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Step 3: Volumetric Capture Calibration in VolCapp

For your volumetric capture, depth camera calibration is the key. In other words, you need to combine the pointclouds into one view. It’s very hard to do by hand and that’s where EF EVE™ VolCapp auto calibration comes in very handy.

Calibration Window

When you open your Calibration tab 3D view, your pointclouds should look messy, because your cameras are not calibrated with global coordinate system yet. It should look similar to this:

Calibration window, 3D view before depth camera calibration
Calibration tab view before depth camera calibration

You can see the X, Y, Z axes and the views from your cameras are in random positions. The point of Calibration is to connect those two 2D views into one 3D view, so let’s get started.
You can control your view in this window with your mouse:

  • Rotate – left click and drag
  • Zoom in / zoom out – scroll wheel
  • Drag – click scroll wheel and drag

On your Calibration menu (at the right), you will see your auto calibration toolset (image below):

If you don’t have a business license, you will only see an option for Manual Scene Calibration. 

Depth camera marker calibration - calibrate master and slave cameras
Auto-Calibration toolset for volumetric capture

Auto Calibration

Firstly, you need to calibrate your master camera with the global coordinate system in order to have your volumetric videos stand nicely on the ground. To do do that, follow the steps below:

  • Open a 2D view and place a single calibration marker on the ground in the center of the capture stage. 

Make sure marker’s shoreline is parallel with capture stage shoreline.

Depth camera calibration marker has to be in the center of volumetric capture stage
Placing a marker in the center of volumetric capture stage.
  • After the marker is placed, open your 3D view in the Calibration tab:
3D view button on Calibration window
Calibration window 3D button on the main menu in EF EVE VolCapp.
Master camera calibration
  • To begin Master camera calibration press Start on Single Marker Calibration tool:
Press the 'start' button to initiate master marker calibration in Auto Scene Calibration section.
Initiate master camera calibration for volumetric capture

As calibration takes place you will notice a green progress bar next to Sensor 1 (Master). 

Wait till the green progress bar completes to calibrate depth camera for volumetric video
Master camera calibration in progress for volumetric capture

The Master camera pointcloud will make an automatic transition. The center of the marker will align with the center of the global coordinate system (0;0).

Calibrated Master camera for volumetric video
Calibration window view after Master camera calibration

Well done! The next step is to align Slave Camera pointcloud with the Master using Slave Calibration tool.

Slave camera calibration

To begin Slave camera pointcloud calibration press Start on Slave Calibration tool. 

Initiate slave camera pointcloud calibration
Slave camera pointcloud calibration for volumetric video

As calibration takes place you will notice a green progress bar next to both sensors:

slave camera pointcloud calibration in progress for volumetric video capture
Progress bar slave camera pointcloud calibration for volumetric video

The Slave camera pointcloud will make an automatic transition and align with the master camera pointcloud.

Volumetric capture view in EF EVE VolCapp after automatic calibration
View from calibration window after Slave camera calibration for volumetric video

At this time you have two pointclouds calibrated with the global coordinate system at a medium precision. As you want to have a high precision calibration lets use the Bounding Box Presets and Multi Marker Calibration.

Bounding Box Calibration

Bounding Box feature helps to select the capture stage and eliminate the unwanted data. We have created Bounding Box Presets to simplify the selection process as you are able to quickly change between different dimensions of the stage.

  • Scroll down to the Bounding Box Calibration section
  • Press Enable Bounding Box checkbox.
  • Press + to expand functions.
EF EVE VolCapp depth camera bounding box calibration
Bounding Box Presets for volumetric capture

For a 1m x 1m Capture Stage we recommend a MINI size Bounding Box preset.

Each Preset have dimensions next to it. Example: MINI 0.1 is 1.4 meters on 1.4 meters square and 2.3 meters in elevation from the ground (there is an additional 10 centimeters below the ground). This can be adjusted with sliders later on. As of now it will help to have the floor as a reference.

View with and without bounding box  for depth camera volumetric capture
Volumetric capture view without Bounding Box and with it. Preset MINI 0.1 is selected.

Read next: Multi-Marker Calibration

Updated on January 24, 2020

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