How To Use

  1. Create Geometry to use for knockout purposes
  2. Assign Knockout Shader in Maya
  3. Make sure geometry is embedded in scene file
  4. Export from Maya and Import into Previzion
  5. Adjust video depth in Previzion

1. Create Geometry

The technique of knockout geometry is usually needed when a virtual object needs to be occluded by an object in the video feed. In this sense it will be often necessary to survey a prop or set piece, and then create the geometry from the surveyed points.

  • Survey prop piece
  • Import the surveyed points into Maya
  • Model the object based off the survey points

2. Assign the Knockout Shader

You can find the knockoutShader.cgfx here in our list of CGFX shaders. Assign this shader to the knockout object.

3. Embed Knockout Geometry with Scene File

Previzion does not currently support knockout geometry as a loadable object separate from the scene file which means currently the scene file and knockout geometry must be in the same export file

4. Export From Maya and Load into Previzion

Make sure to export as FBX and then load the scene into Previzion. This function is in the “scenes” tab in the main interface.

5. Adjust the Video Depth in Previzion

Set the “Subject Depth” (aka. the video depth) to a distance such that all your CG elements are in front of it. In order for this shader to work, the CG elements must be rendered in front of the video background, otherwise the video will cover the entire scene!


Information on the Shader

click here

Illustrated Examples

Clean Background Plate

CG Render – Robots

Knockout Geometry Objects

Knockout Geometry with Robots

Final Composite