Connecting Polar Graph Coordinates

0
votes

My program is a Polar graphing window. My issue is that when I graph r=a*sin(b*theta). My specific example shown below uses a=12 and b=8. When I connect the point drawn to the next I get something show below:

Polar Graph

The lines seem to be drawn across the petals, which looks wonderful, but is not correct. Below is the code drawing the points and lines:

for(int i=0; i< ptr.size(); i++){
        drawPoint(g2d, ptr.get(i), ptt.get(i));
        if(connectPoints && i!=ptr.size()-1){
            g.drawLine((int)(origin_x+Math.cos(ptt.get(i))*ptr.get(i)*ppp), 
                    (int)(origin_y-Math.sin(ptt.get(i))*ptr.get(i)*ppp), 
                    (int)(origin_x+Math.cos(ptt.get(i+1))*ptr.get(i+1)*ppp), 
                    (int)(origin_y-Math.sin(ptt.get(i+1))*ptr.get(i+1)*ppp));
        }
}

ptr contains the r values and ptt contains the theta values. Here is the line adding the points:

for(double i=0; i<100; i+=0.1){
        pg.plot(12*Math.cos(8*i), i);
}

Why is this happening? How can it be fixed? Thanks ahead of time!

1
javapolar-coordinates

1 Answers

1
votes

You're traversing the circle more than once and your sample points are not the same on each pass. That is why you are getting lines cutting across the petals. Try: 

double numberOfSteps = 1000;
double stepSize = 2.0 * Math.PI / numberOfSteps; 
for(double i=0; i<numberOfSteps; i++){
    double theta = i * stepsize;
    pg.plot(12*Math.cos(8.0 * theta), theta);
}

Experiment with numberOfSteps to fine tune.