[osg-users] Absolute_Rf to Relative_Rf coordinates

[João]

I'm displaying some text in a 3D scene using a transform with an absolute reference frame. I now need to find out what the world coordinates of the text are, is that any way to easily obtain that information?

[Robert Osfield]

Hi Joao,

Subgraphs under a ABSOLUTE_RF Transform are effectively in their own
local world coordinate frame, they don't related to other word
coordinate frames. You can relate to them view the eye coordinate
frame if you want though, or shift them from one world coordinate
frame into eye coordinate and then back out to another world
coordinate frame so see the relative position of it.

However, doing these transforms is view dependent, as every time the
camera moves the relative positions all shift, this means you need to
keep track of the view matrix as part of the shifting the coordinate
frame from one world coordinate frame to another. Doing this may make
sense in very specific cases, but it might be that you are simply
trying to do things in an awkward way and there is a better way of
doing things without the messy hack of mixing different world
coordinate frames.

Robert.

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