Compute Page

The Compute page assists the computation of 3D information and checking computed results. It also helps to figure out the precise video synchronization parameters. This page is composed of three subpages which are described below.

Compute 3D

This subpage is forcomputing the x, y, z coordinates and the verifying computation results. This subpage contains the following elements:

• Show Invalid checkbutton: selects if all invalid points are highlighted in all Image windows.
• Show Error checkbutton: selects if all the points whose estimated coordinate errors are greater than their threshold are highlighted (green fill) in all Image windows. The error threshold field is for setting the estimated error of the computed x,y,z values of points.
• Show Strength checkbutton: selects if all the points whose estimation strengths are greater than their threshold are highlighted in all Image windows. The strength threshold field is for setting the estimation strengths of points.
• Update Display button: highlights marks according to new values entered in the fields above.
• "Compute..." button: invokes the 3D Computation Dialog for computing 3D information.

Calibrate Fixed Camera

Calibrate Fixed Camera subpage is for computing the synchronization parameters and the camera parameters when only fixed cameras are used in a motion capture project. This subpage contains the following elements:

• Frames for Calibration listbox: lists the frames in one video that is used for camera calibration.
• Add button: click it to add a video frame for calibration.
• Delete button: use it to delete a frame that is selected in the listbox.
• Clear button: it deletes all frames listed in the listbox.
• Offset checkbutton: when videos contain only a few dozen frames, the sample rate difference may not be obvious and therefore only the "offset" needs to be computed.
• Offset and Speed checkbutton: compute both "speed" and "offset" when the videos are long (more than 50 frames).
• Fixed checkbutton: select fixed points that will be used for the calibration when this checkbutton is yellow.
• Moving checkbutton: select moving points that will be used for the calibration when this checkbutton is yellow.
• Calibrate: Invokes the Calibration dialog box.

See Calibrating fixed Camera for more details.

Create Sync. Point

This subpage provides a generic video synchronization method for both dynamic and fixed camera. It may also be used as an alternative method for initial synchronization, especially for long videos, or when computing the synchronization parameters for dynamic (moving) cameras.

• Edit field: lists the current synchronization point under editing. Use the scroll button to view and select other synchronization points.
• Sync field: names the video used for synchronization. Use the scroll button to view and select other videos. The frame field is for entering the number of the particular frame that is used as the synchronization point. This frame number appears in brackets in the title bar of the Image window.
• To field: names the video that is synchronized to the sync video above. Use the scroll button to view and select other videos. Enter the frame number of the synchronization point in the frame field and enter a synchronization value in the + field. The value in the + field can be a decimal.
• Create button: used for entering a new synchronization point.
• Delete button: it deletes an existing synchronization point.
• Re-display button: changes the frame displayed in the Image window according to a new frame number entered in the Sync and To fields.
• Compute... button: invokes the Compute Adjustment dialog.
• Save button: Changes and newly created synchronization points will not be saved without pressing this button.
• Update button: If all the videos are related with 2 or more synchronization points, Photo4D will compute the synchronization parameters and update the new value in the database.

See Creating synchronization point for more details.