Outputs a pixelated circle to the console. Useful for graphics or Minecraft.

voxel_circle.cpp

#include <iostream>
#include <vector>
#include <array>

typedef std::array<float, 2> xyCoord;

float isInCircle(float x, float y, float radius);
void setSquareCoords(int row, int column, std::array<xyCoord, 4>& square);

int main()
{
	enum {x, y};

	float radius;
	int dia;

	std::vector<std::vector<bool>> squares;
	std::array<xyCoord, 4> squareCorners; // coords for square's corners
	squareCorners.fill({{0.0f, 0.0f}});

	// Input diameter
	std::cout << "Diameter: ";
	std::cin >> dia;
	std::cin.ignore();
	std::cout << std::endl;

	squares.resize(dia);

	radius = static_cast<float>(dia) / 2.0f;

	// Generate circle by looping through each row / col position
	for (int row = 0; row < dia; row++)
	{
		for (int col = 0; col < dia; col++)
		{
			int sum = 0;
			setSquareCoords(row, col, squareCorners);
			// If 2/4 corners of block are inside circle radius, block is inside circles
			for (auto corner : squareCorners)
			{
				if (isInCircle(corner[x], corner[y], radius))
					sum++;
			}
			if (sum >= 2)
				squares[row].push_back(true);
			else
				squares[row].push_back(false);
		}
	}

	// output to console
	for (auto row : squares)
	{
		for (auto position : row)
		{
			if (position == true)
				std::cout << '#';
			else
				std::cout << ' ';
		}
		std::cout << std::endl;
	}

	std::cin.ignore();
	return 0;
}

float isInCircle(float x, float y, float radius)
{
	x -= radius;
	y -= radius;
	return (x * x + y * y <= radius * radius);
}

void setSquareCoords(int row, int column, std::array<xyCoord, 4>& square)
{
	enum {top_left, top_right, bottom_left, bottom_right};
	enum {x, y};
	for (unsigned corner = 0; corner < square.size(); corner++)
	{
		switch (corner)
		{
			case top_left:
				square[corner][x] = static_cast<float>(row);
				square[corner][y] = static_cast<float>(column);
				break;
			case top_right:
				square[corner][x] = static_cast<float>(row);
				square[corner][y] = static_cast<float>(column) + 1.0f;
				break;
			case bottom_left:
				square[corner][x] = static_cast<float>(row) + 1.0f;
				square[corner][y] = static_cast<float>(column);
				break;
			case bottom_right:
				square[corner][x] = static_cast<float>(row) + 1.0f;
				square[corner][y] = static_cast<float>(column) + 1.0f;
				break;
		}
	}
}