On Tue, 4 Jan 2005, Ian Ollmann wrote:
> I believe the problem is that we are flip flopping between vertical
> first and horizontal first in the resampling passes, based on the area
> of the intermediate representation. The horizontal and vertical passes
> are very different speed on Panther. Vertical is much slower. The speed
> difference is greatly improved on Tiger. We used the one with the
> larger intermediate area. It may be we should reexamine that decision.
>
IIRC, Graphics Gems recommends to do that pass first which reduces the
number of pixels the most (for speed reasons). If I am not mistaken, the
theoretical accuracy (if you were to compute with infinite precision) does
not suffer from such a choice, at least for some common resampling
filters. With finite precision it does make a tiny difference, I think.
Does the API provide means to select a speed/accuracy balance? It might be
better to leave this decision to the programmer on a case by case basis
rather than make it statically in the library. He knows better if the
results are ephemeral eye candy or precious sample data of an expensive
experiment.
Holger
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