Offset of Projector

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Offset of Projector
-The dome masters on this page were stitched by QuickStitcher-

The best position to see stars in a planetarium dome is the center of the dome
because the star projector and the dome screen are designed to re-create a star field
on the assumption that the view point is located at the center of the dome.

When normal dome masters are projected by a fisheye-projection-type fulldome video projector,
the projector needs to be put on the vertical center line of the dome.
That means no one can put his view point at the center of the dome.

However, if you modifiy dome masters so that they can be correctly projected from a given point
in the dome, the problem is solved, and you can shift the projector from the center of the dome.

In case that a traditional (mechanical) star projector and a fisheye-projection-type fulldome
video projector are installed together in a dome, you cannot help but shift the latter.
This modification is definitely useful in such a case.

view point offset dome master

EXAMPLE OF PROJECTOR OFFSET DOME MASTER
Projector position: (x, y, z) = (0.25, 0.2, -0.1)

coordination system

Coordination System
This is the coordinate system used here.

Comparison between Normal Dome Master (left) and Projector Offset Dome Master (Right)
Using offset dome masters, you can put your fisheye-projection-type projector anywhere in the dome.

NORMAL (NON-OFFSET) Projector position: (x, y, z) = (0.0, 0.0, 0.0)	PROJECTOR OFFSET Projector position: (x, y, z) = (0.25, 0.2, -0.1)
Normal Dome Master Put the cursor over the image to see the horizontal coordinate grid.	Offset Dome Master Put the cursor over the image to see the horizontal coordinate grid.
Projected Normal Dome Master & Viewer Viewer: (x, y, z) = (-0.6, 0.0, 0.0) The center of the dome is occupied by the projector. The viewer cannot stand at the center.	Projected Offset Dome Master & Viewer Viewer: (x, y, z) = (0.0, 0.0, 0.0) The viewer is standing at the center of the dome.
View from the Viewer (Normal Dome Master) The off-center viewer sees a distorted image.	View from the Viewer (Offset Dome Master) The viewer at the center of the dome sees an undistorted image.

Due to aberration and/or focal depth of the lens, you may not be able to shift the projector
to a large extent. But the projector offset correction is necessary to combine images
projected with a fulldome video projector and stars projected with a mechanical star projector precisely.

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