OpenGL circle rotation
- by user350632
I'm using following code to draw my circles:
double theta = 2 * 3.1415926 / num_segments;
double c = Math.Cos(theta);//precalculate the sine and cosine
double s = Math.Sin(theta);
double t;
double x = r;//we start at angle = 0
double y = 0;
GL.glBegin(GL.GL_LINE_LOOP);
for(int ii = 0; ii < num_segments; ii++)
{
float first = (float)(x * scaleX + cx) / xyFactor;
float second = (float)(y * scaleY + cy) / xyFactor;
GL.glVertex2f(first, second); // output Vertex
//apply the rotation matrix
t = x;
x = c * x - s * y;
y = s * t + c * y;
}
GL.glEnd();
The problem is that when scaleX is different from scaleY then circles are transformed in the right way except for the rotation.
In my code sequence looks like this:
circle.Scale(tmp_p.scaleX, tmp_p.scaleY);
circle.Rotate(tmp_p.rotateAngle);
My question is what other calculations should i perform for circle to rotate properly when scaleX and scaleY are not equal?
