Foreshortening is entirely handled in the projection parameters - ie is intrinsic to them. so you don't need to do anything for that.

Thanks for clearifying that Ron, indeed I was under the assumption foreshortening had to be applied, however reading up on orthographic projection it makes a a lot of sense it is the result of it.

So since the dreaded 'm' word has come up, it seems I've managed to calculate the camera position for all zooms using a fixed range of 190 meters. In each render the camera is looking at the center of mass of the lod (0,0,8) and uses the same orthographic scale and no offsets (more on that in a bit). On a sidenote, in gmax I noticed the camera looks at a position slightly above the lod, would be interesting to know what the look at point is in studio max.

Now onto what seems crucial to get right: the orthographic scale of the camera, and closely related the x & y camera offsets. Blender describes the scale as being 'similar to zoom', and

online I found the following explanation;

The Orthographic Scale factor represent the maximum dimension (in scene units) of the portion of space captured from the camera.

Or to put that yet another way, when the camera is looking straight down to the ground the dimensions of the surface area captured by the camera correspond to the scaling factor (and this holds true irrespective of camera height location).

So if for example an orthographic scale of 32 is used (as I had done initially for zoom5 as it seemed to make some intuitive sense) and the camera looks down, the area captured by the camera measures 32 x 32 meters. However by trail-and-error I arrived at the following settings for the zoom5 render. Also note the offsets to manoeuvre the model to the topleft corner. The offsets use a 0..1 range whereby an offset of 1 moves the camera by the scale value along the axis, thus I reckon it should be viable to use them as viewport stop values.

And side-by-side comparison.

Also made an interesting find playing with some of the numbers in Ron's article. Here's the relevant numbers for zoom 5;

Level | Zoom x | Rel Range | Equiv Range m | Pixel in m |

Z5 | 146 | 1 | 26.1 | 0.102 |

The finding is that if an orthographic scale of 26.1 is used, i.e. the Equivalent Range in meters, the 16x16x16 model fits snuggly into the camera viewport heightwise (provided no offsets are used, and the camera is looking at the center of mass). I'm intrigued the corresponding Relative Range of 1 seems to indicate some 'true' scale, and is echoed by the heightwise fit of the model relative to the camera exclusivly.

So yeah all things considered the orthographic scale seems to be quite crucial indeed, and I stronlgy suspect it can be calculated using the known camera positions and render dimensions but alas, my maths game is not

*that* strong.