On Thu, Jul 30, 2015 at 6:07 AM Gurjot Singh Bhatti <[email protected]> wrote:
> On 24 July 2015 at 22:43, Dan Dennedy <[email protected]> wrote: > > Another challenge is to figure out how to represent MLT's Catmull-Rom > spline > > curves using the API's Bezier curve functions. I do not have a solid > answer > > for that, but I did bookmark this link a while ago: > > > http://www.antigrain.com/__code/include/agg_curves.h.html#catrom_to_bezier > > I have not fully analyzed that yet, and I would need to study the topic > more > > to do something with it. > > Can I get these catmull-rom points from the mlt_keyframe_spline > keyframe somehow (MLT API)? > No, because the beauty of Catmull-Rom is that there are no additional control points. It is automatically the smoothest curve fitted to a set of data points: your keyframes' time position and value. We just need to figure out how to emulate this using a Bezier curve, but I have not been able to look into this deeply. I did a Google search on "simulate catmull-rom using bezier." A search result led me to this nice article: http://schepers.cc/getting-to-the-point In it he refers to the same Anti-Grain Geometry code I referred to. :-) However, it looks like he also pulled it together into a concise, more readable javascript version. Also, see this comment in the MLT code about how additional points before the first and after the last are needed: https://github.com/mltframework/mlt/blob/master/src/framework/mlt_property.c#L1072 The code following that (mlt_property_interpolate) handles transitions between different types of interpolation.
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