How to use Parent Calibrator Patch

General Discussion
1

Hello,

Are there any sample projects or similar resources available that demonstrate how to use the Parent Calibrator Patch?

2

Multi camera calibration is documented poorly. Here is a draft for that feature.

Using a Parent Calibrator Patch

Purpose

Use a parent calibrator when one camera can see the entire projection surface.

This arrangement is useful for a dome with multiple fixed cameras around its perimeter. Each perimeter camera calibrates the projectors it can see. A central camera that sees the whole dome is then used once to calibrate the geometry between the perimeter-camera regions.

The parent/child arrangement combines the perimeter-camera calibrations into one virtual projection layer. Using the central camera, the parent calibrator calibrates the complete screen as though the regions covered by the perimeter cameras were ordinary projectors. After this relationship has been calibrated, the central camera does not need to remain in the installation.

Do not use a parent calibrator if there is no camera position from which the entire screen is visible. In that case, align the camera-calibrated regions manually or use 3D Scene remapping.

Terms

  • Child calibrator: a calibrator connected to a fixed perimeter camera. It calibrates the projectors visible to that camera.
  • Parent calibrator: the calibrator connected to the central camera. It calibrates the geometry between the combined child regions across the complete screen.
  • Calibrator Patch: the calibrated output region produced for a calibrator.
  • Blending Calibrator: a node that combines calibrator patches belonging to different camera calibrations.

Node layout

image
image1476×864 119 KB

Create additional child calibrators and blending nodes as required by the physical setup.

Setup

  1. Install the fixed perimeter cameras and verify that, together, they cover the complete screen.
  2. Place a central camera where it can see the complete screen.
  3. Create one child calibrator for each perimeter camera.
  4. Connect each child calibrator to its camera and to the projectors that camera can calibrate.
  5. Create a Calibrator Patches for each projector of child calibrator.
  6. Use Blending Calibrator nodes for all outputs. Connect child Calibrator Patches only to those Blending Calibrator nodes that is connected to projectors this camera can calibrate.
  7. Calibrate child calibrators first.
  8. Connect the parent calibrator to the central camera and configure it to calibrate the complete screen. Treat the combined child regions as the parent calibrator’s projectors.
  9. Create the required Calibrator Patch nodes for the parent calibrator.
  10. Connect each parent patch’s Patch output directly to the corresponding child calibrator’s Parent Calibrator Patch input.
  11. Run the parent calibration to align the geometry between the perimeter-camera regions - Geometry only.

Only the link in step 10 is needed to pass a parent patch to a child calibrator. Do not also recreate the source and map connections manually.

How the link behaves

During parent calibration, the parent patch is rendered to an intermediate render target and used as the source image for the child calibrator. This lets the parent display calibration patterns through the already calibrated child output.

After calibration, normal content should be sampled only once on its way to the physical projectors. Sampling the rendered parent patch again would add an unnecessary render and resampling stage. The child calibrator therefore uses the parent patch’s calibration maps directly:

  • the parent UV map supplies the child’s source UV mapping;
  • the parent blending/white map supplies the child’s external blending or white mapping;
  • the original parent source supplies the content.

Connecting a parent Calibrator Patch to Parent Calibrator Patch switches between these behaviors automatically. While the parent is calibrating or showing a test pattern, the child uses the rendered parent patch. During normal playback, it uses the source and maps directly.

Important constraints

  • Connect exactly one source to each Parent Calibrator Patch input.
  • The source must be a Calibrator Patch node.
  • Do not create a loop between parent and child calibrators.
  • A Blending Calibrator must not combine two patches from the same calibrator.
  • Complete and verify the child camera calibrations before calibrating the parent screen.
3

Thank you. I understand it well.