Cardboard viewer profiles

since 0.1.0 Simulation, audio and XR

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A lens does not sit in the middle of the half of the screen it looks through: it sits nearer the middle of the phone, because the two lenses are a face's width apart and a phone is wider than that. StereoViewer carries the numbers a holder differs by — how far apart the lenses are, how far the screen sits from them, how high the lens axis is above the tray, and how wide the lens lets the eye see.

Step 1: Pick a profile #

cardboardV1 is the older, narrower holder; cardboardV2 is the one most folded holders since have copied.

StereoViewer get _viewer =>
    useV1 ? StereoViewer.cardboardV1 : StereoViewer.cardboardV2;
static const _screen = StereoScreen(width: 0.13, height: 0.07);

Step 2: Apply it to the rig #

applyViewer turns a viewer's numbers and a screen's size into an off-centre frustum per eye, wider away from the nose than towards it.

_rig.applyViewer(_viewer, _screen);

Step 3: Compare the two #

// V1's lenses show less of the world than v2's wider window.
final v1 = StereoViewer.cardboardV1.projectionFor(Eye.left, _screen);
final v2 = StereoViewer.cardboardV2.projectionFor(Eye.left, _screen);
final v1Width = v1.tanRight - v1.tanLeft;
final v2Width = v2.tanRight - v2.tanLeft;

The older holder's lenses let through a narrower slice of the world than the newer one's, at the same screen — which is the whole reason the four numbers are worth carrying separately instead of guessing one frustum for every holder.