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Stage vs. Scene Coordinates

The stage coordinates generated by the survey tool, and then solved for by the Intersense or other tracking devices, are then routed into Previzion and converted into CG scene coordinates for correct rendering of the CG background.

In the above UI screen capture of Previzion, the highlighted area is the CG scene coordinates inside Previzion. When you click Edit, and move the camera around, or enter values into this area, you are directly adjusting the virtual camera position inside Previzion, in the coordinates of the virtual scene.

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Camera Offsets

While you do this, you will notice that the camera offset coordinates highlighted above are changing in real time. These numbers represent the offset (both translation and rotation) between the stage/tracking system coordinates, and the virtual scene coordinates inside Previzion.

 

Matched Coordinate Systems

When working on a shoot that requires accurate matching between specific live action and virtual coordinates, the only way to make it work and remain sane to designate a physical point as the origin, and build virtual sets with the same virtual origin point and the same +X axis direction. This way, the virtual and the live action worlds can be aligned very simply, by setting the camera X, Y, Z, and pan offsets to 0.

Freeform Coordinate Systems

When shooting on a blank green stage, you can freely adjust the virtual coordinate system to match. However, to ensure that the virtual floor remains connected to the live action floor, keep the Y offset value at 0, assuming that the virtual floor is located at Y=0. If the virtual floor is at a different elevation, you can set the Y offset by moving the virtual camera over the section of virtual geometry in the scene, and clicking Set Floor Offset.