Added field size property to OrthographicCamera

[vincentmarchetti]

The PerspectiveCamera has a property fieldOfView as illustrated in the figure in https://github.com/IIIF/3d/blob/main/temp-draft-4.md#lights . In the limiting case of moving a PerspectiveCamera out to infinite distance and narrowing the fieldOfView to 0, giving an OrthographicCamera, we need a replacement property which is a linear dimension, for example "3" representing 3 meters. By analogy with the fieldOfView definition, this linear dimension would be the vertical dimension of the viewport in the orthographic projection.

[JulieWinchester]

I think I agree with this, although like I said in #2288 orthographic cameras should definitely be able to have a position and so should not need to be moved out to infinite distance. But orthographic cameras probably need something to determine the distance between top and bottom frustum planes.

[azaroth42]

Eds agree -- add height to the OrthographicCamera to mirror the vertical field of view on PerspectiveCamera

[vincentmarchetti]

There is a name collision between this property of an OrthographicCamera resource and a property of same name in several resources types defined in Presentation 3 -- for example. Canvas. This naming does not cause any problems in, for example, the manifesto javascript library. Is this choice of names intentional for that reason?

[kirschbombe]

If term collision is an issue, maybe viewHeight?

[azaroth42]

height of a Canvas or content resource (like an image or video) is an abstract "height" rather than a number of pixels.

That said, if we want to use the Value format for this that has both numeric value and unit, it would need to be different as height is explicitly just the numeric value.

[vincentmarchetti]

Turns out the name collision does cause problems in the Typescript (strongly typed) language implementation of manifesto.Could be resolved with tinkering of the manifesto code, which is not really an issue for the editors to consider. However, it seems that in the 2D presentation API, Height , and WIdth, are fundamental properties of a number of the resource types, all with related meaning. It may not be a good idea to give a 3D resource a property of that name but with incompatible meaning.