If several projectors are used to project onto a larger surface, they must be aligned very precisely to each other in order to create the impression of a large, homogeneous image. For this purpose, it is necessary to equalize the corners of the projector and align them to each other - the so-called "warping".
In addition, the overlapping area of two projectors must be adjusted so that the impression is created as if it were only one projector - the so-called "softedge blending".

Warping and soft-edge creation can be done manually on the projectors or in softwares such as Pixera.
In both cases, however, it is a job that can take several hours, depending on the number of projectors.
The more complex the structure to be projected onto (for example, a projection into a dome or a complex 3D object), the more difficult the manual setup becomes.

A camera-supported calibration of the projectors offers a great relief here.
Here, each projector image is recorded by one or more cameras and the distortion and position is determined on the basis of test images. Afterwards these data are evaluated by the software and the warping and soft blending are calculated for each projector. If everything runs smoothly, a perfectly set-up image is obtained after the camera-based calibration.
In Pixera there are two possibilities to load such a calibration or to create it directly in Pixera via VIOSO or MPCDI files

VIOSO Camera based calibration

Vioso is a software solution that makes it possible to measure different surfaces with one camera and thus automate the warping and softedgeblending process.

VIOSO can be started directly from Pixera, information like screen, projector, output resolution and the resulting warp is automatically exchanged between PIXERA and VIOSO.

The following video shows how to measure two projectors on one screen with VIOSO using one camera.

For further information on how to use VIOSO please also have a look on their webpage Link to VIOSO and their knowledgebase Link to Knowledgebase

Before starting the Vioso calibration, it is important to change the Screen Settings to "Texture per Screen" like shown in the picture below 

In the video below the workflow of how to use VIOSO within Pixera is shown.

MPCDI 

MPCDI is a standard to describe warping and blending for projectors. It’s aimed to streamline various calibration solutions with media servers, image generating applications and projectors.

• VESA press release 23.06.2013: MPCDI first release
• VESA press release 01.06.2015: MPCDI version 2

MPCDI for separated outputs (no mosaic)

1. Change the "Selective Target Rendering" in the Inspector of the selected Screen to "Texture per Sceen"
   
   

   
   

2. Change "Selection Mode" in the "Mapping Tab" to be able to select the projection surface
   
   
   
   
3. Select the screen in the Workspace
   
   

   
   

4. In the Inspector on the right side the options for MPCDI files can be found
   
   
5. By clicking on "Load Calibration" a specific MPCDI file on the hard drive can be selected.
   
   
6. Now, the parts of the warp can be assigned to the specific projector
   
   
   
   
7. Click on "Apply Changes"
   
   
   
8. By changing back the selection mode to "projectors" and selecting the projector, the warp window in the inspector on the right indicates that a calibration file is currently loaded.

Now the output should display the loaded warp and softedge blending as well.

MPCDI for Outputs in Mosaic Mode

Sometimes it makes sense to combine all outputs of a graphics card into a mosaic. This can be necessary to improve the performance.

For further information about how to set up a mosaic, please read the article refering on "Mosaic Setup"

For further information about how to use and set up an aggregated Output in Pixera, please read the article refering on "Aggregated Output"

The workflow of using an MPCDI differs slightly to the standard worflow. Please find the necessary steps below:

1. Change the "Selective Target Rendering" in the Inspector of the selected Screen to "Texture per Sceen"
   
   
2. Change the mosaic output to "output is aggregated" - please find more information about "aggregated outputs" in the related article.
   
   
3. In the next step assign this output to all projectors involved.
   
   
4. If the MPCDI was created in such a way that it only refers to the final mosaic without splitting the outputs in it, the selection "Use Full Output" must now be selected here for each projector in the "Aggregate Output Assignemt" settings.
   
   
   
   
   This has to be done for in that case both projectors
   
   
   
5. In the next step the MPCDI file can be loaded again by selecting the screen and clicking the button "Load calibration"

Here - the same region needs to be assigned to each Projector