Creates an animated Koch Snowflake in VPaint's .vec format

CreateKochSnowflake.cpp

#include <iostream>
#include <fstream>
#include <sstream>
#include <vector>
#include <array>
#include <utility>
#include <map>
#include <cmath>

using namespace std;

#define OUTPUT_PATH "VPaintProjects/Result.vec"
// Radius and padding are not guaranteed to be accurate
#define RADIUS 400
#define PADDING 200
// Ignored for this version of the code
// If you want a uniform line width, replace all occurrences of 5*step+5 to LINE_WIDTH and use this macro
#define LINE_WIDTH 200
#define LINE_COLOR "rgba(255,255,255,0.3)"
// A triangle has a subdivision of 0
#define SUBDIVISIONS 4
#define FPS 30
#define DURATION 1

const float offset = RADIUS + PADDING;
const float canvasLength = 2 * offset;

int main() {
	if(SUBDIVISIONS < 1) {
		cerr << "Not enough subdivisions" << endl;
		return -1;
	}

	ofstream output(OUTPUT_PATH);
	// vertexOutput is a workaround for a current VPaint bug where the edges need to be before the vertices
	stringstream vertexOutput;
	output << "<?xml version=\"1.0\" encoding=\"UTF-8\"?><vec version=\"1.6\"><playback framerange=\"0 " << (FPS * DURATION * SUBDIVISIONS) << "\" fps=\"" << FPS << "\" subframeinbetweening=\"off\" playmode=\"normal\"/><canvas position=\"0 0\" size=\"" << canvasLength << " " << canvasLength << "\"/><layer><background color=\"rgba(135,206,250,1)\" image=\"\" position=\"0 0\" size=\"cover\" repeat=\"norepeat\" opacity=\"1\" hold=\"yes\"/><objects>";
	map<int,pair<float,float> > fixedPoints;
	fixedPoints[0] = {offset + RADIUS * cos(M_PI / 2), offset + RADIUS * sin(M_PI / 2)};
	fixedPoints[1 * std::pow(4, SUBDIVISIONS)] = {offset + RADIUS * cos(7 * M_PI / 6), offset + RADIUS * sin(7 * M_PI / 6)};
	fixedPoints[2 * std::pow(4, SUBDIVISIONS)] = {offset + RADIUS * cos(11 * M_PI / 6), offset + RADIUS * sin(11 * M_PI / 6)};
	const int totalPoints = 3 * pow(4, SUBDIVISIONS);
	array<pair<float,float>, totalPoints> pointPositions;
	int edgeStart = (SUBDIVISIONS + 1) * totalPoints;

	int step;
	for(int i = 0; i <= SUBDIVISIONS; i++) {
		// Update inbetween vertices' position if necessary
		for(int j = 0; j < totalPoints; j++) {
			int lowerFixed = j;
			while(!fixedPoints.count(lowerFixed)) --lowerFixed;
			int upperFixed = j;
			while(!fixedPoints.count(upperFixed)) upperFixed = (upperFixed + 1) % totalPoints;
			step = ((upperFixed == 0 ? totalPoints : upperFixed) - lowerFixed) / 4.0;

			// Determine where the point should be at for this iteration
			float calcX, calcY;
			if(j == lowerFixed || j == upperFixed) {
				calcX = fixedPoints[j].first;
				calcY = fixedPoints[j].second;
			}
			else if(lowerFixed+step == j && upperFixed != (j+step) % totalPoints) {
				calcX = fixedPoints[lowerFixed].first + (fixedPoints[upperFixed].first - fixedPoints[lowerFixed].first) / 3;
				calcY = fixedPoints[lowerFixed].second + (fixedPoints[upperFixed].second - fixedPoints[lowerFixed].second) / 3;
			}
			else if(lowerFixed+step != j && upperFixed == (j+step) % totalPoints) {
				calcX = fixedPoints[lowerFixed].first + 2 * (fixedPoints[upperFixed].first - fixedPoints[lowerFixed].first) / 3;
				calcY = fixedPoints[lowerFixed].second + 2 * (fixedPoints[upperFixed].second - fixedPoints[lowerFixed].second) / 3;
			}
			else {
				calcX = 0.5 * (fixedPoints[upperFixed].first + fixedPoints[lowerFixed].first);
				calcY = 0.5 * (fixedPoints[upperFixed].second + fixedPoints[lowerFixed].second);
			}

			vertexOutput << "<vertex id=\"" << ((i * totalPoints) + j) << "\" frame=\"" << (i * FPS * DURATION) << "\" position=\"" << calcX << " " << calcY << "\"/>";
			pointPositions[j].first = calcX;
			pointPositions[j].second = calcY;
			if(j > 0) {
				output << "<edge id=\"" << (edgeStart + i * totalPoints + j) << "\" frame=\"" << (i * FPS * DURATION) << "\" startvertex=\"" << ((i * totalPoints) + j - 1) << "\" endvertex=\"" << ((i * totalPoints) + j) << "\" curve=\"xywdense(5 " << pointPositions[j-1].first << "," << pointPositions[j-1].second << "," << 5*step+5 << " " << calcX << "," << calcY << "," << 5*step+5 << ")\" color=\"" << LINE_COLOR << "\"/>";
			}
		}
		// Close the shape
		output << "<edge id=\"" << (edgeStart + i * totalPoints) << "\" frame=\"" << (i * FPS * DURATION) << "\" startvertex=\"" << ((i + 1) * totalPoints - 1) << "\" endvertex=\"" << (i * totalPoints) << "\" curve=\"xywdense(5 " << pointPositions[totalPoints - 1].first << "," << pointPositions[totalPoints - 1].second << "," << 5*step+5 << " " << pointPositions[0].first << "," << pointPositions[0].second << "," << 5*step+5 << ")\" color=\"" << LINE_COLOR << "\"/>";

		// We don't need to worry about the next part if this is the last iteration
		if(i == SUBDIVISIONS) break;

		// Fix this iterations verticies
		const map<int,pair<float,float> > prevFixedPoints(fixedPoints);
		for(auto iter = prevFixedPoints.begin(); iter != prevFixedPoints.end(); iter++) {
			// Getting the closest fixed points in either direction
			pair<const int, pair<float, float> > begin = *iter;
			auto endIter = next(iter);
			if(endIter == prevFixedPoints.end()) endIter = prevFixedPoints.begin();
			auto end = *endIter;
			// The step is the number of points between each fixed point after this iteration
			int step = ((end.first == 0 ? totalPoints : end.first) - begin.first) / 4.0;

			float jumpLength = sqrt(pow(begin.second.first - end.second.first, 2) + pow(begin.second.second - end.second.second, 2)) / 3;
			float angle = atan2(end.second.second - begin.second.second, end.second.first - begin.second.first) - M_PI / 2;

			// Fix new points, the three points of a newly formed equilateral triangle
			fixedPoints[begin.first+step] = pointPositions[begin.first+step];
			fixedPoints[begin.first+2*step] = {pointPositions[begin.first+2*step].first + cos(angle) * jumpLength, pointPositions[begin.first+2*step].second + sin(angle) * jumpLength};
			fixedPoints[begin.first+3*step] = pointPositions[begin.first+3*step];
		}
	}
	output << vertexOutput.str();

	// Add inbetween vertices/edges
	int inbetweenVStart = 2 * edgeStart;
	int inbetweenEStart = inbetweenVStart + (edgeStart - totalPoints);
	for(int i = 0; i < SUBDIVISIONS; i++) {
		for(int j = 0; j < totalPoints; j++) {
			output << "<inbetweenvertex id=\"" << (inbetweenVStart + i * totalPoints + j) << "\" beforevertex=\"" << (i * totalPoints + j) << "\" aftervertex=\"" << ((i + 1) * totalPoints + j) << "\" color=\"rgba(0,0,0,1)\"/>";
			output << "<inbetweenedge id=\"" << (inbetweenEStart + i * totalPoints + j) << "\" beforepath=\"[" << (edgeStart + i * totalPoints + j) << "+]\" afterpath=\"[" << (edgeStart + (i + 1) * totalPoints + j) << "+]\" startanimatedvertex=\"[" << (inbetweenVStart + i * totalPoints + j) << "]\" endanimatedvertex=\"[" << (inbetweenVStart + i * totalPoints + (j + 1) % totalPoints) << "]\" color=\"" << LINE_COLOR << "\"/>";
		}
	}
	output << "</objects></layer></vec>" << endl;
	output.close();
	return 0;
}