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ctx.arcTo Bug #56

apitaru opened this Issue Nov 6, 2012 · 2 comments


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apitaru commented Nov 6, 2012

While trying to port a few vector drawings into ejecta, I noticed that arcTo() is not drawing predictably.

A simple example is here: http://www.html5canvastutorials.com/tutorials/html5-canvas-rounded-corners/

In this example Ejecta will not draw the curve at all, making me thing that in arcToX1 "if( mm < 1.0e-8 || radius == 0 )" is inaccurately returning true. But more sophisticated drawings will cause it to shoot lines in unpredictable directions, so I think one of the base variables might be wrong.

I also looked at the original code that you mention arcToX1 is taken from ( http://code.google.com/p/fxcanvas/source/search?q=1.0e-8&origq=1.0e-8&btnG=Search+Trunk ), and I wonder if your "cp" variable is getting the right values from:

EJVector2 cp = EJVector2ApplyTransform(EJVector2Make(x1, y1), CGAffineTransformInvert(transform));

Sorry I can't be more descriptive - I'm humbled by the math there : )


@apitaru apitaru closed this Nov 6, 2012

@apitaru apitaru reopened this Nov 8, 2012

apitaru commented Nov 8, 2012

(btw - a few days ago i created a duplicate issue. github doesn't allow to delete them, so i'm "recycling" it with a new topic. sorry about that. never again.

@phoboslab phoboslab closed this in 231d8aa Nov 9, 2012


phoboslab commented Nov 9, 2012

Thanks for reporting!

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