z + resolution);

				for (size_t iCell = 0; iCell < 8; iCell++) {
					gridCell.val[iCell] = density(gridCell.p[iCell]);
				}

				TRIANGLE tris[6];
				int nTris = Polygonise(gridCell, isolevel, tris);
				nT += nTris;
				for (int iTri = 0; iTri < nTris; iTri++) {
					vec3 *ps = tris[iTri].p;

					// skip degenerate vertices
					if (all(epsilonEqual(ps[0], ps[1], 1e-8f))
							|| all(epsilonEqual(ps[0], ps[2], 1e-8f))
							|| all(epsilonEqual(ps[2], ps[1], 1e-8f)))
						continue;

					glm::uvec3 idc;
					for (size_t k = 0; k < 3; k++) {
						glm::vec3 &p = tris[iTri].p[k];
						std::map<glm::vec3, int>::iterator vit =
								vertexLookup.find(p);
						if (vit != vertexLookup.end()) {
							idc[k] = vit->second;
						} else {
							idc[k] = vertices.size();
							vertices.push_back(p);
							vertexLookup[p] = idc[k];
						}
					}
					indices.push_back(idc);
				}
			}
		}
	}

}