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PODrawing Smooth Curves - Methods Needed
 

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    <p>How do you smooth a set of points in an iOS drawing app WHILE MOVING? I have tried UIBezierpaths but all I get are jagged ends where they intersect, when I just shift the points 1,2,3,4 - 2,3,4,5. I have heard of spline curves and all the other types. I am quite new to iPhone programming and do not understand how to program it in my quartz drawing app. A solid example would be greatly appreciated, I have spent weeks running in circles and I can never seem to find any iOS code for this task. Most of the posts just link to a java simulation or pages on wikipedia about curve fitting which does nothing for me. Also I do not want to switch to openGL ES. I hope someone can finally provide code to answer this circulating question.</p> <hr> <p>This was my code for the UIBezierPath which left edges at intersection///</p> <p>UPDATED TO AN ANSWER BELOW</p> <pre><code>#define VALUE(_INDEX_) [NSValue valueWithCGPoint:points[_INDEX_]] #define POINT(_INDEX_) [(NSValue *)[points objectAtIndex:_INDEX_] CGPointValue] - (UIBezierPath*)smoothedPathWithGranularity:(NSInteger)granularity { NSMutableArray *points = [(NSMutableArray*)[self pointsOrdered] mutableCopy]; if (points.count &lt; 4) return [self bezierPath]; // Add control points to make the math make sense [points insertObject:[points objectAtIndex:0] atIndex:0]; [points addObject:[points lastObject]]; UIBezierPath *smoothedPath = [self bezierPath]; [smoothedPath removeAllPoints]; [smoothedPath moveToPoint:POINT(0)]; for (NSUInteger index = 1; index &lt; points.count - 2; index++) { CGPoint p0 = POINT(index - 1); CGPoint p1 = POINT(index); CGPoint p2 = POINT(index + 1); CGPoint p3 = POINT(index + 2); // now add n points starting at p1 + dx/dy up until p2 using Catmull-Rom splines for (int i = 1; i &lt; granularity; i++) { float t = (float) i * (1.0f / (float) granularity); float tt = t * t; float ttt = tt * t; CGPoint pi; // intermediate point pi.x = 0.5 * (2*p1.x+(p2.x-p0.x)*t + (2*p0.x-5*p1.x+4*p2.x-p3.x)*tt + (3*p1.x-p0.x-3*p2.x+p3.x)*ttt); pi.y = 0.5 * (2*p1.y+(p2.y-p0.y)*t + (2*p0.y-5*p1.y+4*p2.y-p3.y)*tt + (3*p1.y-p0.y-3*p2.y+p3.y)*ttt); [smoothedPath addLineToPoint:pi]; } // Now add p2 [smoothedPath addLineToPoint:p2]; } // finish by adding the last point [smoothedPath addLineToPoint:POINT(points.count - 1)]; return smoothedPath; } - (PVPoint *)pointAppendingCGPoint:(CGPoint)CGPoint { PVPoint *newPoint = [[PVPoint alloc] initInsertingIntoManagedObjectContext:[self managedObjectContext]]; [newPoint setCGPoint:CGPoint]; [newPoint setOrder:[NSNumber numberWithUnsignedInteger:[[self points] count]]]; [[self mutableSetValueForKey:@"points"] addObject:newPoint]; [(NSMutableArray *)[self pointsOrdered] addObject:newPoint]; [[self bezierPath] addLineToPoint:CGPoint]; return [newPoint autorelease]; if ([self bezierPath] &amp;&amp; [pointsOrdered count] &gt; 3) { PVPoint *control1 = [pointsOrdered objectAtIndex:[pointsOrdered count] - 2]; PVPoint *control2 = [pointsOrdered objectAtIndex:[pointsOrdered count] - 1]; [bezierPath moveToPoint:[[pointsOrdered objectAtIndex:[pointsOrdered count] - 3] CGPoint]]; [[self bezierPath] addCurveToPoint:CGPoint controlPoint1:[control1 CGPoint] controlPoint2:[control2 CGPoint]]; } } - (BOOL)isComplete { return [[self points] count] &gt; 1; } - (UIBezierPath *)bezierPath { if (!bezierPath) { bezierPath = [UIBezierPath bezierPath]; for (NSUInteger p = 0; p &lt; [[self points] count]; p++) { if (!p) [bezierPath moveToPoint:[(PVPoint *)[[self pointsOrdered] objectAtIndex:p] CGPoint]]; else [bezierPath addLineToPoint:[(PVPoint *)[[self pointsOrdered] objectAtIndex:p] CGPoint]]; } [bezierPath retain]; } return bezierPath; } - (CGPathRef)CGPath { return [[self bezierPath] CGPath]; } </code></pre> <p><img src="https://i.stack.imgur.com/hS7wY.png" alt="phone screen"></p>
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    1. COCan you show us the jagged ends?
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    2. COPlease look above for the UIBezierPath code.
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    3. COthere is a Sample code from apple called QuartzDemo
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