Re: [Openexr-devel] DisplayWindow example images - -1, -1 display window origin?

[Paul Miller]

On 8/1/2011 10:17 PM, Florian Kainz wrote:
> OpenEXR allows negative coordinates for the display window and data window.
> OpenEXR also does not prescribe any particular spatial relationship between
> the data window and the display window. The two windows will usually
> overlap, but they don't have to. Some of the t??.exr files are meant to
> test application behavior for the non-overlapping case.

Florian - you say OpenEXR doesn't prescribe any particular spatial 
relationship between the data window and the display window. I can 
understand a data window that does not overlay the display window (for 
say a CG object that has gone out of frame, but who's data could still 
be used to generate shadows or something else in-frame - I'm not a 
compositor so I'm guessing here). Can you provide an example of a 
situation where the data/display windows do not have this kind of 
spatial relationship?

That aside, Silhouette does not yet have the concept of a data window or 
ROI. Unfortunately I have to clip the data to the display when I read 
the image. Is there a way to read the intersection of the data/display 
windows using some combination of the framebuffer parameters and 
readPixels() range, without resorting to a line-by-line read?

Many thanks for your advice!