Export and use an ST map

You can export lens maps (ST map as a 32-bit EXR file) for calibrated video cameras from Shogun Live as distortion maps. You can then import your calibrated video camera/lens into a game engine such as Unreal, or into your compositing software.

The ST map contains information about the distortion of the lens and has four channels: R, G, B, and A:

• B and A store the location of the pixels in a pinhole/undistorted image, ranging from 0 to 1 in proportion to the width and height of the image. These two channels are used to distort the CG image to match the SDI camera output.

• R and G store the location of the pixels in a raw/distorted image (currently unused).

To use a Shogun Live ST map, the first step is to export it from Shogun Live.

See also the Vicon video How do I set up a Vicon-driven cine camera in Unreal Engine with lens distortion?

Export an ST map

1. Ensure the video camera(s) have been calibrated, then from the File menu, select Export Video Camera STMap.

   

2. In the Save Camera Distortion Map dialog box, locate a folder to which to export the ST maps.
   ST maps for all video cameras are exported to this folder.
   Each filename has the format: <Camera DeviceID>_<focal length in pixels- integer part>_<focal length in pixels - decimal part>_<date time stamp>.exr, for example, vi101_1064_535479_20210623165749.exr.

The ST map contains information about the distortion of the lens and has four channels: R,G,B,A:

• B and A store the location of the pixels in a pinhole/undistorted image, ranging from 0 to 1 in proportion to the width and height of the image. These two channels are used to distort the CG image to match the SDI camera output.

• R and G store the location of the pixels in a raw/distorted image (currently unused).

This is an example of an ST map:

You can use the exported ST maps in a number of ways, including in game engines, such as Unreal Engine, or in compositing software. The following example shows how to use the ST map to set up a live composure in Unreal Engine, using the Virtual Production template project.

Set up a live composure in Unreal Engine

1. In Unreal Engine, to import the ST map into the content, right-click to create a new subfolder in the content folder.

   

2. Browse to the new folder, right-click and select Import to /Game /Distortion Maps to import the ST map that you exported from Shogun Live.

   

3. In the Import dialog box, locate and select the ST map file.
   The ST map is displayed in the Content Browser.
   

   

4. In the Content Browser, navigate to Content > VprodProject > Maps and double-click the LiveComp map.

   

5. In the Content Browser, navigate to Content > VprodProject > Materials and double-click the M_Live_Comp material.

   

   The default graph for the material looks like this:
6. Expand the note and right-click to add a new TextureSampleParameter2D node to the graph:

   

7. Give the node an appropriate name:

   

8. With the node selected, in the Details panel, find the Material Expression Texture Base.

   

9. Click on the default texture to browse for the ST map and start typing the name of the file.

   

   The ST map image is displayed in both the Details panel and the node in the graph.

   

10. Drag from the UV's pin on the FG (foreground) node:

    

11. Add a new AppendVector node:

    

    
12. To 'undistort' the foreground layer in this example, connect in this way:

    

13. Save the asset: