I’m a newbie in COLLADA. I need would like to include landmarks in my 3D model, which would be 3D points (not necessarily vertices of the mesh) with a name, for example:
"right index fingertip" 0.45 0.11 0.23
I haven’t found any specific element in the file specification that fits this. What would be the recommended way of adding this kind of information to the file?
I am not sure about what you are trying to achieve here, so let me propose a few things:
By landmark did you mean axis_up ?
if so, you have only fixed axis_up specified in COLLADA. as [X/Y/Z]_UP. (This is defined in asset page 50 of the SPEC 1.4.1).
But if you want to be really flexible, --as far as I know-- there isn’t really a way to specify a single isolated point in COLLADA as you suggest.
But you can certainly consider making a special case for a given shape or mesh where you would specify custom points (any number 1…+). Then you could identify this point using its unique ID (from the source) or if you want more custom info you could also add a <extra> tag.