Beamer¶

A Beamer represents a real world projector inside SPARCK's 3D space.

It has a calibration mode to find the orientation and lense properties (extrinsic and intrinsic transformations) of the projector.

It uses the opencv calibrateCamera() method to calculate the tranformation and projection matrix of a projector.

For this to work the node needs a calibration model (3D object) and a set of manually set calibration vertices that correspond to points on the calibration model.

Reference¶

The following properties can be configured for this node:

Calibration¶

CalibratorEditor

Calibration Settings

The calibration window provides advanced configuration options for projector calibration:

Parameter	Type	Description
Color	Color	Identifies the Beamer/Calibrator in the 3DViewer
Model	File	Calibration model. Needs to be of type Wavefront OBJ
use Model transformation	Toggle	Additional transformations on the calibration model to place it correctly to the world reference
implement parent transformation	Toggle	You can calibrate the beamer while attached to a mocap rigidbody that is referenced by the parent transformation node
focus editor	Button	Opens the editor window and focuses it to this calibration
gather 3DViewer lookat	Button	Takes the current 3DViewer point of view and applies it as a temporary solution
display..	Button	Opens the display window to select the display the projector is currently connected to
width	Integer [px]	Projector resolution width
height	Integer [px]	Projector resolution height
enable calibration	Toggle	Enables the calibration button. Only enable once the correct resolution is set
show/hide	Button	Shows / hides calibration flags
frustum	Display	Shows the solution's frustum
transformation	Matrix	Shows the solution's transformation matrix
reset	Button	Resets values
save and close	Button	Saves the solution and closes the calibration window

Calibration with Motion Capture

If you're calibrating while the projector is attached to a motion capture rigid body, enable implement parent transformation. This automatically calculates the local transformation offset from the rigid body to the projector's lens position.

Editor Keyboard Shortcuts

The Beamer calibration editor has three main modes for setting up projector calibration:

• Model Mode - for selecting points on the 3D calibration model
• Target Mode - for positioning corresponding points in the projector's output
• Warp Mode - for creating and adjusting warp mesh vertices
• Press Tab to switch between modes

General Controls (All Modes):

Key	Action
Tab	Switch between Model, Target, and Warp modes
H	Toggle help overlay
Shift+H	Change help overlay color
K	Toggle visibility of calibration results
L	Toggle visibility of labels

Model Mode (No Selection):

Key	Action
	Select model vertex
S	Save calibration
P	Purge calibration (requires confirmation)
J	Adjust ALL targets to warp or model vertices

Model Mode (Vertex Selected):

Key	Action
V	Create calibration vertex (both target and warp)
W	Create warp vertex linked to model vertex
T	Create target vertex linked to model vertex
X	Delete calibration vertex

Target Mode (Vertex Selected):

Key	Action
J	Adjust selected to warp or model vertex
W	Add warp vertex linked to model vertex
X	Remove target vertex
G	Grab vertex with mouse (click to confirm)
Up Down Left Right	Move vertex with arrow keys
C	Toggle crosshair mode
O	Toggle visibility of calibration object

Target Mode (Adjust Vertex Submode):

Key	Action
M	Adjust to model vertex
W	Adjust to warp vertex
Esc	Exit adjust mode

Warp Mode (No Selection):

Key	Action
	Select warp vertex
J	Adjust all to target or model vertices
W	Create unlinked warp vertex
S	Save warp object
F	Enter frame subdivision mode
D	Enter warp subdivision mode

Warp Mode (Vertex Selected):

Key	Action
	Select second vertex (for subdivision line)
J	Adjust to target or model vertex
T	Add target vertex linked to model vertex
X	Remove warp vertex
G	Grab and move vertex with mouse (click to confirm)
Up Down Left Right	Move vertex with arrow keys
0 - 9	Create subdivision line between two selected warp vertices

Warp Mode (Adjust Vertex Submode):

Key	Action
M	Adjust to model vertex
T	Adjust to target vertex
Esc	Exit adjust mode

Warp Mode (Frame Subdivision Submode):

Key	Action
0 - 9	Set frame subdivision value
Esc	Exit frame subdivision mode

Warp Mode (Warp Subdivision Submode):

Key	Action
0 - 5	Set warp subdivision (only 2 are displayed)
Esc	Exit warp subdivision mode

Model Mode (Purge Confirmation):

Key	Action
Y	Confirm purge calibration
Esc	Cancel purge operation

Save Your Work

Calibration data is saved when you press S in Model mode or when you click save and close in the calibration window. Make sure to save regularly during the calibration process.

Calibration using createToXY and addToXY¶

You can create calibration targets directly from the Beamer node using the createToXY and addToXY messages using the custom inlet.

This will create calibration targets relative to the XY-plane of the Beamer node and avoids the need for a calibration model.

This apprioach is usefull when the calibration has to happen in a space that provides tracking vertices in world space, e.g. using motion capture markers as calibration targets. The OptiiTrack node provides the 3D positions of the markers in world space that can be used as calibration targets:

Max SetupEditor

Example patcher to create calibration targets. The OptiTrack node provides the 3D positions of the mocap markers in world space from the 'dump' outlet, filtering for '/om' (other markers - markers not assigned to a rigidbody). This list is then prepended with the 'createToXY' message and sent to the Beamer's custom inlet.

This results in the following calibration targets:

Multi-Projector Setups¶

Important Notes¶

~/_assets/_projectors/          # Beamer Calibration files (.xml & .json)
~/_assets/_projectors/_calib    # Target vertex files (.xml)
~/_assets/_model/_calib         # Calibration models (.obj)

Last updated: 2024-12-01 | Edit this page on GitHub