Overview
Camera calibrations are accomplished in a series of steps. The interface guides the user to complete these steps in order while indicating when any steps are incomplete. It is possible to skip some steps and return later to complete them.
Capture Reference Frames from Game Cameras
A: Show the calibration sub menus by clicking on the “wrench” icon, select “New” calibration.
B: Next select the correct field model. Note NFL, NCAA and CFL fields are different, Fig 2.
C: Select the camera to capture using one of the three tabs (Main, Left, Right). Then click the [Capture] button to begin capturing a camera’s reference frames, Fig 3.
Virtual first can operate with one or three cameras. In typical broadcast environments, the camera at the left 25 yard line is camera 1, this camera is “Left” in the user interface. The camera at the 50 yard line is camera 2, this camera is “Main” in the user interface. The camera at the right 25 yard line is camera 3, this camera is “Right” in the user interface.
D: Direct the camera operator to set the shot that closely matches the image on the interface, then click the camera button to capture the shot, Fig 4, Fig 5.
E: Save the calibration after all frames for any camera have been captured. To do this, click the [wrench] icon (this will close the calibration sub menu). Click the [wrench] icon again to open the sub menu and click [Save As] or [Save], Fig 1. After saving, click [Edit] and navigate to the next appropriate step to resume the capture process. The saved calibration file contains all the various phases of the calibration effort. As calibration progresses, saving will write the previous images and any new images to the file.
F: Repeat steps C , D and E until all camera frames are captured, then click the [Done] button to exit the capture sub menu, then save the calibration.
IMPORTANT! Hitting [Ctrl][s] will not save the calibration, it will save the Virtual 1st project, which is a different part of Virtual 1st covered later in this document. The only way to save the calibration is to follow instructions in step E .
IMPORTANT! The far sideline must be visible in every shot. The field must be as clear of obstructions as possible (few people and no equipment on the field). Capturing frames when the lines are covered by columns of performers (band or cheerleader rehearsals) will lead to a failed or weak calibration. Avoid capturing during times when there are a lot of people or equipment on/obscuring the field.
QUICK TIP Capturing reference frames is usually faster when camera operators have the calibration shot sheet that corresponds to their camera location. Shot sheets are at the end of this document. Frame capture sessions can be accomplished in any order (for instance, camera 3 first, then camera 1, then camera 2). Capture all frames for a camera position in a single session.
QUICK TIP Virtual 1st Project (*.ppp) and Calibration (*.cal) files are separate and are stored in different locations on the system drive. Current file names can be seen in the application title bar. An asterisk (*) next to the file name indicates the file has been changed since the last save, Fig 6.
Marking Up Reference Frames
G: For each camera tab (Main, Left, Right) use the [Area] tool to crop blanking that might be present on the edges of the image. This is a single setting for each camera. The field [Color] tool rarely requires adjustment and is automatically set to green. Mark corresponding line locations using the [Lines] tool, Fig 7.
H: Mark up each frame captured. For this step, select a frame number to mark up, then select a line in the field model then draw a synthetic line over the painted line that corresponds to the line in the model. Drawing a synthetic line requires two clicks over the painted line.
I: Many frames have one or more hash marks, which are placed at the 20s and 40s respectively, that need to be selected in the field model and clicked on the field image. In this figure, the near sideline is selectable in the field model but not visible for drawing. This line can be removed by right clicking on the field model line, then click [Remove] on the pop up menu. The missing line can also be ignored but may result in an exclamation mark icon on the user interface [Lines] icon.
J: Repeat steps G , H and I for each camera, stopping to save the calibration after all (or some) frames for a camera have been marked.
QUICK TIP Marking the line locations can be a time-consuming process, taking up to 15 minutes per camera. This work can be done on any frames for any camera, as soon as they are captured (and saved) which could help save time when camera operators are not available.
K: Once the frames for the cameras have been marked, save the calibration, and click the [Calibrate] button. This starts a calculation process with its own progress bar. It could take more than a minute to run these calculations depending on the number of cameras in use. Save the calibration.
Verifying Reference Frames
L: Virtual 1st then invokes a verification process to check the quality of the calibration, automatically drawing synthetic lines over each captured frame. Step through these frames using the arrow buttons. If the synthetic lines match the painted lines on the field, that frame is considered ready for use. If the lines are off or missing, then that frame needs to be repaired.
On this frame (Fig 10), the synthetic lines generated by Virtual 1st match the painted field lines. This frame is ready to use.
On this frame (Fig 11), synthetic lines generated by Virtual 1st do not match the painted field lines. Click the repair button, redraw any lines or hash marks that are out of place, click save and [Calibrate] once again.
QUICK TIP The [Calibrate] calculation is time consuming and the verification process cannot be reentered once [Repair] has been selected. It best to review all the frames for accuracy, taking note of the frames that have failed. Users should go back into the [Lines] section to repair the failed frames. This will minimize the number of [Calibrate] operations that need to be done. Remember to save the calibration often.