Is there a way to create sheared orthographic camera? I need to offset
camera location along *both* X and Y axes (image plane is coplanar with XY),
while leaving camera target (look_at) intact, and have every camera ray
skewed accordingly.

If I offset camera location just along a single axis, I do have the desired
effect. But if I offset along both axes, the image gets distorted badly --
vertical lines are OK, while horizontal lines (i.e. parallel to X axis of
the image) lines get unwanted skew...

In orher words, suppose I have two L-shapes, one strictly above the other,
and render them using orthographic "top" projection (in my coordinate
system, that means "along Z axis"); I get something like this:
  ____
  |
  |

So far, so good. Now I offset camera location along both X and Y axes and
render again; I get something like this (the actual skew is lesser, but you
should get the idea):

   /
  /   /
  |  /
  |  |
     |

while I wanted something like this:

  ____
  |  ____
  |  |
     |


The actual camera definition I used is this (remember that image plane is
coplanar with XY):

camera { orthographic
  location <-60,84,75>
  right x*64
  up -y*48
  look_at <-68,76,0>
  direction <-8,-8,-74>
  sky -y
}

Of course, I could make a patch which would do what I wanted... But I would
like to be sure that that could not be achieved with plain vanilla SDL. So,
any ideas?..

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