[cairo] The right approach to projective transformations

Behdad Esfahbod behdad.esfahbod at gmail.com
Mon Aug 30 14:16:26 PDT 2010

On 08/28/10 12:05, James Cloos wrote:
>>>>>> "MB" == Maarten Bosmans <mkbosmans at gmail.com> writes:
> MB> However, how much time in a typical pixman/cairo run is spend in
> MB> matrix operations? Probably not that much compared to compositing.
> I suppose I was visualizing matrix mults each time anything is placed or
> drawn, to convert to device units.  Perhaps that exaggerates things? :)
> If it is infrequent, then using and array of nine values instead of a
> well-aligned array of sixteen values would be OK.

I think if we are doing this projective thing, we should finally switch to an
opaque transformation struct.  This allows for the transformation to be
intelligently caching.  Cache the inverse, cache the determinant, cache
whether it's an integer translation only, etc.


> -JimC

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