[Bf-committers] Movie distortion algorithm

[Jonathan Merritt]

Reading that paper (Vass and Perlaki), they present a very good solution.
 If you're running the inverse transformation on a sequence of frames, all
of which have the same distortion parameters, then just compute the inverse
transformation once ("slow"), and cache the result.  Then do a look-up
using either exact values or some kind of fast interpolation for all of
your movie frames.

They also describe using Newton's method to compute the (xd, yd) => (x,y)
transformation, as I suggested.  Since these guys have already looked at
this problem, I suspect that the algebraic inverse transformation is
probably very long and painful.

Even if your distortion parameters are varying, you could also speed up the
process by using the solution from the previous frame as the staring point
for your Newton iteration of the next frame.

On Mon, Apr 16, 2012 at 4:06 PM, Dan Eicher <dan at trollwerks.org> wrote:
>
>> These guys describe a fast preview mode (if that's the problem):
>>
>> http://www.vassg.hu/pdf/vass_gg_2003_lo.pdf
>>
>> ...not that I understand the math behind it.
>>
>> Dan
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