CGPathRef / Bezier Curves in OpenGL-ES - opengl-es

Question

I am considering porting an iPhone project from core animation to OpenGL-ES.
I need to render a button that is constructed from CGPathRef s.
But it seems that GL has no provision for Bezier Curves.
Can anyone provide some code that renders a Bezier Curve in GL?

Answer 1

This will accept a series of points to draw a rounded bezier line. It must use point sprites. If you send it a line of three points, and a number of point sprites to draw, it will create a bezeir line. The code is based of something I found somewhere, but I cannot remember where.
It requires:
CGPoint origin - First Point
CGPoint control - Mid Point
CGPoint destination - End Point
int segments - Number of points to render.
To calculate the number of points, I use:
count = MAX(ceilf(sqrtf(([[currentStroke objectAtIndex:i+2] CGPointValue].x - [[currentStroke objectAtIndex:i] CGPointValue].x)
* ([[currentStroke objectAtIndex:i+2] CGPointValue].x - [[currentStroke objectAtIndex:i] CGPointValue].x)
+ ((invertedYThirdCoord - invertedYBegCoord) * (invertedYThirdCoord - invertedYBegCoord))) / 2), 1)*4;
Anyway, the code (in C++):
CGPoint vertices[segments];
CGPoint midPoint;
float x, y;
float t = 0.0;
for(int i = 0; i < (segments); i++)
{
x = pow(1 - t, 2) * origin.x + 2.0 * (1 - t) * t * control.x + t * t * destination.x;
y = pow(1 - t, 2) * origin.y + 2.0 * (1 - t) * t * control.y + t * t * destination.y;
vertices[i] = CGPointMake(x, y);
t += 1.0 / (segments);
}
midPoint = CGPointMake(x, 288 - y);
glVertexPointer(2, GL_FLOAT, 0, vertices);
glDrawArrays(GL_POINTS, 0, segments);
Following this render as normal.