CODEWITHSUNDEEP
javamathlineangleradians
A. Ferguson
A. Ferguson

Reputation: 29

Java: How would I draw a line at an angle other than 45 degrees or zero degrees etc.?

I've been researching fractals and decided to give it a try, but immediately ran into a much simpler issue. I can't draw a line at any angle other than 0, 45, 90, ... etc.

The problem: My angle is an integer, and I'm using Math.toRadians(angle) to calculate the angle itself as its drawn. When I draw the line, I have to cast (int) to the double produced from Math.toRadians(), which causes me to lose the angle itself and I believe is what prevents the line from being drawn.

The code I'm using: `

    Graphics2D g2d = (Graphics2D) g;

    int angle = 90; 

    int startX = getWidth()/2;
    int startY = getHeight()/2;
    int length = 100;

    int endX = startX + (int)Math.cos(Math.toRadians(angle)) * length;
    int endY = startY + (int)Math.sin(Math.toRadians(angle)) * length;

    g2d.drawLine(startX, startY, endX, endY);

`

Solution:

    Graphics2D g2d = (Graphics2D) g;

    int angle = 91; 

    int startX = getWidth()/2;
    int startY = getHeight()/2;
    int length = 100;



    int endX = startX + (int)(Math.cos(Math.toRadians(angle)) * length);
    int endY = startY + (int)(Math.sin(Math.toRadians(angle)) * length);

    g2d.drawLine(startX, startY, endX, endY);

Thanks guys!

Upvotes: 1

Views: 1924

Answers (2)

laune
laune

Reputation: 31290

For best precision, use Math.round():

int endX = startX + (int)Math.round(Math.cos(Math.toRadians(angle)) * length);
int endY = startY + (int)Math.round(Math.sin(Math.toRadians(angle)) * length);

You may not notice any difference in your drawing on screen, but lost precision can add up to visible glitches.

Upvotes: 1

glee8e
glee8e

Reputation: 6419

You are a victim of operator precedency. You need

int endX = startX + (int) (Math.cos(Math.toRadians(angle)) * length);
int endY = startY + (int) (Math.sin(Math.toRadians(angle)) * length);

Upvotes: 2

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