Drawing a lines radiating from every angle using Bresenham line algorithm

Question

I am trying to recreate a image like this

... or just each point

Using Bresenham line algorithm, but can't seem to able to do so.. The point i receive from my computation doesn't look like a like, and output from the different angles don't make sense for instance.

I start from the center (3,3), and want to draw with a certain angle with a given radius..

angle: 1
13,19
bressenham: 
mark: 3,3
mark: 3,3
mark: 4,4
mark: 4,4
mark: 5,5
mark: 5,5
mark: 6,6
mark: 6,6
mark: 7,7
mark: 7,7
mark: 8,8
mark: 8,8
mark: 9,9
mark: 9,9
mark: 10,10
mark: 10,10
mark: 11,11
mark: 11,11
mark: 12,12
mark: 12,12
1319
angle: 2
-5,21
bressenham: 
mark: -5,3
mark: -5,3
mark: -5,4
mark: -4,5
mark: -4,5
mark: -4,6
mark: -3,7
mark: -3,7
mark: -3,8
mark: -2,9
mark: -2,9
mark: -2,10
mark: -1,11
mark: -1,11
mark: -1,12
mark: 0,13
mark: 0,13
mark: 0,14
mark: 1,15
mark: 1,15
mark: 1,16
mark: 2,17
mark: 2,17
mark: 2,18
-521

For angle 1 => the angle is set to one.. (13,19) is the position of the endpoint located at the given length. and all the mark: are those pixels which are being marked by the algorithm.. That one makes sense, but, when i do the same for angle = 2.. something messes up.. I don't know why, but it would be very helpful if any of you could help me solve this problem.

Here is the code i used to compute these output.

#include <iostream>
#include <math.h>
using namespace std;

int sign(double x ){ return (x > 0) ? 1 : ((x < 0) ? -1 : 0); }

std::pair<int,int> endpoint(double angle, int x1 , int y1, int lenght)
{

    if(angle == 90)
    {
        double y2 = y1+lenght;
        return std::make_pair(x1, -y2);
    }
    if(angle == 180)
    {
        double x2 = x1+lenght;
        return std::make_pair(-x2, y1);
    }
    if(angle == 270)
    {
        double y2 = y1+lenght;
        return std::make_pair(x1, y2);
    }


    double x2 = x1 + (lenght * cos(angle));
    double y2 = y1 + (lenght * sin(angle));
    return std::make_pair(x2,y2);
}


void bresenham(int x0, int y0, int x1, int y1)
{
    int dx = x1-x0;
    int dy = y1 - y0;
    if (abs(dx) > abs(dy))
    {
        // x-axis
        int j = y0;
        double e = dy - dx;

        for (int i = x0; i<x1; i++)
        {
            std::cout << "marked: " << i << ","<< j << std::endl;
            if( e >= 0)
            {
                j += 1;
                e -= dx;
            }
            e += dy;

        }
    }
    else if(abs(dx)<abs(dy))
    {
        // y-axis

        int j = x0;
        double e = dx - dy;

        for (int i = y0; i<y1; i++)
        {
            std::cout << "marked: " << j<< ","<< i << std::endl;
            if( e >= 0)
            {
                j += 1;
                e -= dy;
            }
            e += dx;

        }


    }

}


void line(int x0, int y0, int x1, int y1)
{

    if(x1 < x0)
    {
        swap(x1, x0);
    }

    if(y1 < y0)
    {
        swap(y1, y0);
    }


    int dx = x1-x0;
    int dy = y1-y0;
    double e = 0;
    if(dx == 0)
    {
        if (sign(dy) == -1)
        {
            cout << "new" << endl;
            for (int y = y0; y != y1; y--)
            {
                cout << "mark" << x1 << "," << y << endl;
            }

        }
        else
        {
            for (int y = y0; y != y1; y++)
            {
                cout << "mark" << x1 << "," << y << endl;
            }
        }
        return;
    }

    else if(dy == 0)
    {

        if (sign(dx) == -1)
        {
            cout << "new" << endl;

            for (int x = x0; x != x1; x--)
            {
                cout << "mark" << x << "," << y1 << endl;
            }

        }
        else
        {
            for (int y = y0; y != y1; y++)
            {
                cout << "mark" << x1 << "," << y << endl;
            }
        }
        return;
    }
    cout << "bressenham: " << endl;
    double de = abs(dy/dx);
    int y = y0;
    for (int x = x0; x != x1; x++)
    {
        cout << "mark: " << x << "," << y << endl;
        e = e + de;
        while (e >= 0.5)
        {
            cout << "mark: " << x << "," << y << endl;
            y = y + sign(y1-y0);
            e = e -1;
        }
    }


}

int main(int argc, const char * argv[])
{
    for (int angle = 0; angle < 180; angle++)
    {
        cout << "angle: " << angle << endl;
        pair<int, int> end = endpoint(angle, 3, 3, 20);
        cout << end.first << end.second << endl;
        line(3, 3, end.first, end.second);
        cout << end.first << end.second << endl;

    }
    return 0;
}

Answer 1

This might not be your only issue but I noticed you're using sin and cos with degrees. You must first convert your angles to radians for those functions to work properly (read "Parameters" here):

#define PI 3.14159265

std::pair<int,int> endpoint(double angle, int x1 , int y1, int length)
{ 
    // ...
    double x2 = x1 + (length * cos(angle * PI / 180.0 ));
    double y2 = y1 + (length * sin(angle * PI / 180.0 ));
    return std::make_pair(x2,y2);
}

Also, you spelt "length" wrong ;b