How to properly create path art object, please help

Question

Hello there,
I have a vector of AIRealPoint , each point is actual X, Y coordinate of the stroke. I need to create path art object out of this vector.
I'm  somehow confused how to correctly construct segments array form the given AIRealPoints, my goal is to have single path object where count of segments is equal to count of AIrealPoints first and last points are anchors. SDK documenation is not really helping here...
Please, take a look at the code snippet, it seems I'm doing something wrong with in and out params of segment , in any case I fail to create simple path object ....
ASErr CretaeVectorPathTest2(vector<AIRealPoint>& stroke)
AIArtHandle artHandle;
ASErr result = kNoErr;
try {
  AIRealPoint start;
  long lngStrokeLength = stroke.size()-1;
  AIArtHandle lineHandle = NULL;
  AIErr error = sAIArt->NewArt( kPathArt, kPlaceAboveAll, NULL, &lineHandle );
  if ( error ) throw( error );
  error = sAIPath->SetPathSegmentCount( lineHandle, lngStrokeLength );
  if ( error ) throw( error );
  AIPathSegment *segment = new AIPathSegment[lngStrokeLength];
  // This is a first point of the path
  segment[0].p.h = stroke[0].h;
  segment[0].p.v = stroke[0].v;
  segment[0].in = segment[0].out = segment[0].p;
  segment[0].corner = true;
  for(inti=1 ;i< lngStrokeLength-1;i++)
   segment[i].p.h = stroke[i].h ;
   segment[i].p.v = stroke[i].h ;
   // NOT GOOD!!!
   segment[i].in.h  = stroke[i-1].h ;
   segment[i].in.v  = stroke[i-1].v ;
   segment[i].out.h  = stroke[i+1].h;
   segment[i].out.v  = stroke[i+1].v;
   segment[i].corner = false;
// NOT GOOD!!!
  // This is a last point of the path
  segment[lngStrokeLength].p.h = stroke[lngStrokeLength].h;
  segment[lngStrokeLength].p.v = stroke[lngStrokeLength].v;
  segment[lngStrokeLength].in = segment[lngStrokeLength].out = segment[lngStrokeLength].p;
  segment[lngStrokeLength].corner = true;
  error = sAIPath->SetPathSegments( lineHandle, 0, lngStrokeLength, segment );
  if ( error ) throw( error );
  error = sAIPath->SetPathClosed( lineHandle, false );
  if ( error ) throw( error );
// apply color width etc.
  AIPathStyle style;
  error = sAIPathStyle->GetPathStyle( lineHandle, &style );
  if ( error ) throw( error );
  style.strokePaint = true;
  style.stroke.color.kind = kFourColor;
  style.stroke.color.c.f.cyan = 0;
  style.stroke.color.c.f.magenta = 0;
  style.stroke.color.c.f.yellow = 0;
  style.stroke.color.c.f.black = 100;
  style.stroke.width = 0.75;
  style.stroke.dash.length = 0;
  delete[] segment;
  error = sAIPathStyle->SetPathStyle( lineHandle, &style );
  if ( error ) throw( error );
catch (ai::Error& ex) {
  result = ex;
return result;
Thanks,
David

Answer 1

As for beziers, Illustrator uses cubic beziers which are fairly straight forward (thank goodness!). Here's a lift from Wikipedia's Bezier entry:
This image is pretty good at demonstrating how AI's bezier segments work. In the animation, the moving point has two lines sticking off it, ending with two points. If P3 was an AISegment, the left-hand blue point would be in and the right-hand point would be out. If we were to translate the state of the animation in its last frame into AI code, you'd basically have something like this:
AISegment segment1, segment2;
segment1.p = p0;
segment1.in = p0;
segment1.out = p1;
segment2.in = p2;
segment2.p = p3;
segment.out = p3;
Note that this would imply any line that continues beyond either end point isn't a smooth beizer curve (i.e. the curve is limited to between these points). That effectively makes them corner points (I think). Also, the line formed by linking in & p or out & p is the tangent to the curve at p, which I think you can make out from from the animation.
Another way to get a feel for this is to use the pen tool to draw a line with a few segments. If you then pick the sub-select tool (white selection arrow, not black selection arrow) and select individual points on the curve, you'll see when you do that two 'anchors' jut out from each point. Those are the in & out for that point on the curve.
Its all a little confusing because technically, a bezier segment between p & q would be p, p.out, q.in & q. (four vertices). To avoid repeating information, and keep it simple for non-beziers, AI's segments are still the vertices. So if you wanted to make the nth segment a beizer, you'd need n & n+1 from AI's path, and you'd modify two-thirds of each AISegment (p, out from n & in, p from n+1).
I hope that helps, but if you have any further questions, feel free to ask! If you need to do anything fancy with beziers, there are some helpful utilites in AIRealBezier.h.