feat(annotation) Add default annontation properties

[chrisj]

add line length property

This came up during a meeting that the scale bar has been used as a rough measure of the size of features in datasets. I was thinking we should have a better way to measure distance and the line annotation is already a tool that has most of the requirements.

I think it would also make sense to add additional properties for other types such as ellipsoid volume and semi axis lengths, bounding box volume and dimensions.

I am currently making assumptions to cast float32array to a vec3 and there might be a better method of using the globalCoordinateSpace.

[jbms]

Overall I like this idea, thanks!

Originally some default properties like length, volume, etc. were shown for annotations but that support was left out when I refactored some years ago to support more than 3 dimensions.

The logic related to scales will need to change ---- the coordinate space of the annotation is not necessarily 3d and doesn't necessarily directly correspond to the global coordinate space, so some coordinate transforms will need to happen, and units taken into account also.

[jbms]

This is still not correct --- you need to transform the scales, taking into account the various affine transforms that apply, similar to what is done here:

neuroglancer/src/ui/annotations.ts

Line 1073 in 5898236

function getMousePositionInAnnotationCoordinates(

[jbms]

This shouldn't always be nanometers --- it should take into account the units set in the coordinate space.

If all dimensions have the same base unit, e.g. meter, then you could just choose an appropriate scale automatically as in the scale bar.

If there are mixed units, e.g. meters and seconds, then probably just don't display the length at all.

[chrisj]

I updated it to use globalCoordinateSpace.units and using ALLOWED_UNITS from scale_bar.ts to disable the property. If any unit is a non-length unit, it won't add the property. Also cleaned up the code

[jbms]

The points stored in the annotation are in the "model" coordinate space. There is an affine transform that maps between that coordinate space and the concatenation of the layer-local and global coordinate spaces.

The lengths could be computed either in the "model" coordinate space or in the global coordinate space,.or maybe both, but right now you are using the untransformed points in the model coordinate space with the global coordinate space scales, which is not correct.

[chrisj]

Hi Jeremy, I am now passing in the positions from visitTransformedAnnotationGeometry to the defaultAnnotationProperties function. I think I could clean it up a bit if visitTransformedAnnotationGeometry was changed from being a function that uses callbacks to instead returning an array of [layerPosition, isVector].

Does this fix the coordinate space issue? It I'm still using global scales/units. this.localCoordinateSpace.value.scales, this.localCoordinateSpace.value.units show empty. When would it have a value?

Here is an example where i can see the length increase when I give the x dimension a 10x scale.