As "brick after brick" facades are quite long to render I use now for remote
buildings simple panes with an image_map.

It's way quicker and give enough quality for remote background objects.

BUT there are some traps to take care.

The image will be mapped on a rectangular facade, so it has to be also
perfectly rectangular. The perspective will be given by the angle of the
surface on which you have mapped the rectangular image

You get this when the line joining the camera position to the "look at"
point is perpendicular to the wall.
But then, you get a face view which will look odd if the facade is seen from
a sharp angle. (Windows and door sides)

For them, the best is to use the orthographic camera which keep the lines
parallel (no vanishing point) whatever is the angle.

But you must make a correction, making the image wider for compesation of
the view angle a bit like for an anamorhosis (http://www.anamorphosis.com/)

On the code below I just take care of the lateral angle.

#declare xLoc = xWall/2;
#declare zLoc = 5200;

#declare xFoc = xWall/2;

#declare yLocFoc = yWall*2;

#declare angleNorm = atan((xLoc-xFoc)/zLoc);
#declare corpes = cos(angleNorm );

////////////////////////////////////////CAMERA
///////////////////////////////////////
camera {  //  Camera StdCam
  orthographic
  location  <  xLoc,     yLocFoc,       -zLoc>
  look_at   <  xFoc,     yLocFoc,      0>
  angle        20

  right x*  corpes * 1280/1024
  up y

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