Sat, 23 Feb 2008 04:02:58 +0100 "jf barraud" <jf.barraud@...400...> kirjoitti:
I have been looking at other effects that do not render properly when transformed, but I need help about the code: can someone help me with "area_enlarge"? -is the area in display coordinates? -how to interpret the filter parameters (for instance scale for displacement map) in these coordinates?
As it stands, area_enlarge works in display coordinates. It is supposed to take in bounding box of wanted output image and to enlarge that, so that it contains everything needed to render that area. It does not need to take into account the filter effects area.
In displacement map, for instance, the possible pixels required to render any pixel lie inside a rectangle (in filter coordinates). The to-be-rendered pixel lies in the centre of that rectangle and edge lengths are determined by scale. Transform that rectangle into display coordinates. By taking the greatest extents of the transformed rectangle, you can determine how far in display coordinates required pixels can lay from the to-be-rendered pixel.