VB/WinAPI/Graphics, Is there a bezierDDA API?

Is there a bezierDDA API?

Author	Message
Aristotelis Charalampaki #1 / 5	Is there a bezierDDA API? Hi all, I was wondering if there is a kind of "BezierDDA" API, which will enumerate all points in a bezier curve, just like LineDDA. If it exists I cannot find it. Any clues? Any alternatives maybe? TIA Aristotelis
Sun, 01 May 2005 01:54:02 GMT

Mike D Sutto #2 / 5	Is there a bezierDDA API? Quote: > I was wondering if there is a kind of "BezierDDA" API, which will enumerate > all points in a bezier curve, just like LineDDA. If it exists I cannot find > it. Any clues? Any alternatives maybe? Not really, the DDA algorithm works by exploiting the symmetrical and (Excuse me for pointing out the obvious) linear properties of a line which of course don't work in the same way for a curve. You can however use a cubic function to extrapolate points from the curve and run a LineDDA on each segment. Hope this helps, Mike -- EDais -- - Microsoft Visual Basic MVP - WWW: Http://EDais.earlsoft.co.uk/
Sun, 01 May 2005 00:33:58 GMT

Aristotelis Charalampaki #3 / 5	Is there a bezierDDA API? Sorry If I did not make myself clear; I was hoping to avoid the math stuff! I dont want to draw the curve myself, I just want the points of the curve with a "callback" function, so that after, say, 100 points I would connect the two ends with a straight line. The smaller the interval, the better the approximation. The points would be "connected" in a DXF file that I have to create. Something like the Bresenham algorithm but for a bezier curve. I am sure that this API exists. Maybe it is not documented, but if there is an API for the drawing of these curves, then there must be an api that enumerates the points. TIA, Aristotelis Quote: > > I was wondering if there is a kind of "BezierDDA" API, which will > enumerate > > all points in a bezier curve, just like LineDDA. If it exists I cannot > find > > it. Any clues? Any alternatives maybe? > Not really, the DDA algorithm works by exploiting the symmetrical and > (Excuse me for pointing out the obvious) linear properties of a line which > of course don't work in the same way for a curve. You can however use a > cubic function to extrapolate points from the curve and run a LineDDA on > each segment. > Hope this helps, > Mike > -- EDais -- > - Microsoft Visual Basic MVP - > WWW: Http://EDais.earlsoft.co.uk/
Mon, 02 May 2005 03:40:36 GMT

Mike D Sutto #4 / 5	Is there a bezierDDA API? Quote: > Sorry If I did not make myself clear; I was hoping to avoid the math stuff! It's not too difficult to find the code online and convert it to VB - Most mathematics stays pretty much the same between the two languages. Quote: > I dont want to draw the curve myself, I just want the points of the curve > with a "callback" function, so that after, say, 100 points I would connect > the two ends with a straight line. The smaller the interval, the better the > approximation. The points would be "connected" in a DXF file that I have to > create. Something like the Bresenham algorithm but for a bezier curve. The curve is most likely drawn as a series of line segment each in turn draw with a Bresenham or similar routine. Quote: > I am sure that this API exists. Maybe it is not documented, but if there is > an API for the drawing of these curves, then there must be an api that > enumerates the points. Have a look at GDI32.dll in the dependency walker, you'll see that the only *DDA function is LineDDA(). What you can do though is convert the output of the PolyBezier() API to a path then get the line segments from that. I did some digging and found this article which you may find useful: <watch for wrap> http://msdn.microsoft.com/library/en-us/dngdi/html/msdn_hittest2.asp </watch for wrap> Hope this helps, Mike -- EDais -- - Microsoft Visual Basic MVP - WWW: Http://EDais.earlsoft.co.uk/
Mon, 02 May 2005 03:45:24 GMT

Aristotelis Charalampaki #5 / 5	Is there a bezierDDA API? Interesting article, I think it will do. Thanx mike! Aristotelis Quote: > > Sorry If I did not make myself clear; I was hoping to avoid the math > stuff! > It's not too difficult to find the code online and convert it to VB - Most > mathematics stays pretty much the same between the two languages. > > I dont want to draw the curve myself, I just want the points of the curve > > with a "callback" function, so that after, say, 100 points I would connect > > the two ends with a straight line. The smaller the interval, the better > the > > approximation. The points would be "connected" in a DXF file that I have > to > > create. Something like the Bresenham algorithm but for a bezier curve. > The curve is most likely drawn as a series of line segment each in turn draw > with a Bresenham or similar routine. > > I am sure that this API exists. Maybe it is not documented, but if there > is > > an API for the drawing of these curves, then there must be an api that > > enumerates the points. > Have a look at GDI32.dll in the dependency walker, you'll see that the only > *DDA function is LineDDA(). > What you can do though is convert the output of the PolyBezier() API to a > path then get the line segments from that. I did some digging and found > this article which you may find useful: > <watch for wrap> > http://msdn.microsoft.com/library/en-us/dngdi/html/msdn_hittest2.asp > </watch for wrap> > Hope this helps, > Mike > -- EDais -- > - Microsoft Visual Basic MVP - > WWW: Http://EDais.earlsoft.co.uk/
Mon, 02 May 2005 16:42:07 GMT

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