Dewarping a fisheye 360 degree camera

Knowledge Base - Image Correction
01/07/2015
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Dewarping refers to the process of perspective correction of an image, to reverse the effects of geometric distortions caused by the camera lens. Most commonly known as a “Fisheye” and/or “360º” device. Dewarping allows the user to cover a wide area with a single device, but also to have a “normal” view of an otherwise distorted or reversed image.

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Top left: The original fisheye video.
Top right: A dewarped image of the same device. The green border shows the view area of the dewarped image
Bottom: A panorama overview

 

In VDG Sense, a dewarped Fisheye device will function as regular PTZ device, and can be controlled with both the Live Control panel, or by clicking and dragging the mouse inside the dewarped image. You can also utilize a 360 panoramic overview in your layouts.

 

Dewarping features

  • Dewarping a Fisheye lens into a virtual PTZ capable device
  • Dewarping a Fisheye lens into a full 360º panoramic view
  • PTZ control during playback
  • Visualize and control the view area in a Fisheye or Panoramic image
  • Serverside dewarping

 

Setup

After a fisheye device has been added to VDG Sense, you can enable the dewarping simply by going to the advanced options tab of the device and selecting the “Dewarping” checkbox. From this point, the device will act like a PTZ device and can be controlled using either the mouse or the PTZ rose in the Live Control panel.

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Manual Adjustment

As of Sense 2.4.9, it is possible to manually modify the dewarping.
When dewarping is enabled, a new subtab in the device settings will open named ‘Dewarping’. In here, you can define the edge of the camera by moving the dewarping-circle

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By default, the algorithm will try to find the ideal position of the circle when dewarping is enabled. If the automatic detection isn’t configured correctly, you can move and resize the circle manually using one of the 4 anchor points on the yellow circle. To retry the automatic detection, click the button “Detect circle” to rerun the algorithm automatic detection routine.

Dewarp algorithm
Choose between the standard algorithm VDG, or the Panomorph algorithm by Immervision.

Dewarp type
Ceiling / Wall / Floor
Depended how the camera device is installed. This will affect how the panoramic view is created and the direction of the PTZ controls

 

Layout manager: Dewarping panel

Dewarped devices will show up as a ‘PTZ dome’ when placed in a live or playback panel. If you wish to utilize the Fisheye feed in your layouts, you need to include the new Dewarping Panel in your layout.

The dewarping panel has the following functionalities:

  • Show the original Fisheye video of a dewarped device
  • Create a panoramic dewarp
  • Visualize the dewarped “viewing area” in the Fisheye or Panorama image
  • Control the PTZ of a dewarped device

The dewarping panel can also function as a live video panel and will only perform differently on devices with dewarping enabled.

 

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The dewarping panel has the following options:

  • Dewarp type
    • Panorama
      Panorama mode will create a 360º Panorama dewarp of a Fisheye device.
    • Fisheye
      Fisheye mode will show the original footage of a Fisheye device.
  • Visualize dewarping
    If enabled, a green border will be visible in the panel, indicating the view area of a dewarped device. This option will also allow the user to control the PTZ of the dewarped device by clicking and dragging in the panel.
  • Location
    Filter the device list on location.
  • Device
    Select the device that will be displayed in this panel. Note that the dewarping options will only be available for devices that have dewarping options enabled. If needed, the dewarping panel can also function as a normal Live panel.
  • OSD Style
    Set the OSD style of the dewarping panel.
  • Fit to panel
    Check to fit the video to the border of the panel. Note that this option does not work for the panorama setting, which will always fit to the width of the panel.

 

 

Layout example

Below you will find an example of a layout which utilizes the dewarping panel along with a live panel. The panels have the following configurations:

  • Panel 2 – Dewarping panel set as Panorama and Visualization enabled
  • Panel 3 – Dewarping panel set as Fisheye and Visualization enabled
  • Panel 4 – Live panel loaded with a dewarped device

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This will give the following layout in Live mode:

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Supported devices

VDG Sense dewarping algorithm currently doesn’t support Fisheye devices in which part of the visible area falls outside of the borders of the feed, creating an incomplete circle.

 


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