Coordinate Offsets
Previzion lets you move the virtual scene wherever you desire, and still have the physical camera move correctly through the scene. This is done without moving the virtual scene itself, so that all tracking data will map correctly back to the original virtual file.
The Coordinate System panel shows the current X, Y, Z, and Pan offsets. (Tilt and Roll are always taken directly from camera tracking data to avoid confusion.) As the virtual camera position is edited in the Camera panel, the XYZ Offsets will change in real time. To reset any axis to zero, click the Reset button next to it.
To pan the virtual camera without moving it, click and drag up or down on the Pan Offset box. As with other controls, fine control is achieved by holding down Control, and rapid motion by scrolling the mouse wheel. The XYZ offsets will change in real time to keep the virtual camera in the same place during the panning process.
Camera Reference Locations
When the scene’s FBX file is loaded, Previzion’s scene loader reads in all of the virtual cameras that are part of the file, and makes a list of them. Each virtual camera position can be jumped to immediately by selecting it from the Camera Reference Locations drop down menu. As before, the Tilt and Roll data is not used.
This lets a director set up a list of desired camera positions for specific shots, and store them into the FBX file for rapid use.
After the new camera reference location has been selected, make sure to set the proper Y offset to keep the virtual floor and the live action floor aligned.
If the virtual floor is located at Y = 0, click the Reset button next to the Position Y Offset. This will default to the standard Intersense vertical coordinates, which have the floor at 0 and will be correct.
If the virtual floor is located on a second floor, for example Y = 325 cm, enable the Edit Position button under the Camera panel, and drag the Position Y value until the Position Y Offset value is 325.
Angle Reference System
Many different 3D applications have different zero angles for the camera. Previzion defaults to the Motionbuilder angle reference system, where by default the virtual camera points down the +X axis.
Previzion also supports the following angle reference systems:
- OpenGL
- Softimage
- Collada Y_UP
The default Motionbuilder zero angle system works well in practice for most applications. Previzion’s data capture system uses Collada, which has its own defined coordinate system that all applications supporting Collada are required to transform into and out of properly, so this setting is independent of the software used to create the FBX background file.