Add floor

[cpinter]

Currently users have problems differentiating between "huge object very far" and "normal sized object close". This results in them unsuccessfully trying to reach out into objects that are magnitudes further than their arms can reach. The main reason for this is that they don't have any reference to which they can relate the displayed scene to.

A floor could address this problem. We talked with @lassoan about this and we think that what could work is a floor that

• Appears at the level and orientation of the physical floor at the time of starting VR
• Has the size of a larger room (~OR)
• Displays a grid that allows users to feel movement when they are near the floor
• Is mostly transparent (like stained glass) so that the user can see the parts of the scene that are below the floor (it may happen)

Floor would also allow teleport-style movement (#71)

[drouin-simon]

I would go for a whole box (room) rather than just a floor. This way, no matter where you look, you experience perspective in stereo, which is very powerful to get a sense of space.

[adamrankin]

Depending on how generous you're feeling, would you consider adding UI elements for floor/wall colour and, even crazier, texture from file?

A number of our collaborating vision scientists want this feature (not urgently, luckily).

[lassoan]

The main clue we want to give is your height (distance from floor) compared to size of displayed objects, so we will focus on that first, but we should choose a design that will allow adding walls without too much effort.

[cpinter]

See https://gitlab.kitware.com/vtk/vtk/-/merge_requests/11028

Specifically what we should look at is vtkSkybox::SetProjectionToFloor