I can't know the exact reason for this, but this is my educated guess:

  A 'transform' identifier probably uses internally a transformation
matrix, and when you apply a matrix transformation to the light, the area
light ignores it because the transformation matrix might transform it in
ways which make it invalid (ie. not rectangular). Direct 'translate' and
'rotate' commands are "optimized" so that they are applied to the area
light appropriately.

  If this is the case, there may be two possible solutions (both of which
require enhancing the source code of povray):

  1) When applying a matrix transfomration to the area light, check if it
will keep the area light rectangular, and if so, apply it, else don't (and
issue a warning).

  2) Enhance the 'transform' identifier so that it internally knows what
types of transforms have been added to it, so these can be easily checked
or applied separately as needed.

-- 
                                                          - Warp

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