Abid Hussain - 8 months ago 63

Objective-C Question

I'm drawing a graph in my application. My problem is that I want to draw line joining vertex points as curves. Currently I'm drawing them with

`UIBezierPath`

`addLineToPoint:`

`UIBezierPath`

Cubic curve:

`addCurveToPoint:controlPoint1:controlPoint2:`

Quadratic curve:

`addQuadCurveToPoint:controlPoint:`

But problem is that I don't have control points. All i have is two end points. Neither I found a method/formula to determine control points. Can anyone help me here? I will appreciate if someone can suggest some alternative...

Answer

SO I found a work around based on @Fogmeister's answer.

```
UIBezierPath *path = [UIBezierPath bezierPath];
[path setLineWidth:3.0];
[path setLineCapStyle:kCGLineCapRound];
[path setLineJoinStyle:kCGLineJoinRound];
// actualPoints are my points array stored as NSValue
NSValue *value = [actualPoints objectAtIndex:0];
CGPoint p1 = [value CGPointValue];
[path moveToPoint:p1];
for (int k=1; k<[actualPoints count];k++) {
NSValue *value = [actualPoints objectAtIndex:k];
CGPoint p2 = [value CGPointValue];
CGPoint centerPoint = CGPointMake((p1.x+p2.x)/2, (p1.y+p2.y)/2);
// See if your curve is decreasing or increasing
// You can optimize it further by finding point on normal of line passing through midpoint
if (p1.y<p2.y) {
centerPoint = CGPointMake(centerPoint.x, centerPoint.y+(abs(p2.y-centerPoint.y)));
}else if(p1.y>p2.y){
centerPoint = CGPointMake(centerPoint.x, centerPoint.y-(abs(p2.y-centerPoint.y)));
}
[path addQuadCurveToPoint:p2 controlPoint:centerPoint];
p1 = p2;
}
[path stroke];
```

Source (Stackoverflow)