Dome Projection with Spherical Distortion Lenses and Calibrator

Last updated 7 August 2026

Calibrating a dome projected through spherical distortion lenses needs settings that differ from a normal auto-alignment: the warp is extreme, projector calibration carries more error than usual, and the screen border has to be hit exactly. These are the settings that make it work.

Requires the camera-based calibration system (Calibrator) installed on the server and correctly set up.

The procedure uses the Default Mapping on the screen surface. It must not be altered in Backstage after the Calibrator XML has been imported.

Calibrator settings

Maximise the warp mesh resolution

Decrease meshStepRangeX and meshStepRangeY in Calibrator's projector library — the smaller the value, the finer the mesh:

<Projector model="4K Projector">
      <FOV hFOV="38.05" aspect="1.777"/>
      <Shear shear="0"/>
      <LensDistortion type="nodistortion">
      </LensDistortion>
      <NativeResolution resolution="Custom" customResolutionX="4096" customResolutionY="2160" meshStepRangeX="8" meshStepRangeY="8" hiResMeshDivisor="2" refreshRate="60"/>
      <Blending gamma="2.2"/>
      <Lamp lightPower="8500.0" />
</Projector>

Do not extrapolate towards the border

Projector calibration carries considerable error here, so extrapolation works badly. To hit the screen border, set numOfEdgesToDelete to 0 in the Calibration node.

Keep the whole projector area usable

The warp is large, so TilesOutside is needed to keep using the entire projector area:

Camera masks must be perfect. Everything downstream depends on them.

Projector calibration

Place markers along the screen border, with only a few towards the top:

Force the projector calibration to an opening angle of roughly 80–90°:

Checking the result

The calibrated mesh warp should look close to the image below. More distortion than this in the output mesh means the forced hFOV during projector calibration should be increased.

An hFOV around 100° produces better corners, but increases the warp needed along the screen border — which can cost accuracy exactly where it matters most. 80–90° is the usual compromise.

Mechanical masking

The top left and right corner areas on screen must be masked mechanically, and mechanical blend mask correction applied afterwards.

Compensate Projector Blacklevel with Calibrator — black-level correction for the same kind of installation