draw ellipses

[Gregory]

How can I draw ellipses?

[Cierpliwy]

SFML doesn't support such primitives, or am i wrong?

So I would try to draw them using fragment shader if it's not a problem for you.

[Laurent]

Create a circle shape and scale it in one direction to make it an ellipse.

[Gregory]

the problem is that i'm make this for my paint program, i want to know de math for this

[Laurent]

There's no math.

Code: [Select]

sf::Shape ellipse = sf::Shape::Circle(...);
ellipse.SetScale(2, 1);

But if you're doing a paint program maybe you should manipulate individual pixels directly?

[Gregory]

yes, i'm manipuling the pixels directily, for this, i want to know de math for make elipse with 4 points, X1,Y1,X2,Y2

[Nexus]

Look at http://en.wikipedia.org/wiki/Ellipse or use google.

An ellipse is the set of all points, where the sum of distances between the point on the ellipse and each of two other specific points (focus) remains constant.

[Tomhet]

//math for ellipse

#include<cmath>



#define PI 3.1415926535898

float radius_x=50;
float radius_y=20;
unsigned short quality=70;

sf::ConvexShape ellipse;
    ellipse.setPointCount(quality);

for(unsigned short i=0;i<quality;++i){
    float rad=(360/quality*i)/(360/PI/2);
    float x=cos(rad)*radius_x;
    float y=sin(rad)*radius_y;

    ellipse.setPoint(i,sf::Vector2f(x,y));
};

ellipse.setPosition(100,100);

[Hiura]

If you're looking for more general curves, you can have a look at sftools::Curve & sftools::CurveInfo here http://mantognini.github.io/sftools/public/doc/html/annotated.html. The code is hosted on github here https://github.com/mantognini/sftools