void drawArrow(Vector2f const& from, Vector2f const& to, Color3f const& color, float width) {
Vector2f direction((to-from).normalize()*width*0.5f);
Vector2f normal(direction.y_, -direction.x_);
glBlendFunc(GL_ONE, GL_ONE);
glLineWidth(width);
glBegin(GL_TRIANGLES);
(color*0.5f).gl3f();
glVertex2f(from.x_,from.y_);
color.gl3f();
glVertex2f(to.x_-normal.x_,to.y_-normal.y_);
glVertex2f(to.x_+normal.x_,to.y_+normal.y_);
glVertex2f(to.x_+direction.x_*3.f,to.y_+direction.y_*3.f);
glVertex2f(to.x_+normal.x_*2.f,to.y_+normal.y_*2.f);
glVertex2f(to.x_-normal.x_*2.f,to.y_-normal.y_*2.f);
glEnd();
}
